100mA Low Dropout
Voltage Regulators
LP2950 / LP2951
FEATURES
5V, 3.3V, and 3.0V Versions at 100mA Output
Very Low Quiescent Current
Low Dropout Voltage
Extremely Tight Load and Line Regulation
Very Low Temperature Coefficient
Current and Thermal Limiting
Needs Only 1
F for Stability
LP2951 Versions Only
Error Flag Warns of Output Dropout
Logic-Controlled Electronic Shutdown
Output Programmable from 1.24 to 29V
APPLICATIONS
Battery Powered Systems
Cordless Telephones
Radio Control Systems
Portable / Palm Top / Notebook Computers
Portable Consumer Equipment
Portable Instrumentation
Avionics
SMPS Post-Regulator
Voltage Reference
Automotive Electronics
PRODUCT DESCRIPTION
The Calogic 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 features very low quiescent current and very low
dropout voltage (Typ. 50mV at light load and 380mV at 100mA).
This includes a tight initial tolerance of 0.5% typ., extremely
good load and line regulation 0.05% typ. and very low output
temperature coefficient, making the LP2950/LP2951 useful
as a low-power voltage reference.
The error flag output feature is used as power-on reset for
warning of a low output voltage, due to falling voltage input of
batteries. Another feature is the logic-compatible shutdown
input which enables the regulator to be switched on and off.
The LP2950 is offered in a 3-pin TO-92 package compatible
with other 5V, 3.0V, 3.3V regulators. The LP2951 is also available
in 8-pin plastic and SO-8.
The regulator output voltage may be pin-strapped for 5V, 3V
or 3.3 volts or programmed from 1.24 volt to 29 volts with an
external pair of resistors. Use of AS's design, processing and
testing techniques make our LP2950 and LP2951 superior
over similar products.
ORDERING INFORMATION
PART
PACKAGE
TEMPERATURE RANGE
LP2950ACN-X
TO-92 (3-Pin)
IND.
LP2950CN-X
TO-92 (3-Pin)
IND.
LP2951ACP-X
Plastic DIP (8-Pin)
IND.
LP2951CP-X
Plastic DIP (8-Pin)
IND.
LP2951ACS-X
Plastic SOIC (8-Pin)
IND.
LP2951CS-X
Plastic SOIC (8-Pin)
IND.
X = 3.0V, 3.3V or 5.0V
CORPORATION
PIN CONNECTIONS
1D-20
1
2
3
1. OUTPUT
2. GROUND
3. INPUT
TO-92
BOTTOM VIEW
GROUND
1
2
3
8
7
6
4
5
ERROR
LP2951
1D-19
8-PIN SURFACE MOUNT
5V OR 3.3V TAP
FEEDBACK
INPUT
SHUTDOWN
SENSE
OUTPUT
TOP VIEW
CALOGIC CORPORATION, 237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
ABSOLUTE MAXIMUM RATINGS
Power Dissipation . . . . . . . . . . . . . . . . . . . . . Internally Limited
Lead Temp. (Soldering, 5 Seconds) . . . . . . . . . . . . . . . 260
o
C
Storage Temperature Range . . . . . . . . . . . . . . . -65 to +150
o
C
Operating Junction Temperature Range
LP2951. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to +150
o
C
LP2950AC/LP2950C
LP2951AC/LP2951C . . . . . . . . . . . . . . . . . . . -40 to +125
o
C
Input Supply Voltage . . . . . . . . . . . . . . . . . . . . . . -0.3 to +30V
Feedback Input Voltage . . . . . . . . . . . . . . . . . . . . -1.5 to +30V
Shutdown Input Voltage. . . . . . . . . . . . . . . . . . . . -0.3 to +30V
Error Comparator Output . . . . . . . . . . . . . . . . . . . -0.3 to +30V
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2KV Min
LP2950 / LP2951
CORPORATION
CALOGIC CORPORATION, 237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
ELECTRICAL CHARACTERISTICS: V
S
= 15V, T
A
= 25
o
C, unless otherwise specified.
PARAMETER
LP2951
LP2950AC / LP2951AC LP2950C / LP2951C
UNITS
CONDITIONS
(Note 2)
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
3V VERSIONS
Output Voltage
2.985
2.964
3.0
3.015
3.036
2.985
2.970
2.964
3.0
3.0
3.0
3.015
3.030
3.036
2.970
2.955
2.940
3.0
3.0
3.0
3.030
3.045
3.060
V
V
V
T
J
= 25
o
C
-25
o
C
T
J
85
o
C
Full Operating Temperature
Output Voltage
2.955
3.0
3.045
2.958
3.0
3.042
2.928
3.0
3.072
V
100
A
I
L
100mA
T
J
T
JMAX
3.3V VERSIONS
Output Voltage
3.284
3.260
3.3
3.317
3.340
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
V
V
T
J
= 25
o
C
-25
o
C
T
J
85
o
C
Full Operating Temperature
Output Voltage
3.251
3.3
3.350
3.254
3.3
3.346
3.221
3.3
3.379
V
100
A
I
L
100mA
T
J
T
JMAX
5V VERSIONS
Output Voltage
4.975
4.94
5.0
5.025
5.06
4.975
4.95
4.94
5.0
5.0
5.0
5.025
5.050
5.06
4.95
4.925
4.90
5.0
5.0
5.0
5.05
5.075
5.10
V
V
V
T
J
= 25
o
C
-25
o
C
T
J
85
o
C
Full Operating Temperature
Output Voltage
4.925
5.0
5.075
4.93
5.0
5.07
4.88
5.0
5.12
V
100
A
I
L
100mA
T
J
T
JMAX
ALL VOLTAGE OPTIONS
Output Voltage
Temperature Coefficient
20
120
20
50
ppm/
o
C
(Note 1)
Line Regulation (Note 3)
0.03
0.1
0.03
0.1
0.04
0.2
%
6V
V
IN
30V (Note 4)
Load Regulation (Note 3)
0.04
0.1
0.04
0.1
0.1
0.2
%
100
A
I
L
100mA
Dropout Voltage
(Note 5)
50
380
80
450
50
380
80
450
50
380
80
450
mV
mV
I
L
= 100
A
I
L
= 100mA
Ground Current
150
8
170
12
150
8
170
12
150
8
170
12
A
mA
I
L
= 100
A
I
L
= 100mA
Current Limit
130
200
130
200
130
200
mA
V
OUT
= 0
Thermal Regulation
0.05
0.2
0.05
0.2
0.05
0.2
%/W
Output Noise,
10Hz to 100KHz
430
160
100
430
160
100
430
160
100
Vrms
Vrms
Vrms
C
L
= 1
F
C
L
= 200
F
C
L
= 13.3
F
(Bypass = 0.01
F pins 7 to 1 (LP2951))
8-PIN VERSIONS ONLY
LP2951
LP2951AC
LP2951C
Reference Voltage
1.22
1.235
1.25
1.22
1.235
1.25
1.21
1.235
1.26
V
Reference Voltage
1.19
1.27
1.19
1.27
1.185
1.285
V
Over Temperature (Note 6)
Feedback Pin Bias Current
40
60
40
60
40
60
nA
Reference Voltage
Temperature Coefficient
20
20
50
ppm/
o
C
(Note 7)
Feedback Pin Bias Current
Temperature Coefficient
0.1
0.1
0.1
nA/
o
C
LP2950 / LP2951
CORPORATION
BLOCK DIAGRAM
ERROR DETECTION
COMPARATOR
1D-21
1
F
REFERENCE
1.23V
UNREGULATED DC
ERROR
AMPLIFIER
60mV
+
+
TO CMOS OR
TTL
330k
FROM
CMOS
OR TTL
+
+
5V @ 100mA
MAX
60k
LP2950 AND LP2951 BLOCK DIAGRAM
180k
8
1
7
SENSE
6
2
4
5
5V TAP
ERROR
GROUND
INPUT
OUTPUT
FEEDBACK
SHUTDOWN
3
+
+
CALOGIC CORPORATION, 237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
ELECTRICAL CHARACTERISTICS (continued)
PARAMETER
LP2951
LP2950AC / LP2951AC LP2950C / LP2951C
UNITS
CONDITIONS
(Note 2)
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
ERROR COMPARATOR
Output Leakage Current
0.01
1
0.01
1
0.01
1
A
V
OH
= 30V
Output Low Voltage
150
250
150
250
150
250
mV
V
IN
= 4.5V, I
OL
= 400
A
Upper Threshold Voltage
40
60
40
60
40
60
mV
(Note 7)
Lower Threshold Voltage
75
95
75
95
75
95
mV
(Note 7)
Hysteresis
15
15
15
mV
(Note 7)
SHUTDOWN INPUT
Input Logic Voltage
2
1.3
0.6
2
1.3
0.7
2
1.3
0.7
V
V
Low (Regulator ON)
High (Regulator OFF)
Shutdown Pin
Input Current
30
675
50
800
30
675
50
800
30
675
50
800
A
A
V
S
= 2.4V
V
S
= 30V
Regulator Output Current
in Shutdown
3
10
3
10
3
10
A
(Note 9)
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 T
J
= 25
o
C, V
IN
= 6V, I
L
=100
A and C
L
= 1
F. 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 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 150
o
C for I
L
= 1mA. For I
L
= 100
A and T
J
= 125
o
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 100mV 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 input account.
Note 6: V
REF
V
OUT
(V
IN
- 1V), 2.3
V
IN
30V, 100
A
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 nominal 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
=
(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 95mV x
5V/1.235 = 384mV. 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.
APPLICATION HINTS
EXTERNAL CAPACITORS
The stability of the LP2950/LP2951 requires a 1.0
F or
greater capacitor between output and ground. Oscillation
could occur without this capacitor. Most types of tantalum
or aluminum electrolytic are acceptable. For operations
below -25
o
C a solid tantalum is recommended since the
many aluminum types have electrolytes that freeze at about
-30
o
C. The ESR of about 5
or less and resonant
frequency about 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 currents below 10mA the value of
the capacitor can be reduced to 0.33
F and 0.1
F 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
F or greater must be used for the
condition of 100mA load at 1.23V output.
The LP2950, 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 circuits. When
setting the output voltage of the LP2951 version with
external resistors, a minimum load of 1
A 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 1
A tantalum or aluminum electrolytic capacitor
should be placed from the input to the ground.
Instability can occur if there is a 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 eliminated by
adding a 100pF capacitor between output and feedback
and increasing the output capacitor to at least 3.3
F.
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 occurs at approximately 60mV 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 V
OUT
= 4.75). Since the LP2951's
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 pullup 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 400
A, this value adds to
battery drain in a low battery condition. Suggested values
range from 100K to 1M
. 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 equation below for the programming of the output
voltage:
V
OUT
= V
REF
(1 + R
1
\R
2
) + I
FB
R
1
The V
REF
is 1.235 and I
FB
is the feedback bias current,
nominally -20nA. The minimum recommended load current of
1
A forces an upper limit of 1.2M
on value of R
2
. If no load
is presented the I
FB
produces an error of typically 2% in V
OUT
which may be eliminated at room temperature by trimming R
1
.
To improve the accuracy choose the value of R2 = 100k this
reduces the error by 0.17% and increases the resistor
program current by 12
A. Since the LP2951 typically draws
60
A 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 lead 3 of LP2950, but is
relatively inefficient, as increasing the capacitor from 1
F to
220
F only decreases the noise from 430
V to 160
Vrms for
a 100kHz bandwidth at 5V output.
Noise could also be reduced fourfold by a bypass capacitor
across R
1
, since it reduces the high frequency gain from 4 to
unity.
C
BYPASS
1/2
R
1
200Hz
or choose 0.01
F. When doing this, the output capacitor must
be increased to 3.3
F to maintain stability. These changes
reduce the output noise from 430
V to 100
Vrms 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 voltages.
LP2950 / LP2951
CORPORATION
CALOGIC CORPORATION, 237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
LP2950 / LP2951
CORPORATION
CALOGIC CORPORATION, 237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
LOAD CURRENT (mA)
10
0.01
0.1
100
1D-22
QUIESCENT CURRENT
GROUND PIN CURRENT (mA)
0.1
1
1.0
10
INPUT VOLTAGE (VOLTS)
250
0
0
10
1D-24
INPUT CURRENT
INPUT CURRENT (
A)
5
6
7
8
4
9
3
2
1
25
50
75
100
125
150
175
200
225
=
R
L
= 50k
R
L
5V OUTPUT
INPUT VOLTAGE (VOLTS)
6
0
3
0
6
1D-23
DROPOUT
CHARACTERISTICS
3
OUTPUT VOLTAGE (VOLTS)
1
2
4
5
1
2
4
5
R
L
= 50k
R
L
= 50
5V OUTPUT
TYPICAL PERFORMANCE CHARACTERISTICS
INPUT VOLTAGE (VOLTS)
120
0
0
10
1D-25
INPUT CURRENT
INPUT CURRENT (mA)
5
6
7
8
4
9
3
2
1
60
20
40
80
100
10
70
30
50
90
110
R
L
= 50
5V OUTPUT
INPUT VOLTAGE (VOLTS)
160
0
0
8
1D-27
QUIESCENT CURRENT
QUIESCENT CURRENT (
A)
1
2
3
4
5
6
7
20
40
60
100
120
140
80
5V OUTPUT
I
L
= 1mA
I
L
= 0
TEMPERATURE (C)
5.06
4.94
5.0
75
150
1D-26
OUTPUT VOLTAGE vs
TEMPERATURE OF 3
REPRESENTATIVE UNITS
OUTPUT VOLTAGE (V)
4.96
4.98
5.02
5.04
50 25 0
25 50 75 100 125
5V OUTPUT
0.2%
TEMPERATURE (C)
170
100
75
150
1D-28
SHORT CIRCUIT CURRENT
SHORT CIRCUIT CURRENT (mA)
50 25 0
25 50 75 100 125
160
150
140
130
120
110
OUTPUT CURRENT
500
0
100
A
100mA
1D-30
DROPOUT VOLTAGE
DROPOUT VOLTAGE (mV)
400
300
200
100
10mA
1mA
T
J
= 25C
TEMPERATURE (C)
600
0
75
150
1D-29
DROPOUT VOLTAGE
DROPOUT VOLTAGE (mV)
50 25 0
25 50 75 100 125
500
400
300
100
50
I
L
= 100mA
I
L
= 100
A
TEMPERATURE (C)
120
50
75
150
1D-31
QUIESCENT CURRENT
QUIESCENT CURRENT (
A)
50 25 0
25 50 75 100 125
110
100
90
80
70
60
5V OUTPUT
V
IN
= 6V
I
L
= 100
A
INPUT VOLTAGE (V)
8
0
0
8
1D-33
QUIESCENT CURRENT
QUIESCENT CURRENT (mA)
1
2
3
4
5
6
7
1
2
3
5
6
7
4
I
L
= 100mA
5V OUTPUT
TEMPERATURE (C)
10
7
75
150
1D-32
QUIESCENT CURRENT
QUIESCENT CURRENT (mA)
50 25 0
25 50 75 100 125
9
8
5V OUTPUT
V
IN
= 6V
I
L
= 100mA
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