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
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.
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
Automotive electronics
Voltage reference
Block Diagram
LP2590 and LP295 1 Block Diagram
(Pin Numbers Refer to LP2591)
Micrel, Inc. LP2950/2951
September 2008 2 M9999-091208
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
* 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.
Micrel, Inc. LP2950/2951
September 2008 3 M9999-091208
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
LP295x-03 (±1%), Note 12 50 150
Output Voltage
Temperature Coefficient
LP2951-4.8 (±1%), Note 12 50 150
LP295x-02 (±0.5%), Notes 14 , 15 0.03
LP295x-03 (±1%), Notes 14, 15 0.04
Line Regulation
LP2951-4.8 (±1%), Notes 14, 15 0.04
LP295x-02 (±0.5%), Note 14, 100µA IL 100mA 0.04
LP295x-03 (±1%), Note 14, 100µA IL 100mA 0.10
Load Regulation
LP2951-4.8 (±1%), Note 14, 100µA IL 100mA 0.10
Micrel, Inc. LP2950/2951
September 2008 4 M9999-091208
Parameter Condition Min Typ Max Units
Note 5, IL = 100µA 50
Dropout Voltage
Note 5, IL = 100mA 380
IL = 100µA 100 150
Ground Current
IL = 100mA 8 12
Dropout Current VIN = 4.5V, IL = 100µA 180 250
Current Limit VOUT = 0V 160 220
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
1.235 1.250
LP295x-03 (±1%) 1.210
1.235 1.260
Reference Voltage
LP2951-4.8 (±1%) 1.210
1.235 1.260
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
Output Low Voltage (Flag) VIN = 4.5V, IOL = 200µA 150 250
Upper Threshold Voltage Note 6 40
60 mV
Lower Threshold Voltage Note 6 75
Hysteresis Note 6 15 mV
Micrel, Inc. LP2950/2951
September 2008 5 M9999-091208
Parameter Condition Min Typ Max Units
LP295x-02 (±0.5%)
0.7 V
LP295x-03 (±1%)
0.7 V
Input Logic Voltage
LP2951-4.8 (±1%)
0.7 V
VSHUTDOWN = 2.4V 30 50
Shutdown Input Current
VSHUTDOWN = 30V 450 600
Regulator Output Current
in Shutdown
Note 11 3
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
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%
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.
Micrel, Inc. LP2950/2951
September 2008 6 M9999-091208
Typical Characteristics
Micrel, Inc. LP2950/2951
September 2008 7 M9999-091208
Typical Characteristics (continued)
Micrel, Inc. LP2950/2951
September 2008 8 M9999-091208
Typical Characteristics (continued)
Micrel, Inc. LP2950/2951
September 2008 9 M9999-091208
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-
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 1M. 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:
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 1.2M 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 = 100k
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.
Micrel, Inc. LP2950/2951
September 2008 10 M9999-091208
Noise can be reduced fourfold by a bypass capacitor
across R1, since it reduces the high frequency gain from
4 to unity. Pick:
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
Micrel, Inc. LP2950/2951
September 2008 11 M9999-091208
Typical Applications
Wide Input Voltage Range Current Limiter 5V Regulator with 2.5V Sleep Function
Low Drift Current Source 5V Current Limiter
Micrel, Inc. LP2950/2951
September 2008 12 M9999-091208
Typical Applications
Regulator with Early Warning and Auxiliary Output
Micrel, Inc. LP2950/2951
September 2008 13 M9999-091208
Typical Applications
Latch Off When Error Flag Occurs Open Circuit Detector for 4mA to 20mA Current Loop
Regulator with State-of-Charge Indicator
Micrel, Inc. LP2950/2951
September 2008 14 M9999-091208
Typical Applications
Low Battery Disconnect
System Over Temperature Pro t ectio n Circuit
Micrel, Inc. LP2950/2951
September 2008 15 M9999-091208
Schematic Diagram
Micrel, Inc. LP2950/2951
September 2008 16 M9999-091208
Package Information
8-Pin SOIC (M)
0.380 (9.65)
0.370 (9.40) 0.135 (3.43)
0.125 (3.18)
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)
Micrel, Inc. LP2950/2951
September 2008 17 M9999-091208
10° typ.
5° 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
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)
TO-92 (Z)
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.
© 1999 Micrel, Incorporated.