Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
1
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
LP2950/LP2951
100mA Low Dropout Voltage Regulators
FEATURES APPLICATIONS
• 5.0V and 3.3V Versions at 100mA Output • Battery Powered Systems
•Very Low Quiescent Current • Cordless Telephones
•Low Dropout Voltage: 380mV at 100mA • Radio Control Systems
• Extremely Tight Load and Line Regulation • Portable/Palm Top/Notebook Computers
•Very Low Temperature Coefficient • Portable Consumer Equipment
•Current & Thermal Limiting • Portable Instrumentation
•Need Only 1 µF for Stability • Avionics
• Offered in TO-92 (LP2950) & SOIC (LP2951) • SMPS Post-Regulator
• Direct Replacement For LP2950/LP2951 • Voltage Reference
• Automotive Electronics
LP2951 versions only
• Error Flag Warns of Output Dropout
• Logic-Controlled Electronic Shutdown
• Output Programmable From 1.24 to 29V
PRODUCT DESCRIPTION
The LP2950 and LP2951 are low power voltage regulators. These devices are an excellent choice for use in battery-powered
applications such as cordless telephones, radio control systems, and portable computers. The LP2950 and LP2951 feature low
quiescent current and low dropout voltage (typ. 50mV at light load and 380 mV at 100mA). This includes a tight initial tolerance
(0.5% typ.), extremely good load and line regulation (0.05% typ.), and very low output temperature coefficient (20 ppm/¡C typ.),
making the LP2950/LP2951 useful as a low-power voltage reference.
The error flag output feature is used as a power-on reset for warning of a low output voltage, due to a falling input voltage. The logic-
compatible shutdown feature enables the regulator to be switched ON and OFF. The LP2950 is offered in a 3-pin TO-92 package
compatible with other 5V, 3.3V regulators. The LP2951 is available in an 8-lead SOIC package.
Block diagram of LP2951
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
2
LP2950/51
ABSOLUTE MAXIMUM RATINGS
Power Dissipation.....................................Internally Limited Feedback Input Voltage................................................ -1.5V to +30V
Lead Temp. (Soldering, 5 Seconds)............................ 260¡C Shutdown Input Voltage............................................... -0.3V to +30V
Storage Temperature Range ......................... -65¡ to +150¡C Error Comparator Output ............................................. -0.3V to +30V
Operating Junction Temperature Range -40C to +125C ESD Rating .........................................................................2kV Min
Input Supply Voltage..................................... -0.3V to +30V
ELECTRICAL CHARACTERISTICS VIN=6V, IO=100µA, COUT=1µF (Note 2) TA=25C, unless otherwise noted.
PARAMETER CONDITIONS
LP2950AC
LP2951AC
Min. Typ. Max.
LP2950C
LP2951C
Min. Typ. Max. UNITS
3.3 V Versions
Output Voltage TJ = 25¡C
-25¡C ≤TJ ≤85¡C
Full Operating Temperature
3.284
3.267
3.260
3.3
3.3
3.3
3.317
3.333
3.340
3.267
3.251
3.234
3.3
3.3
3.3
3.333
3.350
3.366
V
Output Voltage 100 µA ≤IL ≤100 mA
TJ ≤TJMAX
3.254 3.3 3.346 3.221 3.3 3.379 V
5 V Versions
Output Voltage TJ = 25¡C
-25¡C ≤TJ ≤85¡C
Full Operating Temperature
4.975
4.950
4.940
5.0
5.0
5.0
5.025
5.050
5.060
4.950
4.925
4.900
5.0
5.0
5.0
5.050
5.075
5.100
V
Output Voltage 100 µA ≤IL ≤100 mA
TJ ≤TJMAX
4.925 5.0 5.075 4.880 5.0 5.120 V
All Voltage Options
Output Voltage
Temperature Coefficient (Note 1)
20 120 50 150 ppm/¡C
Line Regulation (Note 3) 6V ≤VIN ≤30V (Note 4) 0.03 0.1 0.04 0.2 %
Load Regulation (Note 3) 100 µA ≤IL ≤ 100 mA 0.04 0.1 0.1 0.2 %
Dropout Voltage
(Note 5)
IL = 100 µA
IL = 100 mA
50
380
80
450
50
380
80
450
mV
mV
Ground Current IL = 100 µA
IL = 100 mA
150
8
170
12
150
8
170
12 µA
mA
Current Limit VOUT = 0 150 200 150 200 mA
Thermal Regulation 0.05 0.2 0.05 0.2 %/W
Output Noise, CL = 1µF 430 430 µV rms
10Hz to 100KHz CL = 200 µF 160 160 µV rms
CL = 3.3 µF, Bypass = 0.01µF
from Pin 7 to Pin 1 (LP2951)
100 100 µV rms
8-Pin Versions only LP2951AC LP2951C
Reference Voltage 1.220 1.235 1.250 1.210 1.235 1.260 V
Reference Voltage Over Temperature (Note 6) 1.190 1.270 1.185 1.285 V
Feedback Pin Bias
Current
40 60 40 60 nA
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
3
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 VOH = 30V 0.01 1 0.01 1 µA
Output Low Voltage VIN = 4.5V
IOL = 400µA
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
Note 1: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range.
Note 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.
Note 3: 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 under the specification for thermal regulation.
Note 4: Line regulation for the LP2951 is tested at IL = 1mA. For IL = 100 µA 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.
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 taken into account.
Note 6: VREF ≤VOUT ≤ (VIN - 1V), 2.3 ≤VIN≤30V, 100µA≤IL≤ 100mA, TJ ≤ TJMAX.
Note 7: 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 95 mV x 5V/1.235 = 384 mV. Thresholds remain constant as a percent of VOUT as VOUT
is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
Note 8: VSHUTDOWN ≥ 2V, VIN ≤ 30V, VOUT =0, Feedback pin tied to 5V Tap.
Note 9: All typical values are not guaranteed. The value could vary from lot to lot.
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
4
Input Current
INPUT CURRENT (µA)
75
0
010
INPUT VOLTAGE (VOLTS)
R
L
= 50kΩ
25
50
100
125
150
175
200
225
250
123
R
L
=
8
Dropout Characteristics
OUTPUT V OLT A GE (VOLTS)
00
INPUT V OLT A GE (VOLTS)
123 456
1
2
3
4
5
6
R
L
=50kΩ
R
L
=50kΩ
456789
LOAD CURRENT (mA)
Quiescent Current
GROUND PIN CURRENT (mA)
10
1
0.1
0.01
0.1 1 10 100
Ground Current
GROUND CURRENT (µA)
320
280
0
INPUT V OLT A GE (VOLTS)
240
80
40
012345678
120
160
200
I
L
= 1mA
I
L
= 0
INPUT V OLT A GE (VOLTS)
Input Current
INPUT CURRENT (mA)
160
150
140
130
70
50
0
120
110
100
90
80
60
40
30
20
10
0
12345678910
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 (µA)
V
IN
=6V
I
L
=100uA
Ground Current
16
14
12
012345678
INPUT V OLT A GE
GROUND CURRENT (mA)
10
8
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 CURRENT (mA)
V
IN
= 6V
I
L
= 100mA
LP2950/ LP2951
TYPICAL PERFORMANCE CHARACTERISTIC
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
5
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 T ransient 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
= 1µF
I
L
= 1mA
V
OUT
= 5V
Error Comparator Output
COMPARATOR OUTPUT (V)
8
6
0
INPUT V OLT A GE (V)
4
2
0
-2
12345
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
= 100µA
I
O
= 1mA
V
OUT
= 5V
C
L
= 1µF
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
= 100µA
I
L
= 0
C
L
= 1µF
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 V OLT AGE (mV)
500
100
0
I
L
= 100mA
I
L
= 100µA
~
~
Drop-Out Voltage
T
J
= 25ºC
OUTPUT CURRENT
DROP-OUT V OLT AGE (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
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
6
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
FEEDBA CK V OLTAGE (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 T ransient Response
250
100
-50
100
012345
TIME (ms)
LOAD OUTPUT VOLTAGE
CURRENT CHANGE (mV)
µA
~
~
mA
-100
0
50
150
200
C
L
= 1µF
V
OUT
= 5V
100
Load T ransient Response
80
20
-40
100
048121620
TIME (ms)
LOAD OUTPUT VOLTAGE
CURRENT CHANGE (mV)
µA
100
-60
-20
0
40
60
µA
C
L
= 10µF
V
OUT
= 5V
~
~
LP2950 Maxium Rated Output
OUTPUT CURRENT (mA)
120
80
0
010 20 30
INPUT V OLT A GE (V)
25155
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 V OLT A GE (V)
80
20
0
510 15 202530
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 T ransient
7
6
4
-100 0100 200 300 400 500 600 700
TIME (us)
SHUTDOWN OUTPUT
PINOUT V OLT A GE (V) VOLT AGE (V)
3
2
1
0
2
-2
0
5
OUT
= 5V
V
IN
= 8V
I
L
= 10mA
V
LP2951 Divider Resistance
PIN 2 TO PIN 4 RESISTANCE (kΩ)
400
200
100
0
-75 0 75 150
TEMPERATURE (ºC)
-50 -25 25 50 100 125
300
C
L
= 1µF
C
L
= 10µF
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
7
Shutdown Threshold Voltage
SHUTDOWN THRESHOLD VOLTAGE (V)
1.8
1.6
1.0
-75
TEMPERATURE (¼C)
1.4
1.2
0.8
0.6
-50 -25 0 25 50 75 100 125 150
Thermal Response
POWER OUTPUT VOLTAGE
DISSIPATION (W) CHANGE (mV)
4
2
1
0
TIME (µs)
0
-2
0
-1
10 20 30 40 50
5
1.25W
~
~
Output Noise
VOLTAGE NOISE
SPECTRAL DENSITY (µV/Hz)
3.5
2.5
2.0
0.0
10
2
10
3
10
4
10
5
FREQUENCY (Hz), C
BYP
=0.1uF
3.0
1.5
1.0
0.5
C = 3.3µF
L
Ripple Rejection
RIPPLE REJECTION (dB)
80
60
40
10
10
1
10
3
10
4
10
6
FREQUENCY (Hz)
I
L
= 50µA
I
L
= 100mA
C
L
= 1µF
V
IN
= 6V
V
OUT
= 5V
70
50
30
20
10
2
10
5
Line Regulation
OUTPUT VOLTAGE CHANGE (mV)
30
25
20
10
5
INPUT VOLTAGE (V)
15
10
5
0
5
0
-5
-10
10 15 20 25 30
~
~
I
L
= 100µA
I
L
= 1mA
T
J
= 150 ¼C
T
J
= 125 ¼C I
L
= 100µA
C = 0.1µF
BYP
C
L
= 220µF
I
L
= 100mA
C
L
= 1µF
LP2950/LP2951
TYPICAL APPLICATIONS
9
+
+
+
+
4.75V
OUTPUT
VOLTAGE
ERROR*
_______
INPUT
VOLTAGE 1.3V
5.0V
* See Application Info.
LP2950/51
APPLICATION HINTS
EXTERNAL CAPACITORS
The stability of the LP2950/LP2951 requires a 1.0µF or greater
capacitor between output and ground. Oscillation could occur without
this capacitor. Most types of tantalum or aluminum electrolytic works
fine here. For operations below -25°C solid tantalum is recommended
since the many aluminum types have electrolytes that freeze at about
-30°C. The ESR of about 5Ω or less and resonant frequency above
500kHz are the most important parameters in the value of the
capacitor. The capacitors value may be increased without limit.
At lower values of output current, less output capacitance is required
for stability. For the currents below 10mA the value of the capacitor
can be reduced to 0.33µF and 0.1µF for 1mA. More output
capacitance is needed for the 8-pin version at voltages below 5V
since it runs the error amplifier at lower gain. At worst case 3.3 µF or
greater must be used for the condition of 100mA load at 1.23V
output.
The LP2950/51 unlike other low dropout regulators will remain
stable and in regulation with no load in addition to the internal
voltage divider. This feature is especially important in applications
like CMOS RAM keep-alive. When setting the output voltage of the
LP2950/51 version with external resistors, a minimum load of 1µA is
recommended
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 then a 1µA tantalum
or aluminum electrolytic capacitor should be placed from the input to
the ground.
Instability can occur if there is stray capacitance to the LP2951
feedback terminal (pin 7). This could cause more problems when
using a higher value of external resistors to set the output voltage.
This problem can be fixed by adding a 100pF capacitor between
output and feedback and increasing the output capacitor to at least 3.3
µF.
\
ERROR DETECTION COMPARATOR OUTPUT
The Comparator produces a logic low output whenever the LP2951
output falls out of regulation by more than around 5%. This is around
60 mV offset divided by the 1.235 reference voltage. This trip level
remains 5% below normal regardless of the programmed output
voltage of the regulator.
Figure 1 shows the timing diagram depicting the ERROR signal and
the regulator output voltage as the LP2951 input is ramped up and
down. The ERROR signal becomes low at around 1.3V input, and
goes high around 5V input (input voltage at which VOUT = 4.75).
Since the LP2951Õs dropout voltage is load dependent, the input
voltage trip point (around 5V) will vary with the load current. The
output voltage trip point (approx. 4.75V) does not vary with load.
The error comparator has an open-collector output, which requires an
external pull-up resistor. Depending on the system requirements the
resistor may be returned to 5V output or other supply voltage. In
determining the value of this resistor, note that the output is rated to
sink 400µA, this value adds to battery drain in a low battery
condition. Suggested values range from 100K to 1MΩ. If the output
is unused this resistor is not required.
PROGRAMMING THE OUTPUT VOLTAGE OF 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). Also, it may be programmed for any output
voltage between its 1.235V reference and its 30V maximum rating .
As seen in Figure 2, an external pair of resistors is required. Refer to
the below equation for the programming of the output voltage:
VOUT = VREF × (1 + R1/R2)+ IFBR1
The VREF is 1.235 and IFB is the feedback bias current, nominally -
20nA. The minimum recommended load current of 1 µA forces an
upper limit of 1.2MΩ on value of R2. If no load is presented the IFB
produces an error of typically 2% in VOUT which may be eliminated
at room temperature by trimming R1. To improve the accuracy
choose the value of R2 = 100k this reduces the error by 0.17% and
increases the resistor program current by 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
It may be an advantage to reduce the AC noise present at the output.
One way is to reduce the regulator bandwidth by increasing the size
of the output capacitor. This is the only way that noise can be reduced
on the 3 lead LP2950 but is relatively inefficient, as increasing the
capacitor from 1µF to 220 µF only decreases the noise from 430µV
to 160µVRMS for a 100kHz bandwidth at 5V output. Noise could also
be reduced fourfold by a bypass capacitor across R1, since it reduces
the high frequency gain from 4 to unity. Pick
CBYPASS ≅ 1 / 2πR1 × 200 Hz
or choose 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 a 100kHz 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
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
8
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
9
LP2950/LP2951
TYPICAL APPLICATIONS
100K
OUTPUT
ERROR
ERROR
______
SD
V
OUT
GND FB
+V
IN
+V
IN
1.23V
1.2 to 30V
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
Figure 2. Adjustable Regulator
Figure 3. Latch Off When Error Flag Occurs Figure 4. Wide Input voltage Range Current Limiter
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
10
LP2950/LP2951
TYPICAL APPLICATIONS (continued)
100kΩ
SENSE
SD
V
OUT
GND
+V
IN
3
8
1
1µF
+
4
400
kΩ
120kΩ1.5kΩ
6V
SEALED
LEAD-
ACID
BATTERY
SOURCE
FB
FOR 5.5 V
+
1N457
2
20kΩ
NI-CAD
BACKUP
BATTERY
MEMORY V+
MAIN V+
SPX385
LP2951
GND
4
3
5
8
2
1
7
6
SD
TAP
FB
+V
IN
SENSE
V
OUT
ERROR
______
RESET
100k
100k
100k
1k
100k
10k
20k
1k
39k
39k
C3
C1
C2
C4
1%
1%
1%
1%
6V
LEAD-
ACID
BATTERY
R
3
<6.2V**
<5.8V**
<6.0V**
-
+
+
+
+
-
-
-
Ω
..
Ω
..
Ω
..
Ω
..
Ω
..
Ω
..
Ω
..
Ω
..
Ω
..
Ω
..
+V
OUT
= 5V
1uF
+
* OPTIONAL LATCH OFF WHEN DROPOUT OCCURS. ADJUST R3 FOR C2 SWITCHING WHEN
V
IN
IS 6.0V
* OUTPUTS GO LOW WHEN V
IN
DROPS BELOW DESGNATED THRESHHOLDS
LP2951
Figure 5. Low Battery disconnect
Figure 6. Regulator with State-of Charge Indicator
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
11
EXTERNAL CIRCUIT
PROTECTED FROM
O VER 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
LP2950/LP2951
TYPICAL APPLICATIONS (continued)
Figure 7. System Over Temperature Protection
Figure 8. Open Circuit Detector for 4mA to 20mA Current
Loop
Figure 9. 300mA Regulator with 0.75V
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
12
LP2950/LP2951
SCHEMATIC DIAGRAM
Rev. 8/6/01 LP2950/51 100mA Low Dropout Voltage Regulators ©Copyright 2001 Sipex Corporation
13
LP2950/LP2951
PACKAGE DIAGRAM
TO-92 (N)
8-Pin Surface Mount (S)
ALPHA
AS293
0
1
LP2951 Top View
2
3
45
6
7
8
OUTPUT
SENSE
SHUTDOWN
GROUND
INPUT
FEEDBACK
5V or 3.3V Output
ERROR
LP2950 Bottom View
13
2
V
IN
GROUND
V
OUT
ORDERING INFORMATION
Ordering No. Accuracy Output Voltage Packages
LP2950ACN-3.3 0.5% 3.3V 3 lead TO-92
LP2950ACN-5.0 0.5% 5.0V 3 lead TO-92
LP2950CN-3.3 1% 3.3V 3 lead TO-92
LP2950CN-5.0 1% 5.0V 3 lead TO-92
LP2951ACS-3.3 0.5% 3.3V 8 Lead SOIC
LP2951ACS-5.0 0.5% 5.0V 8 Lead SOIC
LP2951CS-3.3 1% 3.3V 8 Lead SOIC
LP2951CS-5.0 1% 5.0V 8 Lead SOIC
SIGNAL PROCESSING EXCELLENCE
Sipex Corporation
Headquarters and Main Offices:
22 Linnell Circle
Billerica, MA 01821
TEL: (978) 667-8700
FAX: (978) 670-9001
e-mail: sales@sipex.com
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 935-7600
FAX: (408) 934-7500
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described hereing; neither does it
convey any license under its patent rights nor the rights of others.
Corporation
