©2010 Fairchild Semiconductor Corporation
www.fairchildsemi.com
Rev. 1.0.3
Features
• Low Quiescent Current
• Low Dropout Voltage
• Low Temperature Coefficient
• Tight Line and Load Regulation
• Guaranteed 100mA Output Cu rrent
• Internal Short Current & Thermal Limit
• Error Signals of Output Dropout (8 pin Versions only)
• External Shut Down ( 8-Pin Versions Only)
Description
The LP2951 is an adjustable micro power voltage regulator
suitable for use in battery-powered systems. This regulator
has various functions such as alarm which warns of a low
output voltage, often due to falling batte rie s on the input, the
external shutdown which enables the regulator to be
switched on and off, current and temperature limiting.
Internal Block Diagram
[3]
LP2951
Adjustable Micro Power Voltage Regulator
8-SOP
1
LP2951
2
Absolute Maximum Ratings
Parameter Symbol Value Unit
Input Supply Voltage VIN -0.3 ~ +30 V
Power Dissipation PDInternally Limited W
Thermal Resistance Junction-Air RθJA 127.5 °C/W
Storage Temperature Range TSTG -65 ~ +150 °C
Operating Junction Temperature Range TOPR -40 ~ +125 °C
LP2951
3
Electrical Characteristics
(Refer to the test circuit, Ta = 25°C, unless otherwise specified, )
Note :
1. Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total
temperature range.
2. Regulation is measured at constant junction temperature , using pulse testing with a low duty cycle.
3. Vref ≤ Vout ≤ (Vin - 1V), 2.5V ≤ Vin ≤ 28V, 100uA ≤ IL ≤ 100mA, TA ≤ TAMAX .
4. Threshold and hysteresis are expressed in terms of voltage differential at the Feedback terminal below the normal
reference . To express these thresholds in terms of output voltage change , multiply by the error amplifier gain
= VO / VREF = (R1 + R2) / R2 .
5. Vshu tdown ≤ 0.6 V , VOUT =ON , Vshutdown ≥ 2.0 V, VOUT = OFF.
Parameter Symbol Conditions Min. Typ. Max. Unit
ALL VOLTAGE OPTIONS
Output Voltage Temperature Coefficient ΔV/ΔT (Note1) - 50 - ppm/°C
Line Regulation (Note2) ΔV(Vo + 1)V ≤ VIN ≤ 28V
IL = 50mA --0.4%
Load Regulation (Note2) ΔV 100uA ≤ IL ≤ 100mA - - 0.3 %
Dropout Voltage VDIL = 100uA - - 150 mV
IL = 100mA - - 600 mV
Ground Current IGIL = 100uA - - 140 uA
IL = 100mA - - 7 mA
Current Limit ICL VO = 0V 110 165 220 mA
8-PIN VERSIONS ONLY
Reference Voltage VREF VIN = (Vo + 1)V, IL = 100uA 1.235 1.26 1.285 V
VREF (Note3) 1.225 1.26 1.295 V
ERROR COMPARATOR
Output Low Voltage VOL VIN = (Vo - 0.5)V, IOL =400uA - 150 400 mV
High Threshold Voltage VTH (Note4) 25 60 - mV
Low Threshold Voltage VTL (Note4) - 75 140 mV
Hysteresis VHYS (Note4) - 15 - mV
SHUTDOWN INPUT
Shutdown Threshold Range VSD (Note5) 0.6 1.3 2.0 V
Shutdown Input Current ISD VSD = 2.4V - 30 100 uA
VSD = 28V - 450 750 uA
LP2951
4
Typical Performance Characteristics
Figure 1. Quiescent Current Figure 2. Dropout Characteristics
Figure 3. Input Current Figure 4. Input Current
Figure 6. Short Circuit CurrentFigure 5. Output Voltage vs. Temperature
0.1 1 10 100
0.4
0.8
1.2
1.6
2.0
GROUND CURRENT(mA)
LOAD CURRENT(m A )
0 2 4 6 8 10
0
50
100
150
200
250
INPUT CURRENT(u A)
INPUT VOLTAGE(V)
-50 -25 0 25 50 75 100 125
4.94
4.96
4.98
5.00
5.02
5.04
5.06
OUTPUT VOLTAGE(V)
TEMPERATURE(oC)
0123 4 5 6
0
1
2
3
4
5
6
OUTPUT VOLTAGE ( V)
INPUT VOLTAGE(V)
0246 8 10
0
20
40
60
80
100
120
INPUT CURRENT(mA)
INPUT VOL TA GE (V)
-50 -25 0 25 50 75 100 125
100
120
140
160
180
200
SHORT CIRCUIT CURRENT(mA)
TEMPERATURE(oC)
5V OUTPUT RL=50KΩ
RL=50Ω
5V OUTPUT RL=50K
RL=∞
RL=50Ω
5V OUTPUT
LP2951
5
Typical Performance Characteristics (Continued)
TYPICAL PE RF ORMANCE CHARACTERISTICS (Cont inued )
-50-250 255075100125
0
100
200
300
400
500
600
DROPOUT VOLTAGE(V)
TEMPERATURE(oC)
Fig. 7 Dropout
Voltage
0.1 1 10 100
0
100
200
300
400
500
DROPOUT VOLTAGE(mV)
OUTPU T C URRENT(mA)
Fig. 8 Dropout
Voltage
IL = 100mA
IL = 100μA T
J = 25oC
Figure 7. Dropout Voltage Figure 8. Dropout Voltage
LP2951
6
Typical Application
CO is required between the output and ground for stability at output voltages of 5V or more. since IFB is controlled to less
than 40nA, the error associated with this term is negligible in most applications.
At lower output voltage, more capacitance is required. without this capacitance the part will oscillate.
SHUTDOWN
VO = VREF (1+ R
1
/
R2)+IFB R1
V
OU T
VIN
R2
R1Co
1μF
KA78RLOOD
VIN
8
VOUT 1
FB7
VREF
GND
4
5
3
ERROR ERROR
SD
LP2951
LP2951
7
Mechanical Dimension
Package Dimensions in millimeters
8-SOP
4.92 ±0.20
0.194 ±0.008
0.41 ±0.10
0.016 ±0.004
1.27
0.050
5.72
0.225
1.55 ±0.20
0.061 ±0.008
0.1~0.25
0.004~0.001
6.00 ±0.30
0.236 ±0.012
3.95 ±0.20
0.156 ±0.008
0.50 ±0.20
0.020 ±0.008
5.13
0.202 MAX
#1
#4 #5
0~8°
#8
0.56
0.022
()
1.80
0.071
MAX0.10
MAX0.004
MAX
MIN
+0.10
-0.05
0.15+0.004
-0.002
0.006
LP2951
2/1/10 0.0m 001
Stock#DS400464
© 2010 Fairchild Semiconductor Corporation
LIFE SUPPORT POLICY
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES
OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body,
or (b) support or sustain life, and (c) whose failure to
perform when properly used in accordance with
instructions for use provided in the labeling, can be
reasonably expected to result in a significant injury of the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be
reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
www.fairchildsemi.com
DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY
PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRC HILD DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUC T OR CIRCUIT DESCRIBED HEREIN ; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
Ordering Information
Product Number Package Operationg Temperature
LP2951CM 8-SOP -40 ~ +125°C
