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LP2951
Adjustable Micro Power Voltage Regulator
Features
* * * * * * * * Low Quiescent Current Low Dropout Voltage Low Temperature Coefficient Tight Line and Load Regulation Guaranteed 100mA Output Current 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 batteries on the input, the external shutdown which enables the regulator to be switched on and off, current and temperature limiting.
8-SOP
1
Internal Block Diagram
OUT(1)
INPUT(8)
+
PROGRAM (2)
ERROR AMPLIFIER
+
FEEDBACK(7)
C1 SHUTDOWN(3)
+ OFFSE TAP(6)
FROM EXTERNAL INPUT
SCP
T ERROR COMPARATO 1.25V + COMPARATOR R REFERENCE TO EXTERNAL INPUT
+
GROUND(4)
ERROR(5)
Rev. 1.0.0
(c)2001 Fairchild Semiconductor Corporation
LP2951
Absolute Maximum Ratings
Parameter Input Supply Voltage Power Dissipation Thermal Resistance Junction-Air Storage Temperature Range Operating Junction Temperature Range Symbol VIN PD RJA TSTG TOPR Value -0.3 ~ +30 Internally Limited 127.5 -65 ~ +150 -40 ~ +125 Unit V W C/W C C
2
LP2951
Electrical Characteristics
(Refer to the test circuit, Ta = 25 C, unless otherwise specified, ) Parameter ALL VOLTAGE OPTIONS Output Voltage Temperature Coefficient Line Regulation (Note2) Load Regulation (Note2) Dropout Voltage Ground Current Current Limit 8-PIN VERSIONS ONLY Reference Voltage ERROR COMPARATOR Output Low Voltage High Threshold Voltage Low Threshold Voltage Hysteresis SHUTDOWN INPUT Shutdown Threshold Range Shutdown Input Current VSD ISD (Note5) VSD = 2.4V VSD = 28V 0.6 1.3 30 450 2.0 100 750 V uA uA VOL VTH VTL VHYS VIN = (Vo - 0.5)V, IOL =400uA (Note4) (Note4) (Note4) 25 150 60 75 15 400 140 mV mV mV mV VREF VREF (Note3) 1.235 1.26 1.285 1.225 1.26 1.295 V V V/T V V VD IG ICL (Note1) (Vo + 1)VVIN28V IL = 50mA 100uA IL100mA IL = 100uA IL = 100mA IL = 100uA IL = 100mA VO = 0V 110 50 165 0.4 0.3 150 600 140 7 220 ppm/C % % mV mV uA mA mA Symbol Conditions Min. Typ. Max. Unit
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. Vshutdown 0.6 V , VOUT =ON , Vshutdown 2.0 V, VOUT = OFF.
3
LP2951
Typical Performance Characteristics
2.0
6
GROUND CURRENT(mA)
O UT P UT VOL T A G E (V
5
1.6
5V OUTPUT
RL=50K RL=50
4
1.2
3
0.8
2
0.4
1
0
0.1 1 10 100
0
1
2
3
4
5
6
LOAD CURRENT(mA)
INP UT VO L T A G E (V)
Figure 1. Quiescent Current
Figure 2. Dropout Characteristics
250
120
5V OUTPUT
INPUT CURRENT(uA)
RL=50 RL=50K
INPUT CUR RE NT(mA)
100
200
80
150
60
100
RL=
40
50
20
0 0 2 4 6 8 10
0
0
2
4
6
8
10
INPUT VOLTAGE(V)
INPUT VOLT AGE (V)
Figure 3. Input Current
Figure 4. Input Current
5.06
200 S HO R T C IR C UIT C UR R E NT (m A
25 50 75 100 125
5.04
5V OUTPUT
OUTPUT VOLTAGE(V)
180
5.02
160
5.00
4.98
140
4.96
120
4.94 -50 -25 0
100 -5 0
-2 5
0
25
50
75
100
125
TEMPERATURE(oC)
T E M P E R A T UR E ( o C )
Figure 5. Output Voltage vs. Temperature
Figure 6. Short Circuit Current
4
LP2951
Typical Performance Characteristics (Continued)
TYPICAL PERFORMANCE CHARACTERISTICS (Continued )
600
Fig. 7 Dropout Voltage
I = 100mA
L
Fig. 8 Dropout Voltage
500
500
400
400
DROPOUT VOLTAGE(mV)
DROPOUT VOLTAGE(V)
300
300
200
200
100
IL = 100 A
100
J T = 25 C
o
0 -50
-25
0
25
50
o
75
100
125
0 0.1
1
10
100
TEMPERATURE( C)
OUTPUT CURRENT(mA)
Figure 7. Dropout Voltage
Figure 8. Dropout Voltage
5
LP2951
Typical Application
VIN
8 ERROR SHUTDOWN 5 ERROR V 1 OUT KA78RLOOD LP2951 3
SD GND FB VIN
VOUT Co 1 F
R1 7 VREF R2
4
VO = VREF (1+ R / R2)+IFB R1 1
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.
6
LP2951
Mechanical Dimension
Package Dimensions in millimeters
8-SOP
MIN 1.55 0.20 0.061 0.008 0.1~0.25 0.004~0.001
#1
#8
4.92 0.20 0.194 0.008 5.13 MAX 0.202
(
0.56 ) 0.022
#4
#5
6.00 0.30 0.236 0.012
+0.10 0.15 -0.05 +0.004 0.006 -0.002
1.80 MAX 0.071
MAX0.10 MAX0.004
3.95 0.20 0.156 0.008
5.72 0.225 0.50 0.20 0.020 0.008
0~ 8
1.27 0.050
0.41 0.10 0.016 0.004
7
LP2951
Ordering Information
Product Number LP2951CM Package 8-SOP Operationg Temperature -40 ~ +125C
8
LP2951
9
LP2951
DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. 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.
www.fairchildsemi.com 5/19/01 0.0m 001 Stock#DSxxxxxxxx 2001 Fairchild Semiconductor Corporation
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.

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