LP2951CMX-3.0 - National Semiconductor

LP2950*/2951

100mA Low-Dropout Voltage Regulator

* LP2950 Discontinuance September 2007.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

September 2008 M9999-091208

General Description

The LP2950 and LP2951 are micropower voltage

regulators with very low dropout voltage (typically 40mV at

light loads and 380mV at 100mA), and very low quiescent

current (75A typical). The quiescent current of the LP2950

/LP2951 increases only slightly in dropout, thus prolonging

battery life. This feature, among others, makes the LP2950

and LP2951 ideally suited for use in battery-powered

systems.

Available in a 3-pin TO-92 package, the LP2950 is pin-

compatible with the older 5V regulators. Additional system

functions, such as programmable output voltage and logic-

controlled shutdown, are available in the 8-pin DIP and 8-

pin SOIC versions of the LP2951.

Data sheets and support documentation can be found on

Micrel’s web site at: www.micrel.com.

Features

• High accuracy 5V, guaranteed 100mA output

• Extremely low quiescent current

• Low-dropout voltage

• Extremely tight load and line regulation

• Very low temperature coefficient

• Use as regulator or reference

• Needs only 1µF for stability

LP2951 Versions Only

• Current and thermal limiting

• Error flag warns of output dropout

• Logic-controlled electronic shutdown

• Output programmable from 1.24 to 29V

Applications

• Automotive electronics

• Voltage reference

• Avionics

___________________________________________________________________________________________________________

Block Diagram

LP2590 and LP295 1 Block Diagram

(Pin Numbers Refer to LP2591)

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Additional features available with the LP2951 also

include an error flag output that warns of a low output

voltage, which is often due to failing batteries on the

input. This may also be used as a power-on reset. A

logic-compatible shutdown input is also available which

enables the regulator to be switched on and off. This

part may also be pin-strapped for a 5V output, or

programmed from 1.24V to 29V with the use of two

external resistors.

The LP2950 is available as either a -02 or -03 version.

The -02 and -03 versions are guaranteed for junction

temperatures from –40°C to +125°C; the -02 version has

a tighter output and reference voltage specification

range over temperature. The LP2951 is available as an

-02 or -03 version.

The LP2950 and LP2951 have a tight initial tolerance

(0.5% typical), a very low output voltage temperature

coefficient which allows use as a low-power voltage

reference, and extremely good load and line regulation

(0.05% typical). This greatly reduces the error in the

overall circuit, and is the result of careful design

techniques and process control.

___________________________________________________________________________________________________________

Ordering Information

Part Number Voltage Accuracy Junction

Temperature Range Package Lead Finish

LP2950-02BZ* 5.0V 0.5% –40° to +125°C 3-Pin TO-92 Plastic Standard

LP2950-03BZ* 5.0V 1.0% –40° to +125°C 3-Pin TO-92 Plastic Standard

LP2951-02BM 5.0V 0.5% –40° to +125°C 8-Pin SOIC Standard

LP2951-03BM 5.0V 1.0% –40° to +125°C 8-Pin SOIC Standard

LP2951-02BN 5.0V 0.5% –40° to +125°C 8-Pin Plastic DIP Standard

LP2951-03BN** 5.0V 1.0% –40° to +125°C 8-Pin Plastic DIP Standard

LP2951-02YM 5.0V 0.5% –40° to +125°C 8-Pin SOIC Pb-Free

LP2951-03YM 5.0V 1.0% –40° to +125°C 8-Pin SOIC Pb-Free

LP2951-02YN 5.0V 0.5% –40° to +125°C 8-Pin Plastic DIP Pb-Free

Note:

* TO-92 Package discontinuance notification issued September 2007. End-of-life-buy offer thru December 31, 2007. Contact factory for

additional information.

** Contact factory for Pb-Free version.

Pin Configur ation

TO-92 (Z)

(Bottom View) DIP (N) and SOIC (M)

See MIC2950 for a part with: 1) higher output (150 mA), 2) transient protection (60V), an d 3) reverse input protection to –20V.

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Absolute Maximum Ratings(1)

If Military/Aerospace specified devices are required,

contact your local Micrel representative/distributor for

availability and specifications.

Power Dissipation .....................................Internally Limited

Lead Temperature (soldering, 5 sec.)........................ 260°C

Storage Temperature ................................–65°C to +150°C

Operating Junction Temperature Range(8)

LP2950, LP2951.................................–40°C to +125°C

Input Supply Voltage ........................................–0.3 to +30V

Feedback Input Voltage(9, 10) ............................–1.5 to +30V

Shutdown Input Voltage(9) ................................–0.3 to +30V

Error Comparator Output Voltage(9) .................–0.3 to +30V

ESD Rating is to be determined

Electrical Characteristics(1)

TA = 25°C except as noted.

Parameter Condition Min Typ Max Units

LP295x-02 (±0.5%) 4.975 5.000 5.025 V

LP295x-03 (±1%) 4.950 5.000 5.050 V

Output Voltage

TJ = 25°C

LP2951-4.8 (±1%) 4.802 4.850 4.899 V

LP295x-02 (±0.5%) 4.950 5.050 V

LP295x-03 (±1%) 4.925 5.075 V

Output Voltage

–25°C ≤ TJ ≤ +85°C

LP2951-4.8 (±1%) 4.777 4.872 V

LP295x-02 (±0.5%) 4.940 5.060 V

LP295x-03 (±1%) 4.900 5.100 V

Output Voltage

Over Full Temperature Range

–40°C to +125°C

LP2951-4.8 (±1%) 4.753 4.947 V

LP295x-02 (±0.5%), 100µA ≤ IL ≤ 100mA, TJ ≤ TJ(max) 4.930 5.070 V

LP295x-03 (±1%), 100µA ≤ IL ≤ 100mA, TJ ≤ TJ(max) 4.880 5.120 V

Output Voltage

Over Load Variation

LP2951-4.8 (±1%), 100µA ≤ IL ≤ 100mA, TJ ≤ TJ(max) 4.733 4.967 V

LP295x-02 (±0.5%), Note 12 20 100

ppm/°C

LP295x-03 (±1%), Note 12 50 150

ppm/°C

Output Voltage

Temperature Coefficient

LP2951-4.8 (±1%), Note 12 50 150

ppm/°C

LP295x-02 (±0.5%), Notes 14 , 15 0.03

0.10

0.20

LP295x-03 (±1%), Notes 14, 15 0.04

0.20

0.40

Line Regulation

LP2951-4.8 (±1%), Notes 14, 15 0.04

0.20

0.40

LP295x-02 (±0.5%), Note 14, 100µA ≤ IL ≤ 100mA 0.04

0.10

0.20

LP295x-03 (±1%), Note 14, 100µA ≤ IL ≤ 100mA 0.10

0.20

0.30

Load Regulation

LP2951-4.8 (±1%), Note 14, 100µA ≤ IL ≤ 100mA 0.10

0.20

0.30

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Parameter Condition Min Typ Max Units

Note 5, IL = 100µA 50

150

Dropout Voltage

Note 5, IL = 100mA 380

450

600

IL = 100µA 100 150

200

µA

Ground Current

IL = 100mA 8 12

Dropout Current VIN = 4.5V, IL = 100µA 180 250

310

µA

Current Limit VOUT = 0V 160 220

220

Thermal Regulation Note 13 0.05 0.20 %/W

10Hz to 100kHz, CL = 1µF 430 µVRMS

10Hz to 100kHz, CL = 200µF 160 µVRMS

Output Noise

10Hz to 100kHz, CL = 3.3µF,

0.01µF bypass Feedback to Output

100 µVRMS

LP295x-02 (±0.5%) 1.220

1.200

1.235 1.250

1.260

LP295x-03 (±1%) 1.210

1.200

1.235 1.260

1.270

Reference Voltage

LP2951-4.8 (±1%) 1.210

1.200

1.235 1.260

1.270

LP295x-02 (±0.5%), Note 7 1.190 1.270 V

LP295x-03 (±1%), Note 7 1.185 1.285 V

Reference Voltage

LP2951-4.8 (±1%), Note 7 1.185 1.285 V

Feedback Bias Current 20 40

LP295x-02 (±0.5%), Note 12 20 ppm/°C

LP295x-03 (±1%), Note 12 50 ppm/°C

Reference Voltage

LP2951-4.8 (±1%), Note 12 50 ppm/°C

Feedback Bias Current

Temperature Coefficient

0.1 nA/°C

Output Leakage Current VOH = 30V 0.01 1.00

2.00

µA

Output Low Voltage (Flag) VIN = 4.5V, IOL = 200µA 150 250

400

Upper Threshold Voltage Note 6 40

60 mV

Lower Threshold Voltage Note 6 75

140

Hysteresis Note 6 15 mV

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Parameter Condition Min Typ Max Units

LP295x-02 (±0.5%)

Low

High

2.0

1.3

0.7 V

LP295x-03 (±1%)

Low

High

2.0

1.3

0.7 V

Input Logic Voltage

LP2951-4.8 (±1%)

Low

High

2.0

1.3

0.7 V

VSHUTDOWN = 2.4V 30 50

100

µA

Shutdown Input Current

VSHUTDOWN = 30V 450 600

700

µA

Regulator Output Current

in Shutdown

Note 11 3

µA

Notes:

1. Boldface limits apply at temperature extremes.

2. Unless otherwise specified all limits guaranteed for TJ = 25°C, VIN = 6V, IL = 100µA and CL = 1µF. Additional conditions for the 8-pin versions are

Feedback tied to 5V Tap and Output tied to Output Sense (VOUT = 5V) and VSHUTDOWN ≤ 0.8V.

3. Guaranteed and 100% production tested.

4. Guaranteed but not 100% production tested. These limits are not used to calculate outgoing AQL levels.

5. Dropout voltage is defined as the input to output differential at which the output voltage drops 100mV below its nominal value measured at 1V

differential. At very low values of programmed output voltage, the minimum input supply voltage of 2V (2.3V over temperature) must be taken into

account.

6. Comparator thresholds are expressed in terms of a voltage differential at the Feedback terminal below the nominal reference voltage measured at

6V input. To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = VOUT /VREF =(R1 + R2)/R2. For

example, at a programmed output voltage of 5V, the Error output is guaranteed to go low when the output drops by 95mV x 5V/1.235V = 384mV.

Thresholds remain constant as a percent of VOUT as VOUT is varied, with the dropout warning occurring at typically 5% below nominal, 7.5%

guaranteed.

7. VREF ≤ VOUT ≤ (VIN – 1 V), 2.3V ≤ VIN ≤ 30V, 100µA < IL ≤ 100mA, TJ ≤ TJMAX.

8. The junction-to-ambient thermal resistance of the TO-92 package is 180°C/W with 0.4” leads and 160°C/W with 0.25” leads to a PC board. The

thermal resistance of the 8-pin DIP package is 105°C/W junction-to-ambient when soldered directly to a PC board. Junction-to-ambient thermal

resistance for the SOIC (M) package is 160°C/W.

9. May exceed input supply voltage.

10. When used in dual-supply systems where the output terminal sees loads returned to a negative supply, the output voltage should be diode-clamped

to ground.

11. VSHUTDOWN ≥ 2V, VIN ≤ 30 V, VOUT = 0, with Feedback pin tied to 5V Tap.

12. Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.

13. Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load or line

regulation effects. Specifications are for a 50mA load pulse at VIN = 30V (1.25W pulse) for t = 10ms.

14. Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating

effects are covered in the specification for thermal regulation.

15. Line regulation for the LP2951 is tested at 150°C for IL = 1mA. For IL = 100µA and TJ = 125°C, line regulation is guaranteed by design to 0.2%. See

Typical Performance Characteristics for line regulation versus temperature and load current.

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Typical Characteristics

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Typical Characteristics (continued)

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Typical Characteristics (continued)

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Application Information

External Capacitors

A 1.0µF (or greater) capacitor is required between the

LP2950/LP2951 output and ground to prevent

oscillations due to instability. Most types of tantalum or

aluminum electrolytics will be adequate; film types will

work, but are costly and therefore not recommended.

Many aluminum electrolytics have electrolytes that

freeze at about –30°C, so solid tantalum capacitors are

recommended for operation below –25°C. The important

parameters of the capacitor are an effective series

resistance of about 5 or less and a resonant frequency

above 500kHz. The value of this capacitor may be

increased without limit.

At lower values of output current, less output

capacitance is required for output stability. The capacitor

can be reduced to 0.33µF for current below 10mA or

0.1µF for currents below 1mA. Using the 8-pin versions

at voltages below 5V runs the error amplifier at lower

gains so that more output capacitance is needed. For

the worst-case situation of a 100mA load at 1.23V output

(Output shorted to Feedback) a 3.3µF (or greater)

capacitor should be used.

The LP2950 will remain stable and in regulation with no

load in addition to the internal voltage divider, unlike

many other voltage regulators. This is especially

important in CMOS RAM keep-alive applications. When

setting the output voltage of the LP2951 version with

external resistors, a minimum load of 1µA is recomm-

ended.

A 0.1µF capacitor should be placed from the

LP2950/LP2951 input to ground if there is more than 10

inches of wire between the input and the AC filter

capacitor or if a battery is used as the input.

Stray capacitance to the LP2951 Feedback terminal (pin

7) can cause instability. This may especially be a

problem when using high value external resistors to set

the output voltage. Adding a 100pF capacitor between

Output and Feedback and increasing the output

capacitor to at least 3.3µF will remedy this.

Error Detection Comparator Output

A logic low output will be produced by the comparator

whenever the LP2951 output falls out of regulation by

more than approximately 5%. This figure is the

comparator’s built-in offset of about 60mV divided by the

1.235V reference voltage. (Refer to the block diagram on

Page 1). This trip level remains “5% below normal”

regardless of the programmed output voltage of the

LP2951. For example, the error flag trip level is typically

4.75V for a 5V output or 11.4V for a 12V output. The out

of regulation condition may be due either to low input

voltage, current limiting, or thermal limiting.

Figure 1 is a timing diagram depicting the /ERROR

signal and the regulated output voltage as the LP2951

input is ramped up and down. The /ERROR signal

becomes valid (low) at about 1.3V input. It goes high at

about 5V input (the input voltage at which VOUT = 4.75V).

Since the LP2951’s dropout voltage is load-dependent

(see curve in Typical Performance Characteristics), the

input voltage trip point (about 5V) will vary with the load

current. The output voltage trip point (approximately

4.75V) does not vary with load.

The error comparator has an open-collector output which

requires an external pull-up resistor. Depending on

system requirements, this resistor may be returned to

the 5V output or some other supply voltage. In

determining a value for this resistor, note that while the

output is rated to sink 400µA, this sink current adds to

battery drain in a low battery condition. Suggested

values range from 100k to 1MΩ. The resistor is not

required if this output is unused.

Programming the Output Voltage (LP2951)

The LP2951 may be pin-strapped for 5V using its

internal voltage divider by tying Pin 1 (output) to Pin 2

(SENSE) and Pin 7 (FEEDBACK) to Pin 6 (5V TAP).

Alternatively, it may be programmed for any output

voltage between its 1.235V reference and its 30V

maximum rating. An external pair of resistors is required,

as shown in Figure 2.

The complete equation for the output voltage is:

2FB

REFOUT R I

1VV +

⎭

⎬

⎫

⎩

⎨

⎧+×=

where VREF is the nominal 1.235 reference voltage and

IFB is the feedback pin bias current, nominally 20nA. The

minimum recommended load current of 1µA forces an

upper limit of 1.2MΩ on the value of R2, if the regulator

must work with no load (a condition often found in

CMOS in standby), IFB will produce a 2% typical error in

VOUT which may be eliminated at room temperature by

trimming R1. For better accuracy, choosing R2 = 100kΩ

reduces this error to 0.17% while increasing the resistor

program current to 12µA. Since the LP2951 typically

draws 60µA at no load with Pin 2 open-circuited, this is a

small price to pay.

Reducing Output Noise

In reference applications it may be advantageous to

reduce the AC noise present at the output. One method

is to reduce the regulator bandwidth by increasing the

size of the output capacitor. This is the only method by

which noise can be reduced on the 3-pin LP2950 and is

relatively inefficient, as increasing the capacitor from 1µF

to 220µF only decreases the noise from 430µV to

160µVrms for a 100kHz bandwidth at 5V output.

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Noise can be reduced fourfold by a bypass capacitor

across R1, since it reduces the high frequency gain from

4 to unity. Pick:

200HzR2

BYPASS •

≅

or about 0.01µF. When doing this, the output capacitor

must be increased to 3.3µF to maintain stability. These

changes reduce the output noise from 430µV to

100µVrms for a100kHz bandwidth at 5V output. With the

bypass capacitor added, noise no longer scales with

output voltage so that improvements are more dramatic

at higher output voltages.

Figure 1. ERROR Output Timing

Figure 2. Adjustable Regulator

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Typical Applications

Wide Input Voltage Range Current Limiter 5V Regulator with 2.5V Sleep Function

Low Drift Current Source 5V Current Limiter

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Typical Applications

Regulator with Early Warning and Auxiliary Output

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Typical Applications

Latch Off When Error Flag Occurs Open Circuit Detector for 4mA to 20mA Current Loop

Regulator with State-of-Charge Indicator

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Typical Applications

Low Battery Disconnect

System Over Temperature Pro t ectio n Circuit

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Schematic Diagram

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Package Information

8-Pin SOIC (M)

0.380 (9.65)

0.370 (9.40) 0.135 (3.43)

0.125 (3.18)

PIN 1

DIMENSIONS:

INCH (MM)

0.018 (0.57)

0.100 (2.54)

0.013 (0.330)

0.010 (0.254)

0.300 (7.62)

0.255 (6.48)

0.245 (6.22)

0.380 (9.65)

0.320 (8.13)

0.0375 (0.952)

0.130 (3.30)

8-Pin Plastic DIP (N)

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10° typ.

5° typ.

0.185 (4.699)

0.175 (4.445)

0.185 (4.699)

0.175 (4.445)

0.085 (2.159) Diam.

0.500 (12.70) Min.

0.090 (2.286) typ.

0.0155 (0.3937)

0.0145 (0.3683)

Seat ing Plane

0.025 (0.635) Max

Uncontrolled

Lead Diamet er

0.016 (0.406)

0.014 (0.356)

0.105 (2.667)

0.095 (2.413)

0.055 (1.397)

0.045 (1.143)

0.090 (2.286) Radius, typ

0.145 (3.683)

0.135 (3.429)

0.055 (1.397)

0.045 (1.143)

BOTTOM VIEW

TO-92 (Z)

MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com

The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its

use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product

can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant

into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A

Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully

indemnify Micrel for any damages resulting from such use or sale.