100mA Low Dropout
Voltage Regulators
CORPORATION
LP2950 / LP2951
FEATURES
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
LP2950ACN-X
LP2950CN-X
LP2951ACP-X
LP2951CP-X
LP2951ACS-X
LP2951CS-X
PACKAGE
TEMPERATURE RANGE
IND.
IND.
IND.
IND.
IND.
IND.
TO-92 (3-Pin)
TO-92 (3-Pin)
Plastic DIP (8-Pin)
Plastic DIP (8-Pin)
Plastic SOIC (8-Pin)
Plastic SOIC (8-Pin)
•
5V, 3.3V, and 3.0V Versions at 100mA Output
•
Very Low Quiescent Current
•
Low Dropout Voltage and Line Regulation
•
Extremely Tight Load
•
Very Low Temperature Coefficient
and Thermal Limiting
•
CurrentOnly 1µF for Stability
Needs
•
•
•
•
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
X = 3.0V, 3.3V or 5.0V
PIN CONNECTIONS
8-PIN SURFACE MOUNT
OUTPUT
SENSE
SHUTDOWN
GROUND
1
2
LP2951
3
4
TOP VIEW
6
5
5V OR 3.3V TAP
ERROR
8
7
INPUT
FEEDBACK
TO-92
1
2
3
1. OUTPUT
2. GROUND
3. INPUT
BOTTOM VIEW
1D-19
1D-20
CALOGIC CORPORATION,
237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
LP2950 / LP2951
CORPORATION
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
ELECTRICAL CHARACTERISTICS:
V
S
= 15V, T
A
= 25
o
C, unless otherwise specified.
PARAMETER
3V VERSIONS
2.985
Output Voltage
2.964
Output Voltage
3.3V VERSIONS
3.284
Output Voltage
3.260
Output Voltage
5V VERSIONS
4.975
Output Voltage
4.94
Output Voltage
ALL VOLTAGE OPTIONS
Output Voltage
Temperature Coefficient
Line Regulation (Note 3)
Load Regulation (Note 3)
Dropout Voltage
(Note 5)
Ground Current
Current Limit
Thermal Regulation
Output Noise,
10Hz to 100KHz
8-PIN VERSIONS ONLY
Reference Voltage
Reference Voltage
Feedback Pin Bias Current
Reference Voltage
Temperature Coefficient
Feedback Pin Bias Current
Temperature Coefficient
1.22
1.19
40
20
0.1
20
0.03
0.04
50
380
150
8
130
0.05
430
160
100
LP2951
1.235
1.25
1.27
60
1.22
1.19
40
20
0.1
120
0.1
0.1
80
450
170
12
200
0.2
20
0.03
0.04
50
380
150
8
130
0.05
430
160
100
LP2951AC
1.235
1.25
1.27
60
1.21
1.185
40
50
0.1
0.1
0.1
80
450
170
12
200
0.2
50
0.04
0.1
50
380
150
8
130
0.05
430
160
100
LP2951C
1.235
1.26
1.285
60
V
V
nA
ppm/
o
C
nA/
o
C
(Note 7)
Over Temperature (Note 6)
0.2
0.2
80
450
170
12
200
0.2
ppm/
o
C
%
%
mV
mV
µA
mA
mA
%/W
µVrms
µVrms
µVrms
C
L
= 1µF
C
L
= 200µF
C
L
= 13.3µF
(Bypass = 0.01µF pins 7 to 1 (LP2951))
LP2951
MIN
TYP
3.0
MAX
3.015
3.036
3.0
3.045
LP2950AC / LP2951AC LP2950C / LP2951C
MIN
2.985
2.970
2.964
2.958
TYP
3.0
3.0
3.0
3.0
MAX
3.015
3.030
3.036
3.042
MIN
2.970
2.955
2.940
2.928
TYP
3.0
3.0
3.0
3.0
MAX
3.030
3.045
3.060
3.072
UNITS
CONDITIONS
(Note 2)
T
J
= 25
o
C
-25
o
C
≤
T
J
≤
85
o
C
Full Operating Temperature
100µA
≤
I
L
≤
100mA
T
J
≤T
JMAX
T
J
= 25
o
C
-25
o
C
≤
T
J
≤
85
o
C
Full Operating Temperature
100µA
≤
I
L
≤
100mA
T
J
≤T
JMAX
T
J
= 25
o
C
-25
o
C
≤
T
J
≤
85
o
C
Full Operating Temperature
100µA
≤
I
L
≤
100mA
T
J
≤
T
JMAX
V
V
V
V
2.955
3.3
3.317
3.340
3.284
3.267
3.260
3.254
3.3
3.3
3.3
3.3
3.317
3.333
3.340
3.346
3.267
3.251
3.234
3.221
3.3
3.3
3.3
3.3
3.333
3.350
3.366
3.379
V
V
V
V
3.251
3.3
3.350
5.0
5.025
5.06
4.975
4.95
4.94
4.93
5.0
5.0
5.0
5.0
5.025
5.050
5.06
5.07
4.95
4.925
4.90
4.88
5.0
5.0
5.0
5.0
5.05
5.075
5.10
5.12
V
V
V
V
4.925
5.0
5.075
(Note 1)
6V
≤
V
IN
≤
30V (Note 4)
100µA
≤
I
L
≤
100mA
I
L
= 100µA
I
L
= 100mA
I
L
= 100µA
I
L
= 100mA
V
OUT
= 0
CALOGIC CORPORATION,
237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
LP2950 / LP2951
CORPORATION
ELECTRICAL CHARACTERISTICS
(continued)
PARAMETER
ERROR COMPARATOR
Output Leakage Current
Output Low Voltage
Upper Threshold Voltage
Lower Threshold Voltage
Hysteresis
SHUTDOWN INPUT
Input Logic Voltage
Shutdown Pin
Input Current
Regulator Output Current
in Shutdown
LP2951
MIN
TYP
MAX
0.01
150
60
75
15
1.3
2
30
675
3
50
800
10
1
250
40
95
LP2950AC / LP2951AC LP2950C / LP2951C
MIN
TYP
MAX
MIN
TYP MAX
0.01
150
60
75
15
1.3
2
30
675
3
50
800
10
1
250
40
95
0.01
150
60
75
15
1.3
2
30
675
3
50
800
10
1
250
95
UNITS
µA
mV
mV
mV
mV
V
V
µA
µA
µA
CONDITIONS
(Note 2)
V
OH
= 30V
V
IN
= 4.5V, I
OL
= 400µA
(Note 7)
(Note 7)
(Note 7)
Low (Regulator ON)
High (Regulator OFF)
V
S
= 2.4V
V
S
= 30V
(Note 9)
40
0.6
0.7
0.7
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
=100µA 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 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
= 100µA 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, 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 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.
BLOCK DIAGRAM
UNREGULATED DC
7
FEEDBACK
8
INPUT
1
OUTPUT
2
SENSE
+
3
FROM
CMOS
OR TTL
SHUTDOWN
+
60mV
+
1.23V
REFERENCE
GROUND
LP2950 AND LP2951 BLOCK DIAGRAM
1D-21
+
5V @ 100mA
MAX
–
ERROR
AMPLIFIER
180k
Ω
6
5V TAP
330k
Ω
+
1µF
TO CMOS OR
TTL
60kΩ
+
–
ERROR DETECTION
COMPARATOR
5
ERROR
4
CALOGIC CORPORATION,
237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
LP2950 / LP2951
CORPORATION
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 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 5Ω 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.
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 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 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
1µA forces an upper limit of 1.2MΩ 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 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 lead 3 of LP2950, but is
relatively inefficient, as increasing the capacitor from 1µF to
220µF 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 R
1
, since it reduces the high frequency gain from 4 to
unity.
C
BYPASS
≅
1/2πR
1
×
200Hz
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 voltages.
•
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 0.33µF 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 3.3µF 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 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.
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 3.3µF.
•
Instability
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.
CALOGIC CORPORATION,
237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
LP2950 / LP2951
CORPORATION
TYPICAL PERFORMANCE CHARACTERISTICS
QUIESCENT CURRENT
OUTPUT VOLTAGE (VOLTS)
10
GROUND PIN CURRENT (mA)
6
5
DROPOUT
CHARACTERISTICS
5V OUTPUT
INPUT CURRENT (µA)
250
225
200
175
150
125
100
75
50
25
INPUT CURRENT
5V OUTPUT
R
L
= 50kΩ
1
4
R
L
= 50kΩ
3
R
L
= 50Ω
2
1
0
R
L
=
0.1
∞
0.01
0.1
0
0
1
2
3
4
5
INPUT VOLTAGE (VOLTS)
6
1D-23
1.0
10
LOAD CURRENT (mA)
100
1D-22
0
1
2 3 4 5 6 7 8 9 10
INPUT VOLTAGE (VOLTS)
1D-24
120
5V OUTPUT
110
R
L
= 50Ω
100
90
80
70
60
50
40
30
20
10
0
0 1 2 3 4 5 6 7 8 9 10
INPUT VOLTAGE (VOLTS)
1D-25
INPUT CURRENT
5.06
5.04
5.02
5.0
4.98
4.96
OUTPUT VOLTAGE vs
TEMPERATURE OF 3
REPRESENTATIVE UNITS
5V OUTPUT
QUIESCENT CURRENT (µA)
160
140
120
100
80
60
40
20
0
0
QUIESCENT CURRENT
5V OUTPUT
OUTPUT VOLTAGE (V)
INPUT CURRENT (mA)
I
L
= 1mA
I
L
= 0
0.2%
4.94
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (˚C)
1D-26
1
2
3
4
5
6
7
INPUT VOLTAGE (VOLTS)
8
1D-27
170
SHORT CIRCUIT CURRENT (mA)
160
150
140
130
120
110
SHORT CIRCUIT CURRENT
DROPOUT VOLTAGE (mV)
600
500
400
300
100
50
DROPOUT VOLTAGE
DROPOUT VOLTAGE (mV)
500
DROPOUT VOLTAGE
400
I
L
= 100mA
300
200
T
J
= 25˚C
100
I
L
= 100µA
100
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (˚C)
1D-28
0
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (˚C)
1D-29
0
100µA
1mA
10mA
OUTPUT CURRENT
100mA
1D-30
120
QUIESCENT CURRENT (µA)
110
100
90
80
70
60
QUIESCENT CURRENT
5V OUTPUT
QUIESCENT CURRENT (mA)
10
QUIESCENT CURRENT
5V OUTPUT
QUIESCENT CURRENT (mA)
8
7
6
5
4
3
2
1
0
0
QUIESCENT CURRENT
5V OUTPUT
9
V
IN
= 6V
I
L
= 100mA
8
V
IN
= 6V
I
L
= 100µA
I
L
= 100mA
50
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (˚C)
1D-31
7
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (˚C)
1D-32
1
2
3
4
5
6
INPUT VOLTAGE (V)
7
8
1D-33
CALOGIC CORPORATION,
237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025
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