1
Rev G LP2950-51 Low Dropout Linear Regulators © 2008 Exar Corporation
Now Available in Lead Free Packaging
INPUT OUTPUT
UNREGULATED DC
SHUTDOWN
GROUND
ERROR
______
SENSE
5V @ 100mA
MAX
TO CMOS OR
TTL
REFERENCE
ERROR DETECTION
COMPARATOR
ERROR
AMPLIFIER
1.23V
FROM
CMOS OR
TTL
+
+
+
+
+
+
60 mV
3
781
2
6
5
4
60k
Ω
330k
Ω
180k
Ω
.
.
1µF
_
_
FEEDBACK
5V TAP
 
•       •  
•     • 
•       •  
•      •  
•     •  
•     • 
•    µ   •
•   Lead Free, RoHS Compliant Packages:
    
• 
•   
• 
• 
  
•      
•   
•      
 
                  
                
                    
                  
        
                      
                   
              
   
LP2950/LP2951
100mA, LOW DROPOUT VOLTAGE REGULATORS
OCTOBER 6, 2008 REV. G
2© 2008 Exar Corporation

  
        
          
              
           
     
 

 
 

   

  
 


  


   
  
   
 ≤ ≤
  


















   µ≤
≤ 
≤

     
  
   
 ≤ ≤
  


















   µ≤
≤ 
≤

     
  
 
   
    
     ≤ ≤      
     µ≤
≤     
 
 
  µ
  










 
  µ
  






µ

 

      
      
 
 µ   µ 
  
  µ   µ 
  µ   
      
  µ 
    
       
         
  

    
Rev G LP2950-51 Low Dropout Linear Regulators
© 2008 Exar Corporation
LP2950/51
PARAMETER
CONDITIONS
(Note 2)
LP2951AC
Min. Typ.
Max.
LP2951C
Min. Typ. Max.
UNITS
8-Pin Versions only (Continued)
Reference Voltage
Temperature
Coefficient
20 50 ppm/°C
Feedback Pin Bias
Current
Temperature
Coefficient
0.1 0.1 nA/°C
Error Comparator
Output Leakage
Current
V
OH
= 30V 0.01 1 0.01 1 μA
Output Low Voltage VIN= 4.5V
IOL= 400 μA
150 250 150 250 mV
Upper Threshold
Voltage
(Note 7) 40 60 40 60 mV
Lower Threshold
Voltage
(Note 7) 75 95 75 95 mV
Hysteresis (Note 7) 15 15 mV
Shutdown Input
Input logic Voltage Low (Regulator ON)
High (Regulator OFF)
2.0
1.3 0.7
2.0
1.3 0.7 V
V
Shut down Pin Input
Current
VS= 2.4V
VS= 30V
30
675
50
800
30
675
50
800
μA
μA
Regulator Output
Current in Shutdown
(Note 8) 3 10 3 10 μA
8 Pin SOIC
128. 4
°C/W
Thermal
Resistance θ
JA
3 Pin TO-92
131.
9
°C/W
Note 1: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the t otal temperature range.
Note 2: Unless otherwise specified all limits guaranteed for T
J
= 25°C, V
IN
= 6V, I
L
= 100 μA and C
L
= 1μF. Additional conditions for the 8-pin versions are feedback
tied to 5V tap and output tied to output sense (V
OUT
= 5V) and V
SHUTDOWN
≤0.8V.
Note 3: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes i n output voltage due to heating effects are
covered under the specification for thermal regulation.
Note 4: Line regulation for the LP2951 is tested at I
L
= 1mA. For I
L
= 100 μA and T
J
= 125°C, line regulation is guaranteed by design to 0.2%. See typical
performance characteristics for line regulation versus temperature and load current.
Note 5: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV 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 ta ken into account.
Note 6: V
REF
≤V
OUT
≤(V
IN
- 1V), 2.3 ≤V
IN
≤30V, 100μA≤I
L
≤100mA, T
J
≤T
JMAX
.
Note 7: Comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nomi nal reference voltage measured at 6V input. To
express these thresholds in terms of output voltage change, multiply by the error amplifier gain = V
OUT
/V
REF
= (R
1
+ R
2
)/R
2
. For example, at a programmed output
voltage of 5V, the error output is guaranteed to go low when the output drops by 95 mV x 5V/1.235 = 384 mV. Thresholds remain constant as a percent of V
OUT
as V
OUT
is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
Note 8: V
SHUTDOWN
≥2V, V
IN
≤30V, V
OUT
=0, Feedback pin tied to 5V Tap.
Note 9: All typical values are not guaranteed. The value could vary from lot to lot.
Rev G LP2950-51 Low Dropout Linear Regulators
3
© 2008 Exar Corporation
Input Current
INPUT CURRENT (µ A )
75
0
0 10
INPUT VOLTAGE (VOLTS)
R
L
= 50k Ω
25
50
100
125
150
175
200
225
250
1 2 3
R
L
=
8
Dropout Characteristics
OUTPUT VOLTAGE (VOLTS)
00
INPUT VOLTAGE (VOLTS)
1 2 3 4 5 6
1
2
3
4
5
6
R
L
=
R
L
=50kΩ
4 5 6 7 8 9
LOAD CURRENT (mA)
Quiescent Current
GROUND PIN CU RRENT (mA)
10
1
0.1
0.01
0.1 1 10 100
Ground Current
GROUND CUR RENT (µA)
320
280
0
INPUT VOLTAGE (VOLTS)
240
80
40
01 2 3 4 5 6 7 8
120
160
200
I
L
= 1mA
I
L
= 0
INPUT VOLTAGE (VOLTS)
Input Current
INPUT CUR RENT (mA)
160
150
140
130
70
50
0
120
110
100
90
80
60
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10
R
L
=50
Ω
V
OUT
= 5V
Quiescent Current
190
170
150
130
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (ºC)
QUIESCENT CURRENT (µ A)
V
IN
=6V
I
L
=100uA
Ground Current
16
14
12
012 3 4 5 6 7 8
INPUT VOLTAGE
GROUND CUR RENT (mA)
108
6
4
2
0
I
L
=100mA
Ground Current
16
12
8
4
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (ºC)
GROUND CUR RENT (mA)
V
IN
= 6V
I
L
= 100mA
 
  
8
Rev G LP2950-51 Low Dropout Linear Regulators
4
7
5© 2008 Exar Corporation
LP2951 Comparator Sink Current
SINK CURRENT (mA)
2.5
1.5
OUTPUT LOW VOLTAGE (V)
2.0
1.0
0.5
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
T
A
= -55ºC
T
A
= 25ºC
T
A
= 125ºC
Line Transient Response
TIME(µs)
100
0 200 400 600 800
INPUT OUTPUT VOLTAGE
VOLTAGE CHANGE
4V
6V
8V
-50
0
50
~
~
mV
mV
mV
C
L
= 1 µF
I
L
= 1mA
V
OUT
= 5V
Error Comparator Output
COMPARATOR OUTPUT (V)
8
6
0
INPUT VOLTAGE (V)
4
2
0
-2
1 2 3 4 5
V
OUT
= 5V
PULLUP RESISTOR TO
SEPARATE 5V SUPPLY
HYSTERESIS
Output Impedance
10
0.5
0.1
0.02
10 100 1K 10K 100K 1M
FREQUENCY (Hz)
OUTPUT IMPEDANCE (OHMS)
5
0.2
0.05
0.01
1
2
I
O
= 100mA
I
O
= 100 µA
I
O
= 1mA
V
OUT
= 5V
C
L
= 1 µF
Ripple Rejection
90
70
60
40
10
1
10
2
10
3
10
4
10
5
10
6
FREQUENCY (Hz)
RIPPLE REJECTION (dB)
80
50
20
30
I
L
= 100 µA
I
L
= 0
C
L
= 1 µF
V
IN
= 6V
V
OUT
= 5V
Ripple Rejection
FREQUENCY (Hz)
RIPPLE REJECTION (dB)
10
6
10
3
10
2
10
1
90
80
70
60
50
20
40
30
10
4
10
5
I
L
= 10mA
I
L
= 1mA
C
L
= 1µF
V
IN
= 6V
V
OUT
= 5V
Drop-Out Voltage
600
400
300
50
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (ºC)
DROP-OUT VOLTAGE (mV)
500
100
0
I
L
= 100mA
I
L
= 100 µA
~
~
Drop-Out Voltage
T
J
= 25ºC
OUTPUT CURRENT
DROP-OUT VOLTAGE (mV)
100mA
10mA
1mA100µA
500
400
300
200
100
0
Short Circuit Current
SHORT CIRCUIT CURRENT (mA)
170
150
130
110
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (ºC)
160
140
120
110

   
Rev G LP2950-51 Low Dropout Linear Regulators
© 2008 Exar Corporation
LP2951 Feedback Bias Current
BIAS CURRENT (nA)
-30-75
TEMPEATURE (ºC)
-50 0 50 75 100 150
-20
-10
0
10
20
-25 25 125
LP2951 Feedback Pin Current
FEEDBACK CURRENT (µA)
-150
-250
-2.0 -0.5 1.0
FEEDBACK VOLTAGE (V)
-200
-100
-50
0
50
-1.5 -1.0
0 0.5
T
A
= 25ºC
T
A
= 55ºC
TA=1 25ºC
PIN 7 DRIVEN BY EXTERNAL
SOURCE (REGULATOR RUN
OPEN LOOP)
LP2951 Minimum Operating Voltage
TEMPERATURE
MINIMUM OPERATING VOLTAGE (V)
2.3
2.1
1.9
1.7-75 0 75 150
-50 -25 25 50 100 125
Load Transient Response
250
100
-50
100
0 1 2 3 4 5
TIME (ms)
LOAD OUTPUT VOLTAGE
CURRENT CHANGE (mV)
µA
~
~
mA
-100
0
50
150
200
C
L
= 1 µF
V
OUT
= 5V
100
Load Transient Response
80
20
-40
100
0 4 8 12 16 20
TIME (ms)
LOAD OUTPUT VOLTAGE
CURRENT CHANGE (mV)
µA
100
-60
-20
0
40
60
µA
C
L
= 10 µF
V
OUT
= 5V
~
~
LP2950 Maxium Rated Output
OUTPUT CURRENT (mA)
120
80
0
0 10 20 30
INPUT VOLTAGE (V)
2515
5
T
A
= 85 ºC
T
A
=25 ºC
T
JMAX
= 125 ºC
0.25" LEADS SOLDERED
TO-92 PACKAGE
TO PC BOARD
100
60
40
20
Vout=5V
LP2950 Maxium Rated Output Current
OUTPUT CURRENT (mA)
120
100
60
40
0
INPUT VOLTAGE (V)
80
20
0
5 10 15 20 25 30
T
JMAX
= 125º C
V
OUT
= 5V
T
A
= 25ºC
T
A
= 50ºC
T
A
= 85ºC
8-PIN
MOLDED
TO PC BOARD
DIP SOLDERED
Enable Transient
7
6
4
-100 0100 200 300 400 500 600 700
TIME (us)
SHUTDOWN OUTPUT
PINOUT V O L T A GE (V) VOLTAGE (V)
3
2
1
0
2
-2
0
5
OUT
= 5V
V
IN
= 8V
I
L
= 10mA
V
LP2951 Divider Resistance
PIN 2 T O PIN 4 RESISTANCE (kΩ)
400
200
100
0
-75 0 75 150
TEMPERATURE (ºC)
-50 -25 25 50 100 125
300
C
L
= 1 µF
C
L
= 10 µF

   
Rev G LP2950-51 Low Dropout Linear Regulators
6
© 2008 Exar Corporation
  
   




 




       
 
  
   
 µ


    

 
 
  µ 








  






 µ
 
  








 
  µ
 
  µ

 

 






 
   




  




    
  µ
 
  
  
  µ
 µ

  µ
 
  µ

 
Rev G LP2950-51 Low Dropout Linear Regulators
7
8© 2008 Exar Corporation
Rev G LP2950-51 Low Dropout Linear Regulators
9© 2008 Exar Corporation

 
100K
OUTPUT
ERROR
ERROR
______
SD
V
OUT
GND FB
+V
IN
+V
IN
1.23V
1.2
4
to 2
9
V
R
1
.01µF
3.3µF
R
2
V
REF
3
8
5
1
47
SHUTDOWN
INPUT
+
LP2951
470kΩ
ERROR
______
SD
V
OUT
GND
+V
IN
+V
IN
R
1
1µF
R
2
3
8
5
1
4
+
FB
7
V
OUT
470kΩ
LP2951
RESET
OUTPUT
ERROR
ERROR
______
SD
V
OUT
GND FB
+V
IN
+V
IN
*V
OUT
= V
IN
3
8
5
1
47
SHUTDOWN
INPUT
LP2951
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV to 400mV.
DEPENDING ON LOAD CURRENT. CURRENT LIMIT IS TYPICALLY 150mA
   
               
Rev G LP2950-51 Low Dropout Linear Regulators
10© 2008 Exar Corporation

  
100kΩ
SENSE
SD
V
OUT
GND
+V
IN
3
8
1
1µF
+
4
400
kΩ
120kΩ 1.5kΩ
6V
SEALED
LEAD-
ACID
BATTERY
SOURCE FB
FOR 5.5 V
+
1N457
2
20kΩ
NI-CAD
BACKUP
BATTERY
MEMORY V+
MAIN V+
SPX385
LP2951




































Ω

Ω

Ω

Ω

Ω

Ω

Ω

Ω

Ω

Ω



 

            

 
   

   

    
      
Rev G LP2950-51 Low Dropout Linear Regulators
11
042408 Rev F LP2950-51 Low Dropout Linear Regulator © 2008 Exar Corporation
EXTERNAL CIRCUIT
PROTECTED FROM
OVER TEMPERATURE
(V+ GOES OFF WHEN
TEMP > 125)
OR
RELAY
8.2K
TEMP
SENSOR
GND
V
OUT
FB
SD +V
IN
+V
IN
10K
5 DEGREE SHUTDOWN FLAG
ERROR
_______
35
8
4
7
1
AUX SHUTDOW
INPUT
OFF
ON
Ω
AS35
+
-
LP2951
Ω
.
.
330K
IN V
OUT
FB
6
81
4.7µF
+
7
Ω
Ω
27K
LP2951
V
TAP
GND
SENSE
4
2
UNREGULATED INPUT
2N5432
5V
OUTPUT
LOAD
50mA
TO
300 mA
(2)
360K
0.1µF
V
OUT
MIN VOLTAGE = 4V
+V
IN
8
1
FB 7
1N4001
20mA
1N457
4.7mA
+5V
OUTPUT
2
GND
4
4
LP2951
Ω

  
     
         

     
12 © 2008 Exar Corporation
PACKAGE: 3 PIN TO-92
Rev G LP2950-51 Low Dropout Linear Regulators
13 © 2008 Exar Corporation
PACKAGE: 3 PIN TO-92 AMMO PACK
Rev G LP2950-51 Low Dropout Linear Regulators
14 © 2008 Exar Corporation
PACKAGE: 8 PIN NSOIC
Rev G LP2950-51 Low Dropout Linear Regulators
15
 
100K
OUTPUT
ERROR
ERROR
______
SD
V
OUT
GND FB
+V
IN
+V
IN
1.23V
1.2
4
to 2
9
V
R
1
.01µF
3.3µF
R
2
V
REF
3
8
5
1
47
SHUTDOWN
INPUT
+
LP2951
470kΩ
ERROR
______
SD
V
OUT
GND
+V
IN
+V
IN
R
1
1µF
R
2
3
8
5
1
4
+
FB
7
V
OUT
470kΩ
LP2951
RESET
OUTPUT
ERROR
ERROR
______
SD
V
OUT
GND FB
+V
IN
+V
IN
*V
OUT
= V
IN
3
8
5
1
47
SHUTDOWN
INPUT
LP2951
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV to 400mV.
DEPENDING ON LOAD CURRENT. CURRENT LIMIT IS TYPICALLY 150mA
   
               
ORDERING INFORMATION
Part Number Accuracy Output
Voltage Package Shipping Status
LP2950ACN-L-3-3 0.50% 3.3V Lead Free
3 Pin TO-92 Bulk Active
LP2950ACN-L-3-3/TR 0.50% 3.3V Lead Free
3 Pin TO-92 Tape & Reel Active
LP2950ACN-L-5-0 0.50% 5.0V Lead Free
3 Pin TO-92 Bulk Active
LP2950ACN-L-5-0/TR 0.50% 5.0V Lead Free
3 Pin TO-92 Tape & Reel Active
LP2950CN-L-3-3 1% 3.3V Lead Free
3 Pin TO-92 Bulk Active
LP2950CN-L-3-3/TR 1% 3.3V Lead Free
3 Pin TO-92 Tape & Reel Active
LP2950CN-L-5-0 1% 5.0V Lead Free
3 Pin TO-92 Bulk Active
LP2950CN-L-5-0/TR 1% 5.0V Lead Free
3 Pin TO-92 Tape & Reel Active
LP2951ACS-L-3-3 0.50% 3.3V Lead Free
8 Pin SOIC Bulk Active
LP2951ACS-L-3-3/TR 0.50% 3.3V Lead Free
8 Pin SOIC Tape & Reel Active
LP2951ACS-L-5-0 0.50% 5.0V/ADJ Lead Free
8 Pin SOIC Bulk Active
LP2951ACS-L-5-0/TR 0.50% 5.0V/ADJ Lead Free
8 Pin SOIC Tape & Reel Active
LP2951CS-L-3-3 1% 3.3V Lead Free
8 Pin SOIC Bulk Active
LP2951CS-L-3-3/TR 1% 3.3V Lead Free
8 Pin SOIC Tape & Reel Active
LP2951CS-L-5-0 1% 5.0V/ADJ Lead Free
8 Pin SOIC Bulk Active
LP2951CS-L-5-0/TR 1% 5.0V/ADJ Lead Free
8 Pin SOIC Tape & Reel Active
© 2008 Exar Corporation
Rev G LP2950-51 Low Dropout Linear Regulators
16 © 2008 Exar Corporation
Part Number Accuracy Output
Voltage Package Shipping Status
LP2950ACN-3-3 0.50% 3.3V 3 Pin TO-92 Bulk EOL
LP2950ACN-5-0 0.50% 5.0V 3 Pin TO-92 Bulk EOL
LP2950CN-3-3 1% 3.3V 3 Pin TO-92 Bulk EOL
LP2950CN-3-3/TR 1% 3.3V 3 Pin TO-92 Tape & Reel EOL
LP2950CN-5-0 1% 5.0V 3 Pin TO-92 Bulk EOL
LP2950CN-5-0/TR 1% 5.0V 3 Pin TO-92 Tape & Reel EOL
LP2951ACS-3-3 0.50% 3.3V 8 Pin SOIC Bulk EOL
LP2951ACS-5-0 0.50% 5.0V/ADJ 8 Pin SOIC Bulk EOL
LP2951CS-3-3 1% 3.3V 8 Pin SOIC Bulk EOL
LP2951CS-3-3/TR 1% 3.3V 8 Pin SOIC Tape & Reel EOL
LP2951CS-5-0 1% 5.0V/ADJ 8 Pin SOIC Bulk EOL
LP2951CS-5-0/TR 1% 5.0V/ADJ 8 Pin SOIC Tape & Reel EOL
LP2950ACN-3-3/TR 0.50% 3.3V 3 Pin TO-92 Tape & Reel OBS
LP2950ACN-5-0/TR 0.50% 5.0V 3 Pin TO-92 Tape & Reel OBS
LP2951ACS-3-3/TR 0.50% 3.3V 8 Pin SOIC Tape & Reel OBS
LP2951ACS-5-0/TR 0.50% 5.0V/ADJ 8 Pin SOIC Tape & Reel OBS
ORDERING INFORMATION
(continued)
Exar Corporation
Headquarters and
Sales Office
48720 Kato Road
Fremont, CA 94538
main: 510-668-7000
fax: 510-668-7030
EXAR Corporation reserves the right to make changes to the products contained in this publication in order
to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any
circuits described herein, conveys no license under any patent or other right, and makes no representation
that the circuits are free of patent infringement. Charts and schedules contained here in are only for
illustration purposes and may vary depending upon a user’s specific application. While the information in this
publication has been carefully checked; no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the
failure or malfunction of the product can reasonably be expected to cause failure of the life support system or
to significantly affect its safety or effectiveness. Products are not authorized for use in such applications
unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or
damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation
is adequately protected under the circumstances.
Rev G LP2950-51 Low Dropout Linear Regulators