LP2956/LP2956A
Dual Micropower Low-Dropout Voltage Regulators
General Description
The LP2956 is a micropower voltage regulator with very low
quiescent current (170 A typical at light loads) and very low
dropout voltage (typically 60 mV at 1 mA load current and
470 mV at 250 mA load current on the main output).
The LP2956 retains all the desirable characteristics of the
LP2951, but offers increased output current (main output),
an auxiliary LDO adjustable regulated output (75 mA), and
additional features.
The auxiliary output is always on (regardless of main output
status), so it can be used to power memory circuits.
Quiescent current increases only slightly at dropout, which
prolongs battery life.
The error flag goes low if the main output voltage drops out
of regulation.
An open-collector auxiliary comparator is included, whose in-
verting input is tied to the 1.23V reference.
Reverse battery protection is provided.
The parts are available in DIP and surface mount packages.
Features
n
Output voltage adjusts from 1.23V to 29V
n
Guaranteed 250 mA current (main output)
n
Auxiliary LDO (75 mA) adjustable output
n
Auxiliary comparator with open-collector output
n
Shutdown pin for main output
n
Extremely low quiescent current
n
Low dropout voltage
n
Extremely tight line and load regulation
n
Very low temperature coefficient
n
Current and thermal limiting
n
Reverse battery protection
Applications
n
High-efficiency linear regulator
n
Low dropout battery-powered regulator
n
P system regulator with switchable high-current V
CC
Block Diagram
LP2956
DS011339-1
May 1999
LP2956/LP2956A
Dual
Micropower
Low-Dropout
V
oltage
Regulators
1999 National Semiconductor Corporation
DS011339
www.national.com
Connection Diagrams
16Pin DIP
DS011339-2
Order Number LP2956IN or LP2956AIN
See NS Package Number N16A
Order Number LP2956AMJ-QML or 5962-9554701QEA
See NS Package Number J16A
16-Pin Surface Mount
DS011339-3
Order Number LP2956IM or LP2956AIM
See NS Package Number M16A
www.national.com
2
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Storage Temperature Range
-65C to +150C
Operating Junction
Temperature Range
-40C to +125C
Lead Temperature
(Soldering, 5 seconds)
260C
Power Dissipation (Note 2)
Internally Limited
Input Supply Voltage
-20V to +30V
Feedback Input Voltage (Note 3)
-0.3V to +5V
Aux. Feedback Input Voltage (Note 3)
-0.3V to +5V
Shutdown Input Voltage (Note 3)
-0.3V to +30V
Comparator Input Voltage (Notes 3,
4)
-0.3V to +30V
Comparator Output Voltage (Notes 3,
4)
-0.3V to +30V
ESD Rating (Note 16)
2 kV
Electrical Characteristics
Limits in standard typeface are for T
J
= 25C, and limits in boldface type apply over the full operating temperature range. Lim-
its are guaranteed by production testing or correlation techniques using standard Statistical Quality Control (SQC) methods.
Unless otherwise specified: V
IN
= 6V, C
L
= 2.2 F (Main Output) and 10 F (Auxiliary Output), Feedback pin is tied to 5V Tap
pin, C
IN
= 1 F, V
SD
= 0V, Main Output pin is tied to Output Sense pin, Auxiliary Output is programmed for 5V. The main
regulator output has a 1 mA load, the auxiliary regulator output has a 100 A load.
Symbol
Parameter
Conditions
Typical
LP2956AI
LP2956I
Units
Min
Max
Min
Max
MAIN OUTPUT
V
O
Output Voltage
5.0
4.975
5.025
4.950
5.050
4.940
5.060
4.900
5.100
V
1 mA
I
L
250 mA
5.0
4.930
5.070
4.880
5.120
Temperature Coefficient
(Note 5)
20
100
150
ppm/C
Line Regulation
V
IN
= 6V to 30V
0.03
0.1
0.2
%
0.2
0.4
Load Regulation
I
L
= 1 mA to 250 mA
0.04
0.16
0.20
%
I
L
= 0.1 mA to 1 mA (Note 6)
0.20
0.30
V
IN
V
O
Dropout Voltage
I
L
= 1 mA
60
100
100
(Note 7)
150
150
I
L
= 50 mA
240
300
300
420
420
mV
I
L
= 100 mA
310
400
400
520
520
I
L
= 250 mA
470
600
600
800
800
I
LIMIT
Current Limit
R
L
= 1
380
500
500
mA
530
530
Thermal Regulation
(Note 8)
0.05
0.2
0.2
%/W
e
n
Output Noise Voltage
C
L
= 2.2 F
400
(10 Hz to 100 KHz)
C
L
= 33 F
260
V RMS
I
L
= 100 mA
C
L
= 33 F (Note 9)
80
V
FB
Feedback Pin Voltage
1.23
1.215
1.245
1.205
1.255
V
I
FB
Feedback Pin Bias
20
40
40
nA
Current
60
60
I
O
Output Leakage
I
(SD IN)
1 A
3
10
10
A
(OFF)
In Shutdown
V
IN
= 30V, V
OUT
= 0V
20
20
AUXILIARY OUTPUT
V
FB
Feedback Pin Voltage
1.23
1.22
1.25
1.21
1.26
V
1.21
1.26
1.20
1.27
www.national.com
3
Electrical Characteristics
(Continued)
Limits in standard typeface are for T
J
= 25C, and limits in boldface type apply over the full operating temperature range. Lim-
its are guaranteed by production testing or correlation techniques using standard Statistical Quality Control (SQC) methods.
Unless otherwise specified: V
IN
= 6V, C
L
= 2.2 F (Main Output) and 10 F (Auxiliary Output), Feedback pin is tied to 5V Tap
pin, C
IN
= 1 F, V
SD
= 0V, Main Output pin is tied to Output Sense pin, Auxiliary Output is programmed for 5V. The main
regulator output has a 1 mA load, the auxiliary regulator output has a 100 A load.
Symbol
Parameter
Conditions
Typical
LP2956AI
LP2956I
Units
Min
Max
Min
Max
AUXILIARY OUTPUT
Feedback Voltage
Temperature Coefficient
20
ppm/C
I
FB
Feedback Pin Bias
10
20
20
nA
Current
30
30
Line Regulation
6V
V
IN
30V
0.07
0.3
0.4
%
0.5
0.6
Load Regulation
I
L
= 0.1 mA to 1 mA
0.1
0.3
0.4
%
I
L
= 1 mA to 75 mA (Note 10)
0.6
1.0
V
IN
V
O
Dropout Voltage
I
L
= 1 mA
100
200
200
mV
300
300
I
L
= 50 mA
400
600
600
mV
700
700
I
L
= 75 mA
500
700
700
mV
850
850
e
n
Output Noise
C
L
= 10 F
300
(10 Hz100 KHz)
C
L
= 33 F (Note 9)
100
V RMS
I
L
= 10 mA
I
LIM
Current Limit
V
OUT
= 0V (Note 13)
80
200
200
mA
250
250
Thermal Regulation
(Note 8)
0.2
0.5
0.5
%/W
DROPOUT DETECTION COMPARATOR
I
OH
Output "HIGH" Leakage
V
OH
= 30V
0.01
1
1
A
2
2
V
OL
Output "LOW" Voltage
V
IN
= 4V
150
250
250
mV
I
O
(COMP) = 400 A
400
400
V
THR
Upper Threshold Voltage
(Note 11)
-240
-320
-150
-320
-150
mV
(max)
-380
-100
-380
-100
V
THR
Lower Threshold Voltage
(Note 11)
-350
-450
-230
-450
-230
mV
(min)
-640
-160
-640
-160
HYST
Hysteresis
(Note 11)
110
mV
SHUTDOWN INPUT
I
IN
Input Current to Disable
Output
(Note 12)
0.03
0.5
0.5
A
V
IH
Shutdown Input High
I
(SD IN)
1 A
900
900
mV
Threshold
1200
1200
V
IL
Shutdown Input Low
V
O
4.5V
400
400
mV
Threshold
200
200
AUXILIARY COMPARATOR
V
T
(high)
Upper Trip Point
(Note 14)
1.236
1.20
1.28
1.20
1.28
V
1.19
1.29
1.19
1.29
V
T
(low)
Lower Trip Point
(Note 14)
1.230
1.19
1.27
1.19
1.27
V
1.18
1.28
1.18
1.28
www.national.com
4
Electrical Characteristics
(Continued)
Limits in standard typeface are for T
J
= 25C, and limits in boldface type apply over the full operating temperature range. Lim-
its are guaranteed by production testing or correlation techniques using standard Statistical Quality Control (SQC) methods.
Unless otherwise specified: V
IN
= 6V, C
L
= 2.2 F (Main Output) and 10 F (Auxiliary Output), Feedback pin is tied to 5V Tap
pin, C
IN
= 1 F, V
SD
= 0V, Main Output pin is tied to Output Sense pin, Auxiliary Output is programmed for 5V. The main
regulator output has a 1 mA load, the auxiliary regulator output has a 100 A load.
Symbol
Parameter
Conditions
Typical
LP2956AI
LP2956I
Units
Min
Max
Min
Max
AUXILIARY COMPARATOR
HYST
Hysteresis
6
mV
I
OH
Output "HIGH" Leakage
V
OH
= 30V
0.01
1
1
A
V
IN
(COMP) = 1.3V
2
2
V
OL
Output "LOW" Voltage
V
IN
(COMP) = 1.1V
150
250
250
mV
I
O
(COMP) = 400 A
400
400
I
B
Input Bias Current
0
V
IN
(COMP)
5V
10
-30
30
-30
30
nA
-50
50
-50
50
GROUND PIN CURRENT
I
GND
Ground Pin Current
I
L
(Main Out) = 1 mA
170
250
250
A
(Note 15)
I
L
(Aux. Out) = 0.1 mA
280
280
I
L
(Main Out) = 50 mA
1.1
2
2
I
L
(Aux. Out) = 1 mA
2.5
2.5
I
L
(Main Out) = 100 mA
3
6
6
I
L
(Aux. Out) = 1 mA
8
8
I
L
(Main Out) = 250 mA
16
28
28
mA
I
L
(Aux. Out) = 1 mA
33
33
I
L
(Main Out) = 1 mA
3
6
6
I
L
(Aux. Out) = 50 mA
8
8
I
L
(Main Out) = 1 mA
6
8
8
I
L
(Aux. Out) = 75 mA
10
10
I
GND
Ground Pin Current
V
IN
= 4.5V
325
325
at Dropout (Note 15)
I
L
(Main Out) = 0.1 mA
270
350
350
I
L
(Aux. Out) = 0.1 mA
A
I
GND
Ground Pin Current
No Load on Either Output
120
180
180
at Shutdown (Note 15)
I
(SD IN
)
1 A
200
200
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the de-
vice outside of its rated operating conditions.
Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, T
J
(max), the junction-to-ambient thermal resistance,
J-A
,
and the ambient temperature, T
A
. The maximum allowable power dissipation at any ambient temperature is calculated using: P(max) =
.
Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. See Application Hints for
additional information on heat sinking and thermal resistance.
Note 3: When used in dual-supply systems where the regulator load is returned to a negative supply, the output voltage must be diode-clamped to ground.
Note 4: May exceed the input supply voltage.
Note 5: Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 6: Load regulation is measured at constant junction temperature using low duty cycle pulse testing. Two separate tests are performed, one for the range of 100
A to 1 mA and one for the 1 mA to 250 mA range. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
Note 7: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below the value measured with a 1V differential. At
very low values of programmed output voltage, the input voltage minimum of 2V (2.3V over temperature) must be observed.
Note 8: Thermal regulation is the change in output voltage at a time T after a change in power dissipation, excluding load or line regulation effects. Specifications
are for a 200 mA load pulse at V
IN
= 20V (3W pulse) for T = 10 ms on the Main regulator output. For the Auxiliary regulator output, specifications are for a 66 mA
load pulse at V
IN
= 20V (1W pulse) for T = 10 ms.
Note 9: Connect a 0.1 F capacitor from the output to the feedback pin.
Note 10: Load regulation is measured at constant junction temperature using low duty cycle pulse testing. Two separate tests are performed, one for the range of
100 A to 1 mA and one for the 1 mA to 75 mA range. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
Note 11: Dropout dectection comparator thresholds are expressed as changes in a 5V output. To express the threshold voltages in terms of a differential at the
Feedback terminal, divide by the error amplifier gain = V
OUT
/V
REF
.
www.national.com
5
PDF 
ZIP