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VPOL5A-12-SMT
Content
1. INTRODUCTION
2. MODELS
3. VPOL5A-12-SMT CONVERTER FEATURES
4. GENERAL DESCRIPTION
4.1 Electrical Description
4.2 Thermal Packaging and Physical Design.
5. MAIN FEATURES AND FUNCTIONS
5.1 Operating Temperature Range
5.2 Over-Temperature Protection (OTP)
5.3 Output Voltage Adjustment
5.4 Safe Operating Area (SOA)
5.5 Over Current Protection
5.6 Remote ON/OFF
5.7 UVLO (Under-Voltage Lockout)
6. SAFETY
6.1 Input Fusing and Safety Considerations.
7. APPLICATIONS
7.1 Layout Design Challenges.
7.2 Convection Requirements for Cooling
7.3 Thermal Considerations
7.4 Power De-Rating Curves
7.5 Efficiency vs Load Curves
7.6 Input Capacitance at the Power Module
7.7 Test Set-Up
7.8 VPOL5A-12-SMT
Output Voltage Adustment.
7.9 Output Ripple and Noise Measurement
7.10 Output Capacitance
7.11 VPOL5-12-SMT Reflow Profile
8. MECHANICAL OUTLINE DIAGRAMS
8.1 VPOL5A-12-SMT Mechanical Outline Diagrams
8.2 VPOL5A-12-SMT Tape and Reel Dimensions
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1. Introduction
This application note describes the features and functions of
VPOL5A-12-SMTof Non Isolated DC-DC Converters. These are
highly efficient, reliable and compact, high power density, single output
DC/DC converters. These “Point of Load” modules serve the needs
specifically of the fixed and mobile telecommunications and computing
market, employing economical distributed Power Architectures. The
VPOL5A-12-SMT provide precisely regulated output voltage range
from 0.75V to 5.0Vdc over a wide range of input voltage (Vi=8.3 –
14Vdc) and can operate over an ambient temperature range of –40℃ to
+85℃. Ultra-high efficiency operation is achieved through the use of
synchronous rectification and drive control techniques.
The modules are fully protected against short circuit and over-
temperature conditions. The world class automated manufacturing
methods, together with an extensive testing and qualification program,
ensure that all VPOL5A-12-SMT converter s are extremely reliable.
2. Models
The adjustable VPOL5A-12-SMT series models are shown in table1.
Model Input
Voltage Output
Voltage Output
Current
8.3 – 14VDC
0.75 – 5.0VDC 5A
Tabl e 1 VPOL5A-12-SMT Models
The VPOL5A-12-SMT efficiency and input current at 12Vin are
shown in table2.
Input Current (mA)
Output
Voltage Output
Current No Load Full Load Efficiency
typ.
0.75V 5A 20 428mA 73%
1.2V 5A 25 625mA 80%
1.5V 5A 25 762mA 82%
1.8V 5A 30 893mA 84%
2.0V 5A 30 980mA 85%
2.5V 5A 35 1197mA 87%
3.3V 5A 45 1545mA 89%
5.0V 5A 50 2264mA 92%
Table 2 – VPOL5A-12-SMT Efficiency and Input Current
3. VPOL5A-12-SMT Converter Features
High efficiency topology, typically 89% at 3.3Vdc
Industry standard footprint
Wide ambient temperature range, -40C to +85C
Cost efficient open frame design
Programmable output voltage via external resistor from 0.75 to
5.0Vdc
No minimum load requirement (Stable at all loads)
Remote ON/OFF
Fixed switching frequency
Continuous short-circuit protection and over current protection
Over-temperature protection (OTP)
Monotonic Startup with pre-bias at the output.
UL/IEC/EN60950 Certified.
4. General Description
4.1 Electrical Description
A block diagram of the VPOL5A-12-SMT converter is shown in
Figure 1. Extremely high efficiency power conversion is achieved
through the use of synchronous rectification and drive techniques.
Essentially, the powerful VPOL5A-12-SMT topology is based on a
non-isolated synchronous buck converter. The control loop is optimized
for unconditional stability, fast transient response and a very tight line
and load regulation. In a typical pre-bias application the VPOL5-12- SMT
converters do not draw any reverse current at start-up. The
output voltage can be adjusted from 0.75 to 5.0vdc, using the TRIM pin
with a external resistor. The converter c an be shut down via a remote
ON/OFF input that is referenced to ground. This input is compatible with
popular logic devices; a 'positive' logic input is supplied as standard.
Positive logic implies that the converter is enabled if the remote
ON/OFF input is high (or floating), and disabled if it is low. The
converter is also protected against over-temperature conditions. If the
converter is overloaded or the ambient temperature gets too high, the
converter will shut down to protect the unit.
C1 C2
Q2
Q1
D1
L1
+VIN
COM COM
+VO
PWM IC R1
R2
R trim
ERR AMP
ON/OFF TRIM
Figure 1. Electrical Block Diagram
VPOL5A-12-SMT
VPOL5A-12-SMT
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4.2 Thermal Packaging and Physical Design.
The VPOL5A-12-SMT uses a multi-layer FR4 PCB construction. All
surface mount power components are placed on one side of the PCB,
and all low-power control components are placed on the other side.
Thus, the Heat dissipation of the power components is optimized,
ensuring that control components are not thermally stressed. The
converter is an open-frame product and has no case or case pin. The
open-frame design has several advantages over encapsulated closed
devices. Among these advantages are:
Efficient Thermal Management: the heat is removed from the
heat generating components without heating more sensitive, small
signal control components.
Environmental: Lead free open-frame converters are more easily
re-cycled.
Cost Efficient: No encapsulation. Cost efficient open-frame
construction.
Reliable: Efficient cooling provided by open frame construction
offers high reliability and easy diagnostics.
5. Main Features and Functions
5.1 Operating Temperature Range
VPOL5A-12-SMT converters highly efficient converter
design has resulted in its ability to operate over a wide ambient
temperature environment ( -40℃ to 85℃). Due consideration must be
given to the de-rating curves when ascertaining maximum power that
can be drawn from the converter. The maximum power drawn is
influenced by a number of factors, such as:
Input voltage range.
Output load current.
Air velocity (forced or natural convection).
Mounting orientation of converter PCB with respect to the Airflow.
Motherboard PCB design, especially ground and power planes.
These can be effective heat sinks for the converter.
5.2 Over-Temperature Protection (OTP)
The VPOL5A-12-SMT converters are equipped with non-latching
over-temperature protection. A temperature sensor monitors the
temperature of the hot spot (typically, top switch). If the temperature
exceeds a threshold of 120°C (typical) the converter will shut down,
disabling the output. When the temperature has decreased the
converter will automatically restart.
The over-temperature condition can be induced by a variety of reasons
such as external overload condition or a system fan failure.
5.3 Output Voltage Adjustment
Section 7.8 describes in detail as to how to trim the output voltage with
respect to its set point. The output voltage on all models is trimmable in
the range 0.75 – 5.0Vdc.
5.4 Safe Operating Area (SOA)
Figure 2 provides a graphical representation of the Safe Operating Area
(SOA) of the converter. This representation assumes ambient
operating conditions such as airflow are met as per thermal guidelines
provided in Sections 7.2 and 7.3.
Vo
IoIo,CLIo,max
Vo,nom
Safe Operating Area
CURRENT (A)
VOLTAGE (V)
Figure 2. Maximum Output Current Safe Operating Area
5.5 Over Current Protection
All different voltage models have a full continuous short-circuit
protection. The unit will auto recover once the short circuit is removed.
To provide protection in a fault condition, the unit is equipped with
internal over-current protection. The unit operates normally once the
fault condition is removed. The power module will supply up to 150% of
rated current. In the event of an over current converter will go into a
hiccup mode protection.
5.6 Remote ON/OFF
The remote ON/OFF input feature of the converter allows external
circuitry to turn the converter ON or OFF. Active-high remote ON/OFF
is available as standard. The VPOL5A-12-SMT converters are
turned on if the remote ON/OFF pin is high, or left open or floating.
Setting the pin low will turn the converter ‘Off’. The signal level of the
remote on/off input is defined with respect to ground. If not using the
remote on/off pin, leave the pin open (module will be on). The part
number suffix “N” is Negative remote ON/OFF version. The unit is
guaranteed OFF over the full temperature range if this voltage level
exceeds 2.8Vdc. The converters are turned on If the on/off pin input is
low or left open. The recommended VPOL5A-12-SMT remote on/off drive
curcuitas shown as figure 3, 4.
VPOL5A-12-SMT
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Q1 VPOL5A-12-SMT
ON/OFF
Control
+Vin +Vo
Remote ON/OFF
CommonCommon
Figure 3. Positive Remote ON/OFF Input Drive Circuit
Q1
ON/OFF
Control
+Vin
Remote ON/OFF
Common Common
+Vo
VPOL5A-12-SMT
Figure 4. Negative Remote ON/OFF Input Drive Circuit
5.7 UVLO (Under-Voltage Lockout)
The voltage on the Vcc pin determines the start of the operation of the
Converter. When the input Vcc rises and exceeds about 8.0V the
converter initiates a soft start. The UVLO function in the converter has a
hysteresis (about 100mV) built in to provide noise immunity at s tart-up.
6. Safety
6.1 Input Fusing and Safety Considerations.
Agency Approvals: The power Supply shall be submitted to and
receive formal approval from the following test agencies.
1.The power supply shall be approved by a nationally recognized
testing laboratory to UL/CSA 60950 3rd Edition (North America) and
EN60950 (International)
2. CB Certificate from an internationally recognized test house in
accordance with EN 60950.
The VPOL5A-12-SMT converters do not have an internal fuse.
However, to achieve maximum safety and system protection, always
use an input line fuse. The safety agencies require a time-delay fuse
with a maximum rating of 7A.
7. Applications
7.1 Layout Design Challenges.
In optimizing thermal design the PCB is utilized as a heat sink. Also
some heat is transferred from the VPOL5A-12-SMT module to the main
board through connecting pins. The system designer or the end user must
ensure that other components and metal in the vicinity of the
VPOL5A-12-SMT meet the spacing requirements to which the
system is approved.
Low resistance and low inductance PCB layout traces are the norm and
should be used where possible. Due consideration must also be given
to proper low impedance tracks between power module, input and
output grounds. The recommended VPOL5A-12-SMT foot print as shown
as figure 6.
PAD SIZE
MIN : 0.120" x 0.095 "
MAX : 0.135" x 0.110 "
Dimensions are in Inches ( millimetes )
Recommended Pad Layout
0.340
0.180 0.160 0.160 0.190
0.350
0.690
0.05
VOUT TRIM GND
VIN
ON/OFF
(4.57) (4.06) (4.06) (4.83)
0.06
(1.5) (1.3) (17.53)
(8.89)
0.010
(0.25)
(8.64)
Figure 6. Recommended VPOL5A-12-SMT Footprint (Top View)
VPOL5A-12-SMT
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7.2 Convection Requirements for Cooling
To predict the approximate cooling needed for the module, refer to the
Power De-rating curves in Figures 10 to 13 . These de-rating curves are
approximations of the ambient temperatures and airflows required to
keep the power module temperature below its maximum rating. Once
the module is assembled in the actual system, the module’s
temperature should be checked as shown in Figure 7 to ensure it does
not exceed 110°C.
Proper cooling can be verified by measuring the power module’s
temperature at Q1-pin 6 as shown in Figure 8,9.
25.4(1.0)
12.7(0.5)
76.2(3.0)
Power Module
A
ir
flow
Therm oc u ple L ocation
for me asu rin g
am bient tem p eratu re
and airflow
Bakelite
Wind
Tunnel
Note : Dimensions are in millimeters and (inches)
Figure 7. Thermal Test Setup
Figure 9. Temperature Measurement Location for VPOL5A-12-SMT
7.3 Thermal Considerations
The power module operates in a variety of thermal environments;
however, sufficient cooling should be provided to help ensure reliable
operation of the unit. Heat is removed by conduction, convection, and
radiation to the surrounding environment. The thermal data presented is
based on measurements taken in a set-up as shown in Figure7.
Figures 10 to 13 represent the test data. Note that the airflow is parallel
to the long axis of the module as shown in Figure7 for the VPOL5A-12-SMT..
The temperature at either location should not exceed 110 °C. The
output power of the module should not exceed the rated power for the
module (VO, set x IO, max). The VPOL5A-12-SMT thermal data presented
i
based on measurements taken in a wind tunnel. The test setup shown
in Figure 7 and EUT need to solder on 33mm x 40.38mm(1.300'' x
1.59'') test pcb. Note that airflow is parallel to the long axis of the
module as shown in Fig7.
VPOL5A-12-SMT
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VPOL5A-12-SMT (Vo=5.0V) Derating Curve
0.00
1.00
2.00
3.00
4.00
5.00
6.00
20 30 40 50 60 70 80 90 100
Ambient Temperature(oC)
Output Current(A)
0LFM
100LFM
200LFM
0.00
1.00
2.00
3.00
4.00
5.00
6.00
20 30 40 50 60 70 80 90 100
Am bi ent Temperature(oC)
Output Current(A)
0LFM
100LFM
200LFM
Figure12a.Typical Power De-rating for 12V IN 5.0Vout Figure12b.Typical Power De-rating for 12V IN 3.3Vout
0.00
1.00
2.00
3.00
4.00
5.00
6.00
20 30 40 50 60 70 80 90 100
Ambient Temperature(oC)
Output Current(A)
0LFM
100LFM
200LFM
0.00
1.00
2.00
3.00
4.00
5.00
6.00
20 30 40 50 60 70 80 90 100
Ambient Temp erature(oC)
Output Current(A)
0LFM
100LFM
200LFM
Figure12c.Typical Power De-rating for 12V IN 2.5Vout Figure 12d.Typical Power De-rating for 12V IN 2.0Vout
0.00
1.00
2.00
3.00
4.00
5.00
6.00
20 30 40 50 60 70 80 90 100
Ambient Temperature(oC)
Output Current(A)
0LFM
100LFM
200LFM
0.00
1.00
2.00
3.00
4.00
5.00
6.00
20 30 40 50 60 70 80 90 100
Ambient Temperature(oC)
Output Current(A)
0LFM
100LFM
200LFM
Figure12e.Typical Power De-rating for 12V IN 1.8Vout Figure 12f.Typical Power De-rating for 12V IN 1.5Vout
VPOL5A-12-SMT (Vo=3.3V) Derating Curve
VPOL5A-12-SMT (Vo=2.5V) Derating Curve VPOL5A-12-SMT (Vo=2.0V) Derating Curve
VPOL5A-12-SMT (Vo=1.8V) Derating Curve VPOL5A-12-SMT (Vo=1.5V) Derating Curve
VPOL5A-12-SMT
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0.00
1.00
2.00
3.00
4.00
5.00
6.00
20 30 40 50 60 70 80 90 100
Ambient Temperature(oC)
Output Current(A)
0LFM
100LFM
200LFM
0.00
1.00
2.00
3.00
4.00
5.00
6.00
20 30 40 50 60 70 80 90 100
Ambient Temperature(oC)
Output Current(A)
0LFM
100LFM
200LFM
Figure13a.Typical Power De-rating for 12V IN 1.2Vout Figure 13b.Typical Power De-rating for 12V IN 0.75Vout
(Vo=1.2V) Derating Curve
VPOL5A-12-SMT (Vo=0.75 V) Derating Curve
VPOL5A-12-SMT
VPOL5A-12-SMT
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VPOL5A-12-SMTVo=1.8V (Eff Vs Io)
70%
75%
80%
85%
90%
95%
100%
00.511.522.533.544.55
Current Load (A)
Efficincy (%)
8.3V
12V
14V
60%
65%
70%
75%
80%
85%
90%
95%
100%
00.511.522.533.544.55
Current Load (A)
Efficincy (%)
8.3V
12V
14V
60%
65%
70%
75%
80%
85%
90%
95%
100%
00.511.522.533.544.55
Current Load (A)
Efficincy (%)
8.3V
12V
14V
50%
55%
60%
65%
70%
75%
80%
85%
90%
00.511.522.533.544.55
Current Load (A)
Efficincy (%)
8.3V
12V
14V
VPOL5A-12-SMTVo=1.5V (Eff Vs Io)
VPOL5A-12-SMTVo=1.2V (Eff Vs Io) VPOL5A-12-SMTVo=0.75V (Eff Vs Io)
VPOL5A-12-SMT
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7.6 Input Capacitance at the Power Module
The VPOL5A-12-SMT converters must be connected to a low AC source
impedance. To avoid problems with loop stability source inductance
should be low. Also, the input capacitors should be placed close to the
converter input pins to de-couple distribution inductance. However, the
external input capacitors are chosen for suitable ripple handling
capability. Low ESR polymers are a good choice. They have high
capacitance, high ripple rating and low ESR (typical <100mohm).
Electrolytic capacitors should be avoided. Circuit as shown in Figure 14
represents typical measurement methods for ripple current. Input
reflected-ripple current is measured with a simulated source Inductance
of 1uH. Current is measured at the input of the module.
+Vin
Common
VPOL5A-12-SMT
220uF
ESR<0.1ohm
2*100uF
Tantalum
L1
1uH
+Power
Supply
To Oscilloscope
Figure 14. Input Reflected-Ripple Test Setup
7.7 Test Set-Up
The basic test set-up to measure parameters such as efficiency and
load regulation is shown in Figure 15. Things to note are that this
converter is non-isolated, as such the input and output share a common
ground. These grounds should be connected together via low
impedance ground plane in the application circuit. When testing a
converter on a bench set-up, ensure that -Vin and -Vo are connected
together via a low impedance short to ensure proper efficiency and load
regulation measurements are being made. When testing the
VPOL5A-12-SMT under any transient conditions please ensure that
the transient response of the source is sufficient to power the
equipment under test. We can calculate the
Efficiency
Load regulation and line regulation.
The value of efficiency is defined as:
%100
IinVin IoVo
Where: Vo is output voltage,
Io is output current,
Vin is input voltage,
Iin is input current.
The value of load regulation is defined as:
%100. NL
NLFL
VVV
regLoad
Where: VFL is the output voltage at full load
VNL is the output voltage at no load
The value of line regulation is defined as:
%100. LL
LLHL
VVV
regLine
Where: VHL is the output voltage of maximum input voltage at full load.
VLL is the output voltage of minimum input voltage at full load.
+Vin
Common
VPOL5A-12-SMT
47uF
+
Power
Supply
A
V
Current Meter
Voltage Meter
+Vo
Common
+Sense
Load
V
A
10UF
CERAMIC
Figure 15. VPOL5A-12-SMT Test Setup
VPOL5A-12-SMT
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7.8 VPOL5A-12-SMT Output Voltage Adustment.
The output Voltage of the VPOL5A-12-SMT can be adjusted in the
range 0.75V to 5.0V by connecting a single resistor on the motherboard
(shown as R trim) in Figure 17. When Trim resistor is not connected the
output voltage defaults to 0.75V
+Vin
Common Common
+Vo
VPOL5-12-SMT R trim-up
R-Load
Trim
Figure 17. Trim-up Voltage Setup
The value of Rtrim-up defined as:
Where: Rtrim-up is the external resistor in ohm,
Vo is the desired output voltage
To give an example of the above calculation, to set a voltage of 3.3Vdc,
Rtrim is given by:
Rtrim = 3118 ohm
For various output values various resistors are calculated and provided
in Table 3 for convenience.
Vo,set (V) Rtrim (Kohm)
0.75 Open
1.2 22.33
1.5 13.00
1.8 9.00
2.0 7.40
2.5 5.00
3.3 3.12
5.0 1.47
Table 3 – Trim Resistor Values
7.9 Output Ripple and Noise Measurement
The test set-up for noise and ripple measurements is shown in Figure
18. a coaxial cable with a 50ohm termination was used to prevent
impedance mismatch reflections disturbing the noise readings at higher
frequencies.
Figure 18. Output Voltage Ripple and Noise Measurement Set-Up
7.10 Output Capacitance
VPOL5A-12-SMTconverters provide unconditional stability
with or without external capacitors. For good transient response low
ESR output capacitors should be located close to the point of load.
For high current applications point has already been made in layout
considerations for low resistance and low inductance tracks.
Output capacitors with its associated ESR values have an impact on
loop stability and bandwidth. The converters are designed to work
with load capacitance up-to 3,000uF. It is recommended that any
additional capacitance, Maximum 3,000uF and low ESR, be connected
close to the point of load and outside the remote compensation point.
7.11 VPOL5A-12-SMT Reflow Profile
An example of the VPOL5A-12-SMT reflow profile is given in Figure 19.
Equipment used: SMD HOT AIR REFLOW HD-350SAR
Alloy: AMQ-M293TA or NC-SMQ92 IND-82088 SN63
REFLOW PROFILE
0
40
80
120
160
200
240
0 30 60 90 120 150 180 210 240
TIME (SECONDS)
TEMPERATURE (C
)
Figure 19 VPOL5A-12-SMT Reflow Profile
)1000
75.0
10500
(Vo
Rtrim
)1000
75.03.310500
(Rtrim
+Vin
Common Common
+Vo
VPOL5A-12-SMT R-Load
10uF
Tant. 1uF
Ceramic Test Jack
VPOL5A-12-SMT
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8. Mechanical Outline Diagrams
8.1 VPOL5A-12-SMT Mechanical Outline Diagrams
Dimensions are in millimeters and inches
Tolerance: x.xx ±0.02 in. (0.5mm) , x.xxx ±0.010 in. (0.25 mm) unless
otherwise noted
Dimensions are in Inches (millimeters)
Tolerances :x.xx ± 0.02in.( x.x ± 0.5mm) , unless otherwise noted
BOTTOM VIEW OF BOARD
0.80
0.340
0.450
0.05
0.180
0.35
0.062 0.090
0.1600.160
0.190 0.065
0.24
x.xxx ± 0.010in. ( x.xx ± 0.25mm)
Surface Mount Contact 5 Places
GND TRIM VOUT
ON/OFF
VIN
(4.83) (4.06) (4.06) (4.06)
(20.3)
(2.29)
(1.57)
(8.9) (8.64)
(11.43)
(1.5)
(1.3)
0.06
(1.65)
(6.09) max.
Figure 21 VPOL5A-12-SMT Mechanical Outline Diagram
8.2 VPOL5A-12-SMT Tape and Reel Dimensions
The Tape Reel dimensions for the VPOL5A-12-SMT
module is shown in Figure 22.
t
E
Po
t
P2
D
D1
P
F
Ko
Ao
Bo
W
Figure 22 – VPOL5A-12-SMT Tape and Reel Dimensions
VPOL5A-12-SMT
