VIN
CIN
3 x 10 PF
RFBT
CFF 4.7 nF (OPT)
See Table
CSS
0.47 PF
(OPT)
RFBB
See Table COUT
2 x 330 PF
LMZ12008
VOUT
SS
FB
VIN
EN
PGND
VOUT
AGND
Enable
0 2 4 6 8
40
50
60
70
80
90
100
EFFICIENCY (%)
OUTPUT CURRENT (A)
6Vin
8Vin
10Vin
12Vin
16Vin
20Vin
Product
Folder
Sample &
Buy
Technical
Documents
Tools &
Software
Support &
Community
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
LMZ12008 8-A SIMPLE SWITCHER
®
Power Module With 20-V Maximum Input Voltage
1
1 Features
1• Integrated Shielded Inductor
• Simple PCB Layout
• Fixed Switching Frequency (350kHz)
• Flexible Start-up Sequencing Using External Soft-
start, Tracking and Precision Enable
• Protection Against Inrush Currents and Faults
such as Input UVLO and Output Short Circuit
• Junction Temperature Range –40°C to 125°C
• Single Exposed Pad and Standard Pinout for Easy
Mounting and Manufacturing
• Fully Enabled for WEBENCH®Power Designer
• Pin Compatible With LMZ22010/08/06,
LMZ12010/06, LMZ23610/08/06, and
LMZ13610/08/06
• Electrical Specifications
– 40-W Maximum Total Output Power
– Up to 8-A Output Current
– Input Voltage Range 6 V to 20 V
– Output Voltage Range 0.8 V to 6 V
– Efficiency up to 92%
• Performance Benefits
– High Efficiency Reduces System Heat
Generation
– Low Radiated Emissions (EMI) Tested to
EN55022
NOTE: EN 55022:2006, +A1:2007, FCC Part 15 Subpart B,
tested on Evaluation Board with EMI configuration
– Only 7 External Components
– Low Output Voltage Ripple
– No External Heat Sink Required
2 Applications
• Point-of-load Conversions from 12-V Input Rail
• Time-Critical Projects
• Space Constrained / High Thermal Requirement
Applications
• Negative Output Voltage Applications
See AN-2027 SNVA425.
3 Description
The LMZ12008 SIMPLE SWITCHER®power module
is an easy-to-use step-down DC-DC solution capable
of driving up to 8-A load. The LMZ12008 is available
in an innovative package that enhances thermal
performance and allows for hand or machine
soldering.
The LMZ12008 can accept an input voltage rail
between 6 V and 20 V and can deliver an adjustable
and highly accurate output voltage as low as 0.8 V.
The LMZ12008 only requires two external resistors
and external capacitors to complete the power
solution. The LMZ12008 is a reliable and robust
design with the following protection features: thermal
shutdown, programmable input undervoltage lockout,
output overvoltage protection, short circuit protection,
output current limit, and the device allows start-up
into a prebiased output.
Device Information(1)(2)
PART NUMBER PACKAGE BODY SIZE (NOM)
LMZ12008 NDY (11) 15.00 mm × 15.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
(2) Peak reflow temperature equals 245°C. See SNAA214 for
more details.
Simplified Application Schematic Efficiency 3.3-V Output at 25°C
2
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
Table of Contents
1 Features.................................................................. 1
2 Applications ........................................................... 1
3 Description............................................................. 1
4 Revision History..................................................... 2
5 Pin Configuration and Functions......................... 3
6 Specification........................................................... 4
6.1 Absolute Maximum Ratings ..................................... 4
6.2 ESD Ratings.............................................................. 4
6.3 Recommended Operating Conditions....................... 4
6.4 Thermal Information.................................................. 4
6.5 Electrical Characteristics........................................... 5
6.6 Typical Characteristics ............................................. 6
7 Detailed Description............................................ 14
7.1 Overview................................................................. 14
7.2 Functional Block Diagram....................................... 14
7.3 Feature Description................................................. 14
7.4 Device Functional Modes........................................ 15
8 Application and Implementation ........................ 17
8.1 Application Information............................................ 17
8.2 Typical Application ................................................. 17
9 Power Supply Recommendations...................... 23
10 Layout................................................................... 23
10.1 Layout Guidelines ................................................. 23
10.2 Layout Examples................................................... 24
10.3 Power Dissipation and Thermal Considerations... 26
10.4 Power Module SMT Guidelines ............................ 26
11 Device and Documentation Support................. 28
11.1 Device Support...................................................... 28
11.2 Documentation Support ........................................ 28
11.3 Community Resources.......................................... 28
11.4 Trademarks........................................................... 28
11.5 Electrostatic Discharge Caution............................ 28
11.6 Glossary................................................................ 28
12 Mechanical, Packaging, and Orderable
Information........................................................... 29
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision G (August 2015) to Revision H Page
• Changed pin number from 2 to 3............................................................................................................................................ 3
Changes from Revision F (October 2013) to Revision G Page
• Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional
Modes,Application and Implementation section, Power Supply Recommendations section, Layout section, Device
and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1
Changes from Revision E (March 2013) to Revision F Page
• Changed 12 mil .................................................................................................................................................................... 23
• Changed 12 mil .................................................................................................................................................................... 26
• Added Power Module SMT Guidelines................................................................................................................................. 26
PGND/EP
Connect to AGND
5 AGND
6 AGND
3 AGND
1 VIN
2 VIN
4 EN
7 FB
SS
9NC
10 VOUT
11 VOUT
8
3
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
5 Pin Configuration and Functions
NDY Package
11-Pin
Top View
Pin Functions
PIN TYPE DESCRIPTION
NAME NO.
AGND 3 Ground Analog Ground — Reference point for all stated voltages. Must be externally connected to
PGND(EP).
5
6
EN 4 Analog Enable — Input to the precision enable comparator. Rising threshold is 1.274 V typical. Once
the module is enabled, a 13-µA source current is internally activated to facilitate programmable
hysteresis.
FB 7 Analog Feedback — Internally connected to the regulation amplifier and overvoltage comparator. The
regulation reference point is 0.795 V at this input pin. Connect the feedback resistor divider
between VOUT and AGND to set the output voltage.
NC 9 — No Connect — This pin must remain floating, do not ground.
PGND — Ground Exposed Pad / Power Ground — Electrical path for the power circuits within the module. PGND
is not internally connected to AGND (pin 5,6). Must be electrically connected to pins 5 and 6
external to the package. The exposed pad is also used to dissipate heat from the package
during operation. Use one hundred 12 mil thermal vias from top to bottom copper for best
thermal performance.
SS 8 Analog Soft-Start/Track Input — To extend the 1.6-ms internal soft-start connect an external soft-start
capacitor. For tracking connect to an external resistive divider connected to a higher priority
supply rail. See Detailed Design Procedure section.
VIN 1 Power Input supply — Nominal operating range is 6 V to 20 V. A small amount of internal capacitance
is contained within the package assembly. Additional external input capacitance is required
between this pin and the exposed pad (PGND).
2
VOUT 10 Power Output Voltage — Output from the internal inductor. Connect the output capacitor between this
pin and exposed pad (PGND).
11
4
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
(3) For soldering specifications, refer to the following document: SNOA549
6 Specification
6.1 Absolute Maximum Ratings (1)(2)(3)
MIN MAX UNIT
VIN to PGND –0.3 24 V
EN to AGND –0.3 5.5 V
SS, FB to AGND –0.3 2.5 V
AGND to PGND –0.3 0.3 V
Junction Temperature 150 °C
Peak Reflow Case Temperature (30 sec) 245 °C
Storage Temperature, Tstg –65 150 °C
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
6.2 ESD Ratings VALUE UNIT
V(ESD) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000 V
(1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which
operation of the device is intended to be functional. For ensured specifications and test conditions, see the Electrical Characteristics.
6.3 Recommended Operating Conditions(1)
MIN MAX UNIT
VIN 6 20 V
EN 0 5 V
Operation Junction Temperature −40 125 °C
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
6.4 Thermal Information
THERMAL METRIC(1) LMZ12008
UNITNDY
11 PINS
RθJA Junction-to-ambient thermal
resistance
Natural Convection 9.9 °C/W225 LFPM 6.8
500 LFPM 5.2
RθJC(top) Junction-to-case (top) thermal resistance 1.0 °C/W
5
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
(1) EN 55022:2006, +A1:2007, FCC Part 15 Subpart B, tested on Evaluation Board with EMI configuration
(2) Min and Max limits are 100% production tested at 25°C. Limits over the operating temperature range are ensured through correlation
using Statistical Quality Control (SQC) methods. Limits are used to calculate Average Outgoing Quality Level (AOQL).
(3) Typical numbers are at 25°C and represent the most likely parametric norm.
(4) Refer to BOM in Table 1.
6.5 Electrical Characteristics
Limits are for TJ= 25°C unless otherwise specified. Minimum and Maximum limits are ensured through test, design or
statistical correlation. Typical values represent the most likely parametric norm at TJ= 25°C, and are provided for reference
purposes only. Unless otherwise stated the following conditions apply: VIN = 12V, VOUT = 3.3V(1)
PARAMETER TEST CONDITIONS MIN(2) TYP(3) MAX(2) UNIT
SYSTEM PARAMETERS
ENABLE CONTROL
VEN EN threshold VEN rising 1.274 V
over the junction temperature
(TJ) range of –40°C to +125°C 1.096 1.452
IEN-HYS EN hysteresis source
current VEN > 1.274 V 13 µA
SOFT-START
ISS SS source current VSS = 0 V 50 µA
over the junction temperature
(TJ) range of –40°C to +125°C 40 60
tSS Internal soft-start interval 1.6 msec
CURRENT LIMIT
ICL Current limit threshold DC average 10.5 A
INTERNAL SWITCHING OSCILLATOR
fosc Free-running oscillator
frequency 314 359 404 kHz
REGULATION AND OVERVOLTAGE COMPARATOR
VFB In-regulation feedback
voltage VSS >+ 0.8 V
IO= 8 A
0.795 V
over the junction temperature
(TJ) range of –40°C to +125°C 0.775 0.815
VFB-OV Feedback overvoltage
protection threshold 0.86 V
IFB Feedback input bias
current 5 nA
IQNon-Switching Quiescent
Current 3 mA
ISD Shutdown Quiescent
Current VEN = 0 V 32 μA
Dmax Maximum Duty Factor 85%
THERMAL CHARACTERISTICS
TSD Thermal Shutdown Rising 165 °C
TSD-HYST Thermal shutdown
hysteresis Falling 15 °C
PERFORMANCE PARAMETERS(4)
ΔVOOutput voltage ripple BW at 20 MHz 24 mVPP
ΔVO/ΔVIN Line regulation VIN = 12 V to 20 V, IOUT= 8 A ±0.2%
ΔVO/ΔIOUT Load regulation VIN = 12 V, IOUT= 0.001 A to 8 A 1 mV/A
ηPeak efficiency VIN = 12 V VOUT = 3.3 V, IOUT = 5 A 89.5%
ηFull load efficiency VIN = 12 V VOUT = 3.3 V, IOUT = 8 A 88.5%
0 2 4 6 8
30
40
50
60
70
80
90
100
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSIPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
40
50
60
70
80
90
100
EFFICIENCY (%)
OUTPUT CURRENT (A)
6Vin
8Vin
10Vin
12Vin
16Vin
20Vin
0 2 4 6 8
0
2
4
6
8
DISSIPATION (W)
OUTPUT CURRENT (A)
6Vin
8Vin
10Vin
12Vin
16Vin
20Vin
0 2 4 6 8
40
50
60
70
80
90
100
EFFICIENCY (%)
OUTPUT CURRENT (A)
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSIPATION (W)
OUTPUT CURRENT (A)
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
6
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
6.6 Typical Characteristics
Unless otherwise specified, the following conditions apply: VIN = 12 V; CIN = three × 10 μF + 47-nF X7R Ceramic; COUT = two
× 330-μF Specialty Polymer + 47-µF Ceramic + 47-nF Ceramic; CFF = 4.7 nF; TA= 25° C for waveforms. All indicated
temperatures are ambient.
Figure 1. Efficiency 5-V Output at 25°C Figure 2. Dissipation 5-V Output at 25°C
Figure 3. Efficiency 3.3-V Output at 25°C Figure 4. Dissipation 3.3-V Output at 25°C
Figure 5. Efficiency 2.5-V Output at 25°C Figure 6. Dissipation 2.5-V Output at 25°C
0 2 4 6 8
20
30
40
50
60
70
80
90
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSIPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
10
20
30
40
50
60
70
80
90
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
DISSIPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
20
30
40
50
60
70
80
90
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
DISSIPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
7
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
Typical Characteristics (continued)
Unless otherwise specified, the following conditions apply: VIN = 12 V; CIN = three × 10 μF + 47-nF X7R Ceramic; COUT = two
× 330-μF Specialty Polymer + 47-µF Ceramic + 47-nF Ceramic; CFF = 4.7 nF; TA= 25° C for waveforms. All indicated
temperatures are ambient.
Figure 7. Efficiency 1.8-V Output at 25°C Figure 8. Dissipation 1.8-V Output at 25°C
Figure 9. Efficiency 1.5-V Output at 25°C Figure 10. Dissipation 1.5-V Output at 25°C
Figure 11. Efficiency 1.2-V Output at 25°C Figure 12. Dissipation 1.2-V Output at 25°C
0 2 4 6 8
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSIPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
30
40
50
60
70
80
90
100
EFFICIENCY (%)
OUTPUT CURRENT (A)
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
9
DISSIPATION (W)
OUTPUT CURRENT (A)
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
10
20
30
40
50
60
70
80
90
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
DISSIPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
8
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
Typical Characteristics (continued)
Unless otherwise specified, the following conditions apply: VIN = 12 V; CIN = three × 10 μF + 47-nF X7R Ceramic; COUT = two
× 330-μF Specialty Polymer + 47-µF Ceramic + 47-nF Ceramic; CFF = 4.7 nF; TA= 25° C for waveforms. All indicated
temperatures are ambient.
Figure 13. Efficiency 1-V Output at 25°C Figure 14. Dissipation 1-V Output at 25°C
Figure 15. Efficiency 5-V Output at 85°C Figure 16. Dissipation 5-V Output at 85°C
Figure 17. Efficiency 3.3-V Output at 85°C Figure 18. Dissipation 3.3-V Output at 85°C
0 2 4 6 8
10
20
30
40
50
60
70
80
90
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
10
20
30
40
50
60
70
80
90
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
20
30
40
50
60
70
80
90
100
EFFICIECNY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSIPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
9
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
Typical Characteristics (continued)
Unless otherwise specified, the following conditions apply: VIN = 12 V; CIN = three × 10 μF + 47-nF X7R Ceramic; COUT = two
× 330-μF Specialty Polymer + 47-µF Ceramic + 47-nF Ceramic; CFF = 4.7 nF; TA= 25° C for waveforms. All indicated
temperatures are ambient.
Figure 19. Efficiency 2.5-V Output at 85°C Figure 20. Dissipation 2.5-V Output at 85°C
Figure 21. Efficiency 1.8-V Output at 85°C Figure 22. Dissipation 1.8-V Output at 85°C
Figure 23. Efficiency 1.5-V Output at 85°C Figure 24. Dissipation 1.5-V Output at 85°C
0 1 2 3 4 5 6 7 8
0.998
0.999
1.000
1.001
1.002
NORMALIZED VOUT (V/V)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
20 40 60 80 100 120
0
2
4
6
8
10
MAXIMUM OUTPUT CURRENT (A)
TEMPERATURE (C)
JA = 9.9 °C/W
JA = 6.8 °C/W
JA = 5.2 °C/W
0 2 4 6 8
10
20
30
40
50
60
70
80
90
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
10
20
30
40
50
60
70
80
90
EFFICIENCY (%)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
0 2 4 6 8
0
1
2
3
4
5
6
7
8
DISSIPATION (W)
OUTPUT CURRENT (A)
6 Vin
8 Vin
10 Vin
12 Vin
16 Vin
20 Vin
10
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
Typical Characteristics (continued)
Unless otherwise specified, the following conditions apply: VIN = 12 V; CIN = three × 10 μF + 47-nF X7R Ceramic; COUT = two
× 330-μF Specialty Polymer + 47-µF Ceramic + 47-nF Ceramic; CFF = 4.7 nF; TA= 25° C for waveforms. All indicated
temperatures are ambient.
Figure 25. Efficiency 1.2-V Output at 85°C Figure 26. Dissipation 1.2-V Output at 85°C
Figure 27. Efficiency 1-V Output at 85°C Figure 28. Dissipation 1-V Output at 85°C
VOUT = 3.3 V
Figure 29. Normalized Line and Load Regulation
VIN = 12 V, VOUT = 5 V
Figure 30. Thermal Derating
20 40 60 80 100 120
0
2
4
6
8
10
MAXIMUM OUTPUT CURRENT (A)
TEMPERATURE (C)
JA = 9.9 °C/W
JA = 6.8 °C/W
JA = 5.2 °C/W
0 2 4 6 8 10 12
3
6
9
12
15
18
21
24
27
30
THETA JA (°C/W)
COPPER AREA (in2)
2 Layer 0 LFPM
2 Layer 225 LFPM
4 Layer 0 LFPM
4 Layer 225 LFPM
11
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
Typical Characteristics (continued)
Unless otherwise specified, the following conditions apply: VIN = 12 V; CIN = three × 10 μF + 47-nF X7R Ceramic; COUT = two
× 330-μF Specialty Polymer + 47-µF Ceramic + 47-nF Ceramic; CFF = 4.7 nF; TA= 25° C for waveforms. All indicated
temperatures are ambient.
VIN = 12 V, VOUT = 3.3 V
Figure 31. Thermal Derating Figure 32. θJA vs Copper Heat Sinking Area
12 VIN, 5 VOUT at Full Load, BW = 20 MHz
Figure 33. Output Ripple
12 VIN, 5 VOUT at Full Load, BW = 250 MHz
Figure 34. Output Ripple
12 VIN, 3.3 VOUT at Full Load, BW = 20 MHz
Figure 35. Output Ripple
12 VIN, 3.3 VOUT at Full Load, BW = 250 MHz
Figure 36. Output Ripple
12
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
Typical Characteristics (continued)
Unless otherwise specified, the following conditions apply: VIN = 12 V; CIN = three × 10 μF + 47-nF X7R Ceramic; COUT = two
× 330-μF Specialty Polymer + 47-µF Ceramic + 47-nF Ceramic; CFF = 4.7 nF; TA= 25° C for waveforms. All indicated
temperatures are ambient.
12 VIN, 1.2 VOUT at Full Load, BW = 20 MHz
Figure 37. Output Ripple
12 VIN, 1.2 VOUT at Full Load, BW = 250 MHz
Figure 38. Output Ripple
12 VIN, 5 VOUT 1- to 8-A Step
Figure 39. Transient Response
12 VIN, 3.3 VOUT 1- to 8-A Step
Figure 40. Transient Response
12 VIN, 1.2 VOUT 1- to 8-A Step
Figure 41. Transient Response Figure 42. Short Circuit Current vs Input Voltage
13
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
Typical Characteristics (continued)
Unless otherwise specified, the following conditions apply: VIN = 12 V; CIN = three × 10 μF + 47-nF X7R Ceramic; COUT = two
× 330-μF Specialty Polymer + 47-µF Ceramic + 47-nF Ceramic; CFF = 4.7 nF; TA= 25° C for waveforms. All indicated
temperatures are ambient.
No CSS
Figure 43. 3.3 VOUT Soft-Start
CSS = 0.47 µF
Figure 44. 3.3 VOUT Soft-Start
1 3
FB
1
2 3
Linear
Regulator
2M
2.2 uH
CBST
EN
AGND Regulator IC
CSS
Internal Passives
VOUT
CINint
COUT
EP/
PGND
Comp
CIN
RFBB
SS
VREF
2 3
VIN
350 kHz
PWM
RFBT
14
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
7 Detailed Description
7.1 Overview
The architecture used is an internally compensated emulated peak current mode control, based on a monolithic
synchronous SIMPLE SWITCHER core capable of supporting high load currents. The output voltage is
maintained through feedback compared with an internal 0.8-V reference. For emulated peak current-mode, the
valley current is sampled on the down-slope of the inductor current. This is used as the DC value of current to
start the next cycle.
The primary application for emulated peak current-mode is high input voltage to low output voltage operating at a
narrow duty cycle. By sampling the inductor current at the end of the switching cycle and adding an external
ramp, the minimum ON-time can be significantly reduced, without the need for blanking or filtering which is
normally required for peak current-mode control.
7.2 Functional Block Diagram
7.3 Feature Description
7.3.1 Output Overvoltage Protection
If the voltage at FB is greater than a 0.86-V internal reference, the output of the error amplifier is pulled toward
ground, causing VOUT to fall.
7.3.2 Current Limit
The LMZ12008 is protected by both low-side (LS) and high-side (HS) current limit circuitry. The LS current limit
detection is carried out during the OFF-time by monitoring the current through the LS synchronous MOSFET.
Referring to the Functional Block Diagram, when the top MOSFET is turned off, the inductor current flows
through the load, the PGND pin and the internal synchronous MOSFET. If this current exceeds 13 A (typical) the
current limit comparator disables the start of the next switching period. Switching cycles are prohibited until
current drops below the limit.
NOTE
DC current limit is dependent on duty cycle as illustrated in the graph in the Typical
Characteristics section.
15
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
Feature Description (continued)
The HS current limit monitors the current of top side MOSFET. Once HS current limit is detected (16 A typical) ,
the HS MOSFET is shutoff immediately, until the next cycle. Exceeding HS current limit causes VOUT to fall.
Typical behavior of exceeding LS current limit is that fSW drops to 1/2 of the operating frequency.
7.3.3 Thermal Protection
The junction temperature of the LMZ12008 must not be allowed to exceed its maximum ratings. Thermal
protection is implemented by an internal Thermal Shutdown circuit which activates at 165°C (typical) causing the
device to enter a low power standby state. In this state the main MOSFET remains off causing VOUT to fall, and
additionally the CSS capacitor is discharged to ground. Thermal protection helps prevent catastrophic failures for
accidental device overheating. When the junction temperature falls back below 150°C (typical hysteresis = 15°C)
the SS pin is released, VOUT rises smoothly, and normal operation resumes.
Applications requiring maximum output current especially those at high input voltage may require additional
derating at elevated temperatures.
7.3.4 Prebiased Start-Up
The LMZ12008 will properly start up into a prebiased output. This start-up situation is common in multiple rail
logic applications where current paths may exist between different power rails during the start-up sequence.
Figure 45 shows proper behavior in this mode. Trace one is Enable going high. Trace two is 1.8-V prebias rising
to 3.3 V. Trace three is the SS voltage with a CSS= 0.47 µF. Rise-time determined by CSS.
Figure 45. Prebiased Start-Up
7.4 Device Functional Modes
7.4.1 Discontinuous Conduction and Continuous Conduction Modes
At light load the regulator will operate in discontinuous conduction mode (DCM). With load currents above the
critical conduction point, it will operate in continuous conduction mode (CCM). When operating in DCM, inductor
current is maintained to an average value equaling IOUT. In DCM the low-side switch will turn off when the
inductor current falls to zero, this causes the inductor current to resonate. Although it is in DCM, the current is
allowed to go slightly negative to charge the bootstrap capacitor.
In CCM, current flows through the inductor through the entire switching cycle and never falls to zero during the
OFF-time.
'iL =(VIN - VOUT) x D
L x fSW
IDCB = (VIN - VOUT) x D
2 x L x fSW
16
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
Device Functional Modes (continued)
Figure 46 is a comparison pair of waveforms showing both the CCM (upper) and DCM operating modes.
VIN = 12 V, VO= 3.3 V, IO= 3 A / 0.3 A
Figure 46. CCM and DCM Operating Modes
The approximate formula for determining the DCM/CCM boundary is as follows:
(1)
The inductor internal to the module is 2.2 μH. This value was chosen as a good balance between low and high
input voltage applications. The main parameter affected by the inductor is the amplitude of the inductor ripple
current (ΔiL). ΔiLcan be calculated with:
where
• VIN is the maximum input voltage
• and fSW is typically 359 kHz. (2)
If the output current IOUT is determined by assuming that IOUT = IL, the higher and lower peak of ΔiLcan be
determined.
CIN1
RFBT
CSS
RFBB
SS
FB
EN
PGND
VOUT
AGND
VIN
VOUT
LMZ12008
LOAD
VIN
CIN6
(OPT)
CO3, 4
CIN5
(OPT)
+
CIN2,3,4 CO1
(OPT)
CO2
(OPT)
CO5
(OPT)
RENB
RENT
D1
5.1V
(OPT)
17
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LMZ12008 is a step-down DC-to-DC power module. It is typically used to convert a higher DC voltage to a
lower DC voltage with a maximum output current of 8 A. The following design procedure can be used to select
components for the LMZ12008. Alternately, the WEBENCH software may be used to generate complete designs.
When generating a design, the WEBENCH software uses iterative design procedure and accesses
comprehensive databases of components. Please go to www.ti.com for more details.
8.2 Typical Application
Figure 47. Typical Application Schematic Diagram
8.2.1 Design Requirements
For this example the following application parameters exist.
• VIN Range = Up to 20 V
• VOUT =0.8Vto6V
• IOUT =8A
8.2.2 Detailed Design Procedure
The LMZ12008 is fully supported by WEBENCH which offers: component selection, electrical and thermal
simulations. Additionally, there are both evaluation and demonstration boards that may be used as a starting
point for design. The following list of steps can be used to manually design the LMZ12008 application.
All references to values refer to the typical applications schematic Figure 47.
1. Select minimum operating VIN with enable divider resistors
2. Program VOUT with FB resistor divider selection
3. Select COUT
4. Select CIN
5. Determine module power dissipation
6. Layout PCB for required thermal performance
8.2.2.1 Enable Divider, RENT, RENB and RENH Selection
Internal to the module is a 2-MΩpullup resistor connected from VIN to Enable. For applications not requiring
precision undervoltage lockout (UVLO), the Enable input may be left open circuit and the internal resistor will
always enable the module. In such case, the internal UVLO occurs typically at 4.3V (VIN rising).
ENABLE
2.0M
13 PA
INT-VCC (5V)
1.274V
RUN
12.7k
RENB
42.2k
RENT
VIN
100:
RENH
5.1V
18
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
Typical Application (continued)
In applications with separate supervisory circuits Enable can be directly interfaced to a logic source. In the case
of sequencing supplies, the divider is connected to a rail that becomes active earlier in the power-up cycle than
the LMZ12008 output rail.
Enable provides a precise 1.274-V threshold to allow direct logic drive or connection to a voltage divider from a
higher enable voltage such as VIN. Additionally there is 13 μA (typical) of switched offset current allowing
programmable hysteresis. See Figure 48.
The function of the enable divider is to allow the designer to choose an input voltage below which the circuit will
be disabled. This implements the feature of a programmable UVLO. The two resistors must be chosen based on
the following ratio:
RENT / RENB = (VIN UVLO / 1.274 V) – 1 (3)
The LMZ12008 typical application shows 12.7 kΩfor RENB and 42.2 kΩfor RENT resulting in a rising UVLO of
5.51 V. This divider presents 4.62 V to the EN input when VIN is raised to 20 V. This upper voltage must always
be checked, making sure that it never exceeds the Abs Max 5.5-V limit for Enable. A 5.1-V Zener clamp can be
applied in cases where the upper voltage would exceed the EN input's range of operation. The Zener clamp is
not required if the target application prohibits the maximum Enable input voltage from being exceeded.
Additional enable voltage hysteresis can be added with the inclusion of RENH. It is possible to select values for
RENT and RENB such that RENH is a value of zero allowing it to be omitted from the design.
Rising threshold can be calculated as follows:
VEN(rising) = 1.274 ( 1 + (RENT|| 2 meg)/ RENB) (4)
Whereas the falling threshold level can be calculated using:
VEN(falling) = VEN(rising) – 13 µA ( RENT|| 2 meg || RENTB + RENH ) (5)
Figure 48. Enable Input Detail
8.2.2.2 Output Voltage Selection
Output voltage is determined by a divider of two resistors connected between VOUT and AGND. The midpoint of
the divider is connected to the FB input.
The regulated output voltage determined by the external divider resistors RFBT and RFBB is:
VOUT = 0.795 V × (1 + RFBT / RFBB) (6)
Rearranging terms; the ratio of the feedback resistors for a desired output voltage is:
RFBT / RFBB = (VOUT / 0.795V) – 1 (7)
These resistors must generally be chosen from values in the range of 1.0 kΩto 10.0 kΩ.
For VOUT = 0.8 V the FB pin can be connected to the output directly and RFBB can be set to 8.06 kΩto provide
minimum output load.
Table 1 lists the values for RFBT , and RFBB.
19
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
Typical Application (continued)
Table 1. Typical Application Bill of Materials
REF DES DESCRIPTION CASE SIZE MANUFACTURER MANUFACTURER P/N
U1 SIMPLE SWITCHER PFM-11 Texas Instruments LMZ12008TZ
CIN1,6 (OPT) 0.047 µF, 50 V, X7R 1206 Yageo America CC1206KRX7R9BB473
CIN2,3,4 10 µF, 50 V, X7R 1210 Taiyo Yuden UMK325BJ106MM-T
CIN5 (OPT) CAP, AL, 150 µF, 50 V Radial G Panasonic EEE-FK1H151P
CO1,5 (OPT) 0.047 µF, 50 V, X7R 1206 Yageo America CC1206KRX7R9BB473
CO2 (OPT) 47 µF, 10 V, X7R 1210 Murata GRM32ER61A476KE20L
CO3,4 330 μF, 6.3 V, 0.015 ΩCAPSMT_6_UE Kemet T520D337M006ATE015
RFBT 3.32 kΩ0805 Panasonic ERJ-6ENF3321V
RFBB 1.07 kΩ0805 Panasonic ERJ-6ENF1071V
RENT 42.2 kΩ0805 Panasonic ERJ-6ENF4222V
RENB 12.7 kΩ0805 Panasonic ERJ-6ENF1272V
CSS 0.47 μF, ±10%, X7R, 16 V 0805 AVX 0805YC474KAT2A
D1 (OPT) 5.1 V, 0.5 W SOD-123 Diodes Inc. MMSZ5231BS-7-F
8.2.2.3 Soft-Start Capacitor Selection
Programmable soft-start permits the regulator to slowly ramp to its steady-state operating point after being
enabled, thereby reducing current inrush from the input supply and slowing the output voltage rise-time.
Upon turnon, after all UVLO conditions have been passed, an internal 1.6-ms circuit slowly ramps the SS input to
implement internal soft start. If 1.6 ms is an adequate turnon time then the Css capacitor can be left unpopulated.
Longer soft-start periods are achieved by adding an external capacitor to this input.
Soft-start duration is given by the formula:
tSS = VREF × CSS / Iss = 0.795 V × CSS / 50 µA (8)
This equation can be rearranged as follows:
CSS = tSS × 50 μA / 0.795 V (9)
Using a 0.22-μF capacitor results in 3.5-ms typical soft-start duration; and 0.47-μF results in 7.5 ms typical. 0.47
μF is a recommended initial value.
As the soft-start input exceeds 0.795 V the output of the power stage will be in regulation and the 50-μA current
is deactivated. The following conditions will reset the soft-start capacitor by discharging the SS input to ground
with an internal current sink.
• The Enable input being pulled low
• A thermal shutdown condition
• VIN falling below 4.3 V (typical) and triggering the VCC UVLO
8.2.2.4 Tracking Supply Divider Option
The tracking function allows the module to be connected as a slave supply to a primary voltage rail (often the
3.3-V system rail) where the slave module output voltage is lower than that of the master. Proper configuration
allows the slave rail to power up coincident with the master rail such that the voltage difference between the rails
during ramp-up is small (that is, < 0.15 V typical). The values for the tracking resistive divider must be selected
such that the effect of the internal 50-µA current source is minimized. In most cases the ratio of the tracking
divider resistors is the same as the ratio of the output voltage setting divider. Proper operation in tracking mode
dictates the soft-start time of the slave rail be shorter than the master rail; a condition that is easy to satisfy since
the CSS cap is replaced by RTKB. The tracking function is only supported for the power up interval of the master
supply; once the SS/TRK rises past 0.795 V the input is no longer enabled and the 50-µA internal current source
is switched off.
7A
COUTt (0.165V - 7A x 0.003) x ( )
350e3
3.3V
t458 PF
Istep
COUTt
('VOUT - ISTEP x ESR) x ( )
fSW
VOUT
1.07k
Rfbb
2.26k
Rfbt
107
Rtkb
226
Rtkt
SS
3.3V Master
FB
2.5Vout
50 PA
Int VCC
20
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
Figure 49. Tracking Option Input Detail
8.2.2.5 COUT Selection
None of the required COUT output capacitance is contained within the module. A minimum value ranging from 330
μF for 6-VOUT to 660 μF for 1.2-VOUT applications is required based on the values of internal compensation in the
error amplifier. These minimum values can be decreased if the effective capacitor ESR is higher than 15 mΩ.
A Low ESR (15 mΩ) tantalum, organic semiconductor or specialty polymer capacitor types in parallel with a 47-
nF X7R ceramic capacitor for high-frequency noise reduction is recommended for obtaining lowest ripple. The
output capacitor COUT may consist of several capacitors in parallel placed in close proximity to the module. The
output voltage ripple of the module depends on the equivalent series resistance (ESR) of the capacitor bank, and
can be calculated by multiplying the ripple current of the module by the effective impedance of your chosen
output capacitors (for ripple current calculation, see Equation 2. Electrolytic capacitors will have large ESR and
lead to larger output ripple than ceramic or polymer types. For this reason a combination of ceramic and polymer
capacitors is recommended for low output ripple performance.
The output capacitor assembly must also meet the worst case ripple current rating of ΔiL, as calculated in
Equation 2 below. Loop response verification is also valuable to confirm closed loop behavior.
For applications with dynamic load steps; Equation 10 provides a good first pass approximation of COUT for load
transient requirements.
(10)
For 12 VIN, 3.3 VOUT, a transient voltage of 5% of VOUT = 0.165 V (ΔVOUT), a 7A load step (ISTEP), an output
capacitor effective ESR of 3 mΩ, and a switching frequency of 350 kHz (fSW):
(11)
NOTE
The stability requirement for minimum output capacitance must always be met.
One recommended output capacitor combination is two 330-μF, 15-mΩESR tantalum polymer capacitors
connected in parallel with a 47-µF 6.3-V X5R ceramic. This combination provides excellent performance that may
exceed the requirements of certain applications. Additionally some small 47-nF ceramic capacitors can be used
for high frequency EMI suppression.
CIN 8350 kHz x 200mV 8 22.4µF
3.3V
12V
3.3V
12V ¹
·
©
§
¹
·
©
§
8A x x 1 -
CIN 8IOUT x D x (1 - D)
fSW x 'VIN
ICIN-RMS = IOUT xD(1-D)
21
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
8.2.2.6 CIN Selection
The LMZ12008 module contains two internal ceramic input capacitors. Additional input capacitance is required
external to the module to handle the input ripple current of the application. The input capacitor can be several
capacitors in parallel. This input capacitance must be located in very close proximity to the module. Input
capacitor selection is generally directed to satisfy the input ripple current requirements rather than by
capacitance value. Input ripple current rating is dictated by Equation 12:
where
• D ≊VOUT / VIN (12)
As a point of reference, the worst case ripple current will occur when the module is presented with full load
current and when VIN = 2 × VOUT.
Recommended minimum input capacitance is 30-µF X7R (or X5R) ceramic with a voltage rating at least 25%
higher than the maximum applied input voltage for the application. TI also recommends to pay attention to the
voltage and temperature derating of the capacitor selected.
NOTE
Ripple current rating of ceramic capacitors may be missing from the capacitor data sheet
and you may have to contact the capacitor manufacturer for this parameter.
If the system design requires a certain minimum value of peak-to-peak input ripple voltage (ΔVIN) to be
maintained then Equation 13 may be used.
(13)
If ΔVIN is 200 mV or 1.66% of VIN for a 12-V input to 3.3-V output application and fSW = 350 kHz then:
(14)
Additional bulk capacitance with higher ESR may be required to damp any resonant effects of the input
capacitance and parasitic inductance of the incoming supply lines. The LMZ12008 typical applications schematic
and evaluation board include a 150-μF 50-V aluminum capacitor for this function. There are many situations
where this capacitor is not necessary.
0 1002003004005006007008009001000
0
5
10
15
20
25
30
35
40
45
50
AMPLITUDE (dBV/m)
FREQUENCY (MHz)
Horizontal Peak
Vertical Peak
Class B Limit
Class A Limit
0 1 2 3 4 5 6 7 8
40
50
60
70
80
90
100
EFFICIENCY (%)
OUTPUT CURRENT (A)
12Vin
20 30 40 50 60 70 80 90 100110120
0
2
4
6
8
10
OUTPUT CURRENT (A)
AMBIENT TEMPERATURE (°C)
JA = 9.9 °C/W
22
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
8.2.3 Application Curves
VIN = 12 V, VOUT = 3.3 V Figure 50. Efficiency VIN = 12 V, VOUT = 3.3 V
Figure 51. Thermal Derating Curve
VIN = 12 V, VOUT = 5 V,
IOUT = 8 A
Figure 52. Radiated EMI (EN 55022)
23
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
9 Power Supply Recommendations
The LMZ12008 device is designed to operate from an input voltage supply range between 6 V and 20 V. This
input supply must be well regulated and able to withstand maximum input current and maintain a stable voltage.
The resistance of the input supply rail must be low enough that an input current transient does not cause a high
enough drop at the LMZ12008 supply voltage that can cause a false UVLO fault triggering and system reset. If
the input supply is more than a few inches from the LMZ12008, additional bulk capacitance may be required in
addition to the ceramic bypass capacitors. The amount of bulk capacitance is not critical, but a 47-μF or 100-μF
electrolytic capacitor is a typical choice.
10 Layout
10.1 Layout Guidelines
PCB layout is an important part of DC-DC converter design. Poor board layout can disrupt the performance of a
DC-DC converter and surrounding circuitry by contributing to EMI, ground bounce and resistive voltage drop in
the traces. These can send erroneous signals to the DC-DC converter resulting in poor regulation or instability.
Good layout can be implemented by following a few simple design rules. A good layout example is shown in
Figure 55
1. Minimize area of switched current loops.
From an EMI reduction standpoint, it is imperative to minimize the high di/dt paths during PCB layout as
shown in Figure 53. The high current loops that do not overlap have high di/dt content that will cause
observable high frequency noise on the output pin if the input capacitor (CIN) is placed at a distance away
from the LMZ12008. Therefore place CIN as close as possible to the LMZ12008 VIN and PGND exposed
pad. This will minimize the high di/dt area and reduce radiated EMI. Additionally, grounding for both the input
and output capacitor must consist of a localized top side plane that connects to the PGND exposed pad
(EP).
2. Have a single point ground.
The ground connections for the feedback, soft-start, and enable components must be routed to the AGND
pin of the device. This prevents any switched or load currents from flowing in the analog ground traces. If not
properly handled, poor grounding can result in degraded load regulation or erratic output voltage ripple
behavior. Additionally provide a single point ground connection from pin 4 (AGND) to EP/PGND.
3. Minimize trace length to the FB pin.
Both feedback resistors, RFBT and RFBB must be located close to the FB pin. Since the FB node is high
impedance, maintain the copper area as small as possible. The traces from RFBT, RFBB must be routed away
from the body of the LMZ12008 to minimize possible noise pickup.
4. Make input and output bus connections as wide as possible.
This reduces any voltage drops on the input or output of the converter and maximizes efficiency. To optimize
voltage accuracy at the load, ensure that a separate feedback voltage sense trace is made to the load. Doing
so will correct for voltage drops and provide optimum output accuracy.
5. Provide adequate device heat-sinking.
Use an array of heat-sinking vias to connect the exposed pad to the ground plane on the bottom PCB layer.
If the PCB has multiple copper layers, these thermal vias can also be connected to inner layer heat-
spreading ground planes. For best results use a 10 × 10 via array or larger with a minimum via diameter of 8
mil thermal vias spaced 46.8 mil (1.5 mm). Ensure enough copper area is used for heat-sinking to keep the
junction temperature below 125°C.
VIN
AGND
AGND
EN
AGND
VIN
1 2 3 4 5 6 7
Top View
VIN
COUT
VOUT
CSS
GND
Thermal Vias
FB
CIN
GND
CFF
RFBT
RFBB
GND Plane
EPAD
NC
SS
VOUT
8 9 10 11
VOUT
Enable >
Connect EN on middle or
bottom layer
VIN
PGND
VIN VOUT
CIN COUT
Loop 1 Loop 2
VOUT
High
di/dt
24
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
10.2 Layout Examples
Figure 53. Critical Current Loops to Minimize
Figure 54. PCB Layout Guide
25
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
Layout Examples (continued)
Figure 55. Top View of Evaluation PCB
Figure 56. Bottom View of Evaluation PCB
TJA <TJ-MAX - TA-MAX
PIC_LOSS
TJA <(125 - 50) °C
3.9 W < 19.23°C
W
500
TCA
Board Area_cm2 8°C x cm2
W
.
TCA <125°C - 50°C
3.9 W - 1.0°C
W< 18.23°C
W
TCA <TJ-MAX ± TA-MAX
PIC_LOSS - TJC
26
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
10.3 Power Dissipation and Thermal Considerations
When calculating module dissipation use the maximum input voltage and the average output current for the
application. Many common operating conditions are provided in the characteristic curves such that less common
applications can be derived through interpolation. In all designs, the junction temperature must be kept below the
rated maximum of 125°C.
For the design case of VIN = 12 V, VOUT = 3.3 V, IOUT = 8 A, and TA-MAX = 50°C, the module must see a thermal
resistance from case to ambient (θCA) of less than:
(15)
Given the typical thermal resistance from junction to case (θJC) to be 1.0°C/W. Use the 85°C power dissipation
curves in the Typical Characteristics section to estimate the PIC-LOSS for the application being designed. In this
application it is 3.9 W.
(16)
To reach θCA = 18.23, the PCB is required to dissipate heat effectively. With no airflow and no external heat-sink,
a good estimate of the required board area covered by 2-oz. copper on both the top and bottom metal layers is:
(17)
As a result, approximately 27.42 square cm of 2-oz. copper on top and bottom layers is the minimum required
area for the example PCB design. This is 5.23 × 5.23 cm (2.06 × 2.06 in) square. The PCB copper heat sink
must be connected to the exposed pad. For best performance, use approximately 100, 8 mil thermal vias spaced
59 mil (1.5 mm) apart connect the top copper to the bottom copper.
Another way to estimate the temperature rise of a design is using θJA. An estimate of θJA for varying heat sinking
copper areas and airflows can be found in the typical applications curves. If our design required the same
operating conditions as before but had 225 LFPM of airflow. We locate the required θJA of
(18)
On the θRA vs copper heatsinking curve, the copper area required for this application is now only 1 square
inches. The airflow reduced the required heat sinking area by a factor of four.
To reduce the heat sinking copper area further, this package is compatable with D3-PAK surface mount heat
sinks.
For an example of a high thermal performance PCB layout for SIMPLE SWITCHER power modules, refer to AN-
2093 SNVA460, AN-2084 SNVA456, AN-2125 SNVA473, AN-2020 SNVA422 and AN-2026 SNVA424.
10.4 Power Module SMT Guidelines
The recommendations below are for a standard module surface mount assembly
• Land Pattern — Follow the PCB land pattern with either soldermask defined or non-soldermask defined pads
• Stencil Aperture
– For the exposed die attach pad (DAP), adjust the stencil for approximately 80% coverage of the PCB land
pattern
– For all other I/O pads use a 1:1 ratio between the aperture and the land pattern recommendation
• Solder Paste — Use a standard SAC Alloy such as SAC 305, type 3 or higher
• Stencil Thickness — 0.125 to 0.15 mm
• Reflow — Refer to solder paste supplier recommendation and optimized per board size and density
• Refer to Design Summary LMZ1xxx and LMZ2xxx Power Modules Family (SNAA214) for reflow information
27
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
Power Module SMT Guidelines (continued)
• Maximum number of reflows allowed is one
Figure 57. Sample Reflow Profile
Table 2. Sample Reflow Profile Table
PROBE MAX TEMP
(°C) REACHED
MAX TEMP TIME ABOVE
235°C REACHED
235°C TIME ABOVE
245°C REACHED
245°C TIME ABOVE
260°C REACHED
260°C
1242.5 6.58 0.49 6.39 0.00 – 0.00 –
2242.5 7.10 0.55 6.31 0.00 7.10 0.00 –
3241.0 7.09 0.42 6.44 0.00 – 0.00 –
28
LMZ12008
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
www.ti.com
Product Folder Links: LMZ12008
Submit Documentation Feedback Copyright © 2011–2016, Texas Instruments Incorporated
11 Device and Documentation Support
11.1 Device Support
11.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
11.1.2 Development Support
For developmental support, see the following:
WEBENCH Tool, http://www.ti.com/webench
11.2 Documentation Support
11.2.1 Related Documentation
For related documentation, see the following:
• AN-2027 Inverting Application for the LMZ14203 SIMPLE SWITCHER Power Module, (SNVA425)
•Absolute Maximum Ratings for Soldering, (SNOA549)
• AN-2024 LMZ1420x / LMZ1200x Evaluation Board (SNVA422)
• AN-2085 LMZ23605/03, LMZ22005/03 Evaluation Board (SNVA457)
• AN-2054 Evaluation Board for LM10000 - PowerWise AVS System Controller (SNVA437)
• AN-2020 Thermal Design By Insight, Not Hindsight (SNVA419)
• AN-2093 LMZ23610/8/6 and LMZ22010/8/6 Current Sharing Evaluation Board (SNVA460)
• AN-2026 Effect of PCB Design on Thermal Performance of SIMPLE SWITCHER Power Modules (SNVA424)
•Design Summary LMZ1xxx and LMZ2xxx Power Modules Family (SNAA214)
11.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.4 Trademarks
E2E is a trademark of Texas Instruments.
WEBENCH, SIMPLE SWITCHER are registered trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
11.5 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.6 Glossary
SLYZ022 —TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
29
LMZ12008
www.ti.com
SNVS716H –MARCH 2011–REVISED FEBRUARY 2016
Product Folder Links: LMZ12008
Submit Documentation FeedbackCopyright © 2011–2016, Texas Instruments Incorporated
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
PACKAGE OPTION ADDENDUM
www.ti.com 6-Feb-2020
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LMZ12008TZ/NOPB ACTIVE PFM NDY 11 32 RoHS & Green SN Level-3-245C-168 HR -40 to 85 LMZ12008
LMZ12008TZE/NOPB ACTIVE PFM NDY 11 250 RoHS & Green SN Level-3-245C-168 HR -40 to 85 LMZ12008
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LMZ12008TZE/NOPB PFM NDY 11 250 330.0 32.4 15.45 18.34 6.2 20.0 32.0 Q2
PACKAGE MATERIALS INFORMATION
www.ti.com 27-May-2018
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LMZ12008TZE/NOPB PFM NDY 11 250 367.0 367.0 55.0
PACKAGE MATERIALS INFORMATION
www.ti.com 27-May-2018
Pack Materials-Page 2
MECHANICAL DATA
NDY0011A
www.ti.com
TZA11A (Rev F)
TOP SIDE OF PACKAGE
BOTTOM SIDE OF PACKAGE
IMPORTANT NOTICE AND DISCLAIMER
TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE
DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”
AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY
IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD
PARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate
TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable
standards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants you
permission to use these resources only for development of an application that uses the TI products described in the resource. Other
reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third
party intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims,
damages, costs, losses, and liabilities arising out of your use of these resources.
TI’s products are provided subject to TI’s Terms of Sale (www.ti.com/legal/termsofsale.html) or other applicable terms available either on
ti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable
warranties or warranty disclaimers for TI products.
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2020, Texas Instruments Incorporated