ADMOS LP2950CP-3 100ma low dropout voltage regulator Datasheet

Advanced
Monolithic
Systems
LP2950/LP2951
100mA LOW DROPOUT VOLTAGE REGULATOR
RoHS compliant
FEATURES
APPLICATIONS
• 5V, 3.3V, and 3V Versions at 100mA Output Current
• High Accuracy Output Voltage
• Extremely Low Quiescent Current
• Low Dropout Voltage
• Extremely Tight Load and Line Regulation
• Very Low Temperature Coefficient
• Current and Thermal Limiting
• Needs Minimum Capacitance (1µF) for Stability
• Unregulated DC Positive Transients 60V
• Battery Powered Systems
• Portable Consumer Equipment
• Cordless Telephones
• Portable (Notebook) Computers
• Portable Instrumentation
• Radio Control Systems
• Automotive Electronics
• Avionics
• Low-Power Voltage Reference
ADDITIONAL FEATURES (LP2951 ONLY)
• 1.24V to 29V Programmable Output
• Error Flag Warning of Voltage Output Dropout
• Logic Controlled Electronic Shutdown
GENERAL DESCRIPTION
The LP2950 and LP2951 are micropower voltage regulators ideally suited for use in battery-powered systems. These devices
feature very low quiescent current (typ.75µA), and very low dropout voltage (typ.45mV at light loads and 380mV at 100mA)
thus prolonging battery life. The quiescent current increases only slightly in dropout. The LP2950/LP2951 has positive
transient protection up to 60V and can survive unregulated input transient up to 20V below ground.
The LP2950 and LP2951 were designed to include a tight initial tolerance (typ. 0.5%), excellent load and line regulation (typ.
0.05%), and a very low output voltage temperature coefficient, making these devices useful as a low-power voltage reference.
The LP2950 is offered in the 3-pin TO-92 package. LP2951 is available in 8-pin plastic SOIC and DIP packages and offers
three major additional system features. An error flag output warns of a low output voltage, often due to failing batteries on
input. The LP2951 also features the logic-compatible shutdown input which enables the regulator to be switched on and off.
The LP2951 device may be pin-strapped for a 5V, 3.3V, or 3V output, or programmed from 1.24V to 29V with an external
pair of resistors.
ORDERING INFORMATION
PIN CONNECTION
PACKAGE TYPE
TO-92
8 LEAD PDIP 8 LEAD SOIC
LP2950ACN-X LP2951ACP-X LP2951ACS-X
LP2950CN-X
LP2951CP-X
LP2951CS-X
OPERATING
TEMP. RANGE
IND.
IND
8L SOIC/ 8L PDIP
OUTPUT 1
8 INPUT
SENSE 2
7 FEEDBACK
SHUTDOWN 3
6 VTAP
GROUND 4
X = 3.3V, or 3V
5 ERROR
Top View
TO-92
OUTPUT
INPUT
GND
Bottom View
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LP2950/LP2951
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Supply Voltage
-0.3 to +30V
OPERATING RATINGS
(Note 1)
SHUTDOWN Input Voltage,
Error Comparator Output
Voltage,(Note 9)
FEEDBACK Input Voltage
(Note 9) (Note 10)
Power Dissipation
Junction Temperature
Storage Temperature
Soldering Temperature (25 sec)
Max. Input Supply Voltage
Junction Temperature Range
(TJ) (Note 8)
LP2950AC-XX, LP2950C-XX
LP2951AC-XX, LP2951C-XX
-1.5 to +30V
Internally Limited
+150°C
-65°C to +150°C
260°C
30V
-40°C to +125°C
ELECTRICAL CHARACTERISTICS at Vs=Vout+1V, Ta=25°C, unless otherwise noted.
Parameter
LP2950AC
LP2951AC
Conditions
(Note 2)
Min.
Typ.
LP2950C
LP2951C
Max.
Min.
Typ.
Units
Max.
3 V Versions (Note 16)
Output Voltage
Output Voltage
TJ = 25°C
(Note 3)
-25°C ≤TJ ≤85°C
Full Operating Temperature
Range
100 µA ≤IL ≤100 mA
TJ ≤TJMAX
2.985
3.0
3.015
2.970
3.0
3.030
V
2.970
3.0
3.030
2.955
3.0
3.045
V
2.964
3.0
3.036
2.940
3.0
3.060
V
2.958
3.0
3.042
2.928
3.0
3.072
V
3.284
3.3
3.317
3.267
3.3
3.333
V
3.267
3.3
3.333
3.251
3.3
3.350
V
3.260
3.3
3.340
3.234
3.3
3.366
V
3.254
3.3
3.346
3.221
3.3
3.379
V
4.975
5.0
5.025
4.95
5.0
5.05
V
4.95
5.0
5.050
4.925
5.0
5.075
V
4.94
5.0
5.06
4.90
5.0
5.10
V
4.925
5.0
5.075
4.88
5.0
5.12
V
3.3 V Versions (Note 16)
Output Voltage
Output Voltage
TJ = 25°C
(Note 3)
-25°C ≤TJ ≤85°C
Full Operating Temperature
Range
100 µA ≤IL ≤100 mA
TJ ≤TJMAX
5 V Versions (Note 16)
Output Voltage
Output Voltage
TJ = 25°C
(Note 3)
-25°C ≤TJ ≤85°C
Full Operating Temperature
Range
100 µA ≤IL ≤100 mA
TJ ≤TJMAX
All Voltage Options
Output Voltage
Temperature Coefficient
20
ppm/°C
50
Line Regulation (Note 14)
(Note 12) (Note 4)
6V ≤Vin ≤30V (Note 15)
0.03
0.1
0.04
0.2
%
Load Regulation (Note 14)
100 µA ≤IL ≤ 100 mA
0.04
0.1
0.1
0.2
%
Dropout Voltage
(Note 5)
IL = 100µ A
IL = 100 mA
50
80
50
80
mV
380
450
380
450
mV
Ground Current
IL = 100 µA
IL = 100 mA
75
120
75
120
µA
8
12
8
12
mA
Current Limit
Vout = 0
160
200
160
200
mA
Thermal Regulation
(Note 13)
0.05
0.2
0.05
0.2
%/W
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LP2950/LP2951
ELECTRICAL CHARACTERISTICS (Note 2) (Continued)
PARAMETER
LP2950AC
LP2951AC
CONDITIONS
(Note 2)
Output Noise,
10Hz to 100KHz
Min.
Typ.
CL = 1µF
Reference Voltage
Over Temperature (Note 7)
Reference Voltage Temperature
Coefficient
160
µV rms
100
100
µV rms
LP2951AC
LP2951C
1.235
1.21
1.27
1.185
1.235
1.26
V
V
60
nA
20
50
ppm/°C
0.1
0.1
nA/°C
60
40
( Note 12 )
V
OH
= 30V
0.01
1
0.01
1
µA
150
250
150
250
mV
Output Low Voltage
Vin = 4.5V
IOL = 400µA
Upper Threshold Voltage
(Note 6)
Lower Threshold Voltage
(Note 6)
75
Hysteresis
Shutdown Input
(Note 6)
15
Input logic Voltage
1.25
1.285
40
Feedback Pin Bias Current
Temperature Coefficient
Error Comparator
Output Leakage Current
Units
160
1.19
Feedback Pin Bias Current
Max.
µV rms
(Bypass = 0.01 µF pins 7 to
1(LP2951))
1.22
Typ.
430
CL = 13.3 µF
Reference Voltage
Min.
Max.
430
CL = 200 µF
8-Pin Versions only
LP2950C
LP2951C
40
Low (Regulator ON)
High (Regulator OFF)
60
1.3
40
95
60
75
mV
95
15
0.7
2
mV
mV
1.3
0.7
2
V
V
Shutdown Pin Input Current
(Note 3)
Vs = 2.4V
Vs = 30V
30
50
30
50
µA
450
600
450
600
µA
Regulator Output Current in
Shutdown (Note 3)
(Note 11)
3
10
3
10
µA
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the
device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the
Electrical Characteristics tables.
Note 2: Unless otherwise specified all limits guaranteed for VIN = ( VONOM +1)V, IL = 100 µA and CL = 1 µF for 5V versions and 2.2µF for 3V and 3.3V
versions. Limits appearing in boldface type apply over the entire junction temperature range for operation. Limits appearing in normal type apply for TA = TJ =
25°C Additional conditions for the 8-pin versions are FEEDBACK tied to VTAP, OUTPUT tied to SENSE and VSHUTDOWN ≤ 0.8V.
Note 3: Guaranteed and 100% production tested.
Note 4: Guaranteed but not 100% production tested. These limits are not used to calculate outgoing AQL levels.
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: Comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nominal reference voltage measured at
VIN = ( VONOM +1)V. 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 7: Vref ≤Vout ≤ (Vin - 1V), 2.3 ≤Vin≤30V, 100µA≤IL≤ 100 mA, TJ ≤ TJMAX.
Note 8: The junction-to-ambient thermal resistance are as follows:180°C/W and 160°C/W for the TO-92 (N) package with 0.40 inch and 0.25 inch leads to the
printed circuit board (PCB) respectively, 105°C/W for the molded plastic DIP (P) and 160°C/W for the molded plastic SO-8 (S). The above thermal resistances
for the N, S and P packages apply when the package is soldered directly to the PCB.
Note 9: May exceed input supply voltage.
Note 10: When used in dual-supply systems where the output terminal sees loads returned to a negative supply, the output voltage should be diode-clamped to
ground.
Note 11: Vshutdown ≥ 2V, Vin ≤ 30V, Vout =0, Feedback pin tied to 5VTAP.
Note 12: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range.
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LP2950/LP2951
Note 13: Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load or line
regulation effects. Specifications are for a 50mA load pulse at VIN =30V (1.25W pulse) for T =10 ms.
Note 14: 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 15: Line regulation for the LP2951 is tested at 150°C for IL = 1 mA. 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 16: All LP2950 devices have the nominal output voltage coded as the last two digits of the part number. In the LP2951 products, the 3.0V and 3.3V
versions are designated by the last two digits, but the 5V version is denoted with no code of the part number.
BLOCK DIAGRAM AND TYPICAL APPLICATIONS
LP2950-XX
LP2951-XX
7
FEEDBACK
+
+
INPUT
VOUT
IL≤ 100mA
OUTPUT
ERROR
AMPLIFIER
+
SEE APPLICATION
HINTS
1.23V
REFERENCE
1
OUTPUT
2
FROM
CMOS
OR TTL
-
3
SHUTDOWN
+
50mV
+
8
INPUT
SENSE
+
+
-
VOUT
IL≤ 100mA
UNREGULATED DC
UNREGULATED DC
+
ERROR
AMPLIFIER
6
VTAP
SEE APPLICATION
HINTS
330kΩ
5
+
1.23V
REFERENCE
+
TO CMOS
OR TTL
ERROR
4
GROUND
GROUND
ERROR DETECTION COMPARATOR
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LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Current
Dropout Characteristics
10
Input Current
6
250
225
1
0.1
0.01
0.1
1
10
LOAD CURRENT (mA)
4
RL= 50Ω
2
1
1
125
100
2 3 4 5 6 7 8
INPUT VOLTAGE (V)
75
50
0
9 10
1
QUIESCENT CURRENT ( µA)
5.02
5.0
4.98
0.2%
4.96
IL= 1 mA
100
80
IL= 0
60
40
20
4.94
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
0
0
1
80
70
60
50
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
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2 3
4 5
6
INPUT VOLTAGE (V)
7
8
Quiescent Current
8
5V OUTPUT
5V OUTPUT
9
VIN= 6V
IL= 100mA
8
7
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
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QUIESCENT CURRENT ( µA)
90
QUIESCENT CURRENT (mA)
VIN= 6V
100
9 10
120
Quiescent Current
IL= 100µA
2 3 4 5 6 7 8
INPUT VOLTAGE (V)
5V OUTPUT
140
10
5V OUTPUT
RL= ∞
Quiescent Current
5.04
Quiescent Current
QUIESCENT CURRENT ( µA)
6
5V OUTPUT
RL= 50Ω
0
150
160
5V OUTPUT
120
110
2
3
4
5
INPUT VOLTAGE (V)
RL= 50 kΩ
175
25
0
5.06
OUTPUT VOLTAGE (V)
INPUT CURRENT (mA)
1
0
5V OUTPUT
200
Temperature Drift of 3
Representative Units
Input Current
120
110
100
90
80
70
60
50
40
30
20
10
0
RL= 50 kΩ
3
0
100
INPUT CURRENT ( µA)
OUTPUT VOLTAGE (V)
GROUND CURRENT (mA)
5V OUTPUT
5
7
6
5
IL= 100mA
4
3
2
1
0
0
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1
2 3 4
5
6
INPUT VOLTAGE (V)
Fax (925) 443-0723
7
8
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Short Circuit Current
150
140
130
120
110
500
400
IL= 100mA
300
~
~
100
50
IL= 100µA
0
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
LP2951 Minimum Operating Voltage
1.7
TJ = 25°C
100
0
-10
-20
1mA
10mA
OUTPUT CURRENT
100mA
LP2951 Feedback Pin Current
FEEDBACK CURRENT (µA)
1.8
200
50
10
1.9
300
LP2951 Feedback Bias Current
2.1
2.0
400
0
100µA
20
2.2
BIAS CURRENT (nA)
PIN 7 DRVEN BY EXTERNAL
SOURCE (REGULATOR RUN
OPEN LOOP)
0
-50
TA = 125°C
-100
-150
TA = 25°C
-200
TA = -55°C
-250
-2.0
-30
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
1.6
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
LP2951 Error Comparator Output
LP2951 Comparator Sink Current
9
2.5
7
50k RESISTOR TO
EXTERNAL 5V SUPPLY
6
5
4
HYSTERESIS
3
50k
RESISTOR
TO VOUT
2
1
0
0
1
2 3 4 5 6 7
INPUT VOLTAGE (V)
8
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SINK CURRENT (mA)
VOUT= 5V
8
TA = 125°C
2.0
1.5
TA = 25°C
1.0
TA = -55°C
0.5
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
OUTPUT LOW VOLTAGE (V)
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INPUT OUTPUT VOLTAGE
VOLTAGE
CHANGE
MINIMUM OPERATING VOLTAGE (V)
500
DROPOUT VOLTAGE (mV)
160
DROPOUT VOLTAGE (mV)
SHORT CIRCUIT CURRENT ( mA)
600
100
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
ERROR OUTPUT (V)
Dropout Voltage
Dropout Voltage
170
0
0.5
-1.5 -1.0 -0.5
FEEDBACK VOLTAGE (V)
1.0
Line Transient Response
100
mV
50
mV
0
-50
mV
CL= 1µF
IL= 1mA
~
~
VOUT= 5V
8V
6V
4V
0
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200
400
TIME (µs)
600
Fax (925) 443-0723
800
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
100
mA
100
µA
1
2
3
TIME (ms)
4
5
0
RIPPLE REJECTION (dB)
IO= 100mA
IO= 1 mA
0.5
0.2
VOUT = 5V
CL= 1 µF
0.05
0.02
0.01
16
OUTPUT
VOLTAGE (V)
20
5
4
3
2
1
0
2
80
80
70
IL= 0
50
IL= 100µA
CL= 1 µF
VIN= 6V
30
~
~
Ripple Rejection
90
40
CL= 10 µF
IL= 10 mA
VIN = 8V
VOUT = 5V
0
-2
-100 0 100 200 300 400 500 600 700
TIME (µs)
90
60
CL= 1 µF
VOUT = 5V
70
CL= 1 µF
VIN= 6V
VOUT = 5V
IL= 1mA
60
50
40
30
IL= 10mA
10
100
1K
10K 100K
FREQUENCY (Hz)
20
10 1
1M
Ripple Rejection
60
IL= 100mA
CL= 1µF
VIN= 6V
30
VOUT= 5V
20
10
10 1
10 6
10 2
10 5
10 3
10 4
FREQUENCY (Hz)
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10 6
IL= 100mA
CL= 1 µF
2.5
2.0
1.5
CL= 3.3 µF
CL= 220 µF
1.0
0.0
10 5
10 3
10 4
FREQUENCY (Hz)
10 6
LP2951 Divider Resistance
3.0
0.5
10 2
400
5V OUTPUT
IL= 50mA
50
40
10 5
10 3
10 4
FREQUENCY (Hz)
3.5
VOLTAGE NOISE SPECTRAL
DENSITY(mV/√Hz)
70
10 2
20
10 1
LP2951 Output Noise
80
RIPPLE REJECTION (dB)
8
12
TIME (ms)
PIN 2 TO PIN 4 RESISTANCE (k Ω)
OUPUT IMPEDANCE (Ω)
2
0.1
4
7
6
Ripple Rejection
IO= 100µA
1
VOUT = 5V
~
~
Output Impedance
10
5
CL= 10 µF
RIPPLE REJECTION (dB)
0
100
mA
100
µA
LP2951 Enable Transient
SHUTDOWN PIN
VOLTAGE (V)
CL= 1 µF
VOUT = 5V
~
~
OUTPUT VOLTAGE
CHANGE (mV)
Load Transient Response
80
60
40
20
0
-20
-40
-60
LOAD
CURRENT
LOAD
CURRENT
OUTPUT VOLTAGE
CHANGE (mV)
Load Transient Response
250
200
150
100
50
0
-50
-100
0.01 µF
BYPASS
PIN 1 TO
PIN 7
10 2
10 3
10 4
FREQUENCY (Hz)
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10 5
300
200
100
0
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
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LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
1.6
REGULATOR OFF
1.2
1.0
REGULATOR ON
0.8
0.6
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (° C)
30
25
20
15
10
5
0
120
OUTPUT CURRENT ( mA)
1.8
1.4
LP2951 Maximum Rated
Output Current
Line Regulation
OUTPUT VOLTAGE CHANGE (V)
SHUTDOWN TRESHOLD VOLTAGE (V)
Shutdown Treshold Voltage
IL= 100µA
TJ = 150° C
IL= 1mA
~
~
10
5
0
-5
-10
IL= 100µA
TJ = 125° C
15
20
25
10
INPUT VOLTAGE (V)
TJMAX= 125° C
60
TA= 25° C
40
TA= 85° C
0
0
10
5
15
20
INPUT VOLTAGE (V)
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25
30
POWER
OUTPUT VOLTAGE
DISSIPATION (W) CHANGE (mV)
OUTPUT CURRENT ( mA)
TO-92 PACKAGE
.25"LEADS SOLDERED
TO PC BOARD
20
TJMAX= 125° C
VOUT = 5V
80
TA= 25° C
60
TA= 50° C
40
20
TA= 85° C
30
10
5
15
20
INPUT VOLTAGE (V)
0
Thermal Response
120
80
100
0
5
LP2950 Maximum Rated
Output Current
100
8 PIN MOLDED
DIP SOLDERED
TO PC BOARD
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5
4
2
0
-2
1
~
~
1.25W
0
-1
0
10
20
30
TIME (µs)
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40
50
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25
30
LP2950/LP2951
APPLICATION HINTS
External Capacitors
A 1.0 µF or greater capacitor is required between output and
ground for stability at output voltages of 5V or more. At lower
output voltages, more capacitance is required (2.2µ or more is
recommended for 3V and 3.3V versions). Without this capacitor
the part will oscillate. Most types of tantalum or aluminum
electrolytic works fine here; even film types work but are not
recommended for reasons of cost. Many aluminum types have
electrolytes that freeze at about -30°C, so solid tantalums are
recommended for operation below -25°C. The important
parameters of the capacitor are an ESR of about 5 Ω or less and
resonant frequency above 500 kHz parameters in the value of the
capacitor. The value of this capacitor may be increased without
limit.
At lower values of output current, less output capacitance is
required for stability. The capacitor can be reduced to 0.33 µF for
currents below 10 mA or 0.1 µF for currents below 1 mA. Using
the adjustable versions at voltages below 5V runs the error
amplifier at lower gains so that more output capacitance is needed.
For the worst-case situation of a 100mA load at 1.23V output
(Output shorted to Feedback) a 3.3µF (or greater) capacitor should
be used.
Unlike many other regulators, the LP2950, will remain stable and
in regulation with no load in addition to the internal voltage
divider. This is especially important in CMOS RAM keep-alive
applications. When setting the output voltage of the LP2951
version with external resistors, a minimum load of 1µA is
recommended.
A 1µF tantalum or aluminum electrolytic capacitor should be
placed from the LP2950/LP2951 input to the ground 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.
Stray capacitance to the LP2951 Feedback terminal can cause
instability. This may especially be a problem when using a higher
value of external resistors to set the output voltage. Adding a 100
pF capacitor between Output and Feedback and increasing the
output capacitor to at least 3.3 µF will fix this problem.
Error Detection Comparator Output
The comparator produces a logic low output whenever the LP2951
output falls out of regulation by more than approximately 5%.
This figure is the comparator’s built-in offset of about 60 mV
divided by the 1.235 reference voltage. (Refer to the block
diagram in the front of the datasheet.) This trip level remains “5%
below normal” regardless of the programmed output voltage of the
2951. For example, the error flag trip level is typically 4.75V for a
5V output or 11.4V for a 12V output. The out of regulation
condition may be due either to low input voltage, current limiting,
or thermal limiting.
Figure 1 gives a timing diagram depicting the ERROR signal and
the regulator output voltage as the LP2951 input is ramped up and
down. For 5V versions the ERROR signal becomes valid (low) at
about 1.3V input. It goes high at about 5V input (the input voltage
at which Vout = 4.75 ).
Since the LP2951’s dropout voltage is load dependent (see curve
in typical performance characteristics), the input voltage trip point
(about 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. This resistor may be returned to the
output or some other supply voltage depending on system
requirements. In determining a value for this resistor, note that
the output is rated to sink 400µA, this sink current adds to battery
drain in a low battery condition. Suggested values range from
100K to 1MΩ. The resistor is not required if this output is unused.
Programming the Output Voltage (LP2951)
The LP2951 may be pin-strapped for the nominal fixed output
voltage using its internal voltage divider by tying the output and
sense pins together, and also tying the feedback and VTAP pins
together. Alternatively, 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.
The complete equation for the output voltage is:
Vout = VREF × (1 + R1/ R2)+ IFBR1
where VREF is the nominal 1.235 reference voltage and IFB is the
feedback pin bias current, nominally -20 nA. The minimum
recommended load current of 1 µA forces an upper limit of 1.2
MΩ on value of R2, if the regulator must work with no load (a
condition often found in CMOS in standby) IFB will produce a 2%
typical error in VOUT which may be eliminated at room
temperature by trimming R1. For better accuracy, choosing R2 =
100k reduces this error to 0.17% while increasing the resistor
program current by 12 µA. Since the LP2951 typically draws 60
µA at no load with Pin 2 open-circuited, this is a small price to
pay.
Reducing Output Noise
In reference applications it may be an advantageous to reduce the
AC noise present at the output. One method 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 1 µF to 220 µF only decreases the noise from 430 µV to 160
µV rms for a 100 kHz 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 about 0.01 µF. When doing this, the output capacitor must be
increased to 3.3 µF to maintain stability. These changes reduce
the output noise from 430 µV to 100 µV rms for a 100 kHz
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.
LP2950/LP2951
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
APPLICATION HINTS (Continued)
+VIN
OUTPUT
VOLTAGE
4.75V
8
100k
VOUT
1.2
30V
+VIN
ERROR
OUPUT
ERROR*
**SHUTDOWN
INPUT
5V
INPUT
VOLTAGE
5 ERROR*
3
VOUT
LP2951
SD
R1
GND
4
1.3V
1
FB
7
3.3µF
1.23V
VREF
FIGURE 1. ERROR Output Timing
* +
.01
µF
R2
FIGURE 2. Adjustable Regulator
*When VIN ≤1.3V the error flag pin becomes a high impedance,
and the error flag voltage rises to its pull-up voltage. Using Vout
as the pull-up voltage (see Figure 2), rather than an external 5V
source, will keep the error flag voltage under 1.2V (typ.) in this
condition. The user may wish to drive down the error flag
voltage using equal value resistors (10 kΩ suggested), to ensure a
low-level logic signal during any fault condition, while still
allowing a valid high logic level during normal operation.
*See Application Hints.
Vout = VREF × (1 + R1/ R2)
**Drive with TTL- high to shut down. Ground or leave if shutdown
feature is not used.
Note: Pins 2 and 6 are left open.
TYPICAL APPLICATIONS
300 mA Regulator with 0.75 Dropout
Wide Input Voltage Range Current Limiter
UNREGULATED
INPUT
+VIN
8
IN
OUT
1
VTAP
FB
7
SENSE
GND
4
2N5432 (2)
8
27kΩ
LP2951
6
330Ω
+VIN
ERROR
OUPUT
5V OUTPUT
2
4.7µF
5
ERROR
VOUT
1
*VOUT ≈ VΙΝ
LP2951
LOAD
50mA TO
300mA
SHUTDOWN 3
SD
INPUT
GND
4
FB
7
*Minimum Input-Output voltage ranges from 40mV to 400mV, depending on
load current. Current limit is typically 160 mA
LP2950/LP2951
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
TYPICAL APPLICATIONS (Continued)
Low Drift Current Source
30V
+V = 2
IL
5Volt Current Limiter
LOAD
5V BUS
8
+VIN
VIN
VOUT
1
*VOUT ≈ 5V
LP2950 -5.0
VOUT
LP2951
SHUTDOWN 3
SD
INPUT
0.1µF
GND
FB
4
7
R
1%
1µF
GND
1µF
+
*Minimum Input-Output voltage ranges from 40mV to 400mV, depending on
load current. Current limit is typically 160 mA
5V Regulator with 2.5V Sleep Function
Open Circuit Detector for 4 to 20mA Current Loop
+VIN
+5V
C - MOS
GATE
*SLEEP
INPUT
4.7kΩ
4
20mA
*OUTPUT
1
8
47kΩ
470kΩ
+VIN
8
VOUT
+VIN
ERROR
OUPUT
5
ERROR
+VOUT
VOUT 1
GND
FB
4
7
4
7
1%
+
3.3µF
2N3906
100kΩ
1%
100kΩ
Advanced Monolithic Systems, Inc.
2
FB
200kΩ
100pF
1
LP2951
1N4001
LP2951
SHUTDOWN 3
SD
INPUT
5
www.advanced-monolithic.com
0.1µF
GND
4
1N457
360
MIN. VOLTAGE ≈ 4V
Phone (925) 443-0722
Fax (925) 443-0723
LP2950/LP2951
TYPICAL APPLICATIONS (Continued)
2 Ampere Low Dropout Regulator
CURRENT
LIMIT SECTION
Regulator with Early Warning and Auxiliary Output
+VIN
+VIN = VOUT +.5V
0.05
680
D1
8
+VIN
6
470
7
4.7MΩ
VOUT
7
FB
GND
VOUT
4
1
ERROR
FLAG
5
LP2951
220
1µF
3.6V
NICAD
4
27 kΩ
ERROR
SD
20
+
GND
+VIN
3
5V MEMORY
SUPPLY
D2
1
LP2951
#1
5
ERROR
FB
+VOUT @ 2A
10kΩ
8
SENSE
VTAP
MJE2955
2N3906
2
+
R1
+
4.7
TANT.
100µF
EARLY WARNING
D3
2.7MΩ
D4
1%
R2
Q1
20kΩ
8
+VIN
6
.033
2
SENSE
VTAP
7
FB
3
SD
RESET
330 kΩ
MAIN 5V OUTPUT
VOUT
LP2951
#2
5
ERROR
+
µP
VDD
1µF
GND
4
VOUT = 1.23V(1+R1/R2)
For 5V VOUT, use internal resistors. Wire pin 6 to 7 and pin 2 to +VOUTBuss.
•
Early warning flag on low input voltage
•
Main output latches off at lower input voltages
•
Battery backup on auxiliary output
Operation: Reg.#1’s VOUT is programmed one diode drop above 5V. It’s error flag
becomes active when VIN≤ 5.7V. When VIN drops below 5.3V, the error flag of
Reg.#2 becomes active and via Q1 latches the main output off. When VIN again
exceeds 5.7V Reg.#1 is back in regulation and the early warning signal rises,
unlatching Reg.#2 via D3.
1A Regulator with 1.2V Dropout
Latch Off When Error Flag Occurs
+VIN
UNREGULATED
INPUT
0.01µF
10kΩ
1µF
SUPERTEX
VP12C
470kΩ
8
IN
6
VTAP
SENSE
1ΜΩ
OUTPUT
5V ± 1% @
0 TO 1A
2
+
LP2951
7
GND
4
470kΩ
LP2951
3 SD
0.002µF
RESET
VOUT
+VIN
1
VOUT
ERROR
R1
220µF
OUT 1
FB
8
5
FB
GND
4
7
+
1µF
R2
2kΩ
IQ ≅ 400µA
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
LP2950/LP2951
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
3 LEAD TO-92 PLASTIC PACKAGE (N)
0.180±0.005
(4.572±0.127)
0.060±0.005
(1.524±0.127)
DIA
0.060±0.010
(1.524±0.254)
0.90
(2.286)
NOM
0.180±0.005
(4.572±0.127)
0.140±0.010
(3.556±0.127)
5° NOM
0.500
(12.70)
MIN
0.050
(1.270)
MAX
UNCONTROLLED
LEAD DIMENSIONS
0.015±0.002
(0.381±0.051)
0.016±0.003
(0.406±0.076)
0.050±0.005
(1.270±0.127)
10°
NOM
N (TO-92 ) AMS DRW# 042391
8 LEAD SOIC PLASTIC PACKAGE (S)
0.189-0.197*
(4.801-5.004)
8
7
6
5
0.228-0.244
(5.791-6.197)
0.150-0.157**
(3.810-3.988)
1
2
3
4
0.010-0.020 x 45°
(0.254-0.508)
0.053-0.069
(1.346-1.752)
0.004-0.010
(0.101-0.254)
0.014-0.019
(0.355-0.483)
0.008-0.010
(0.203-0.254)
0.050
(1.270)
TYP
0°-8° TYP
0.016-0.050
(0.406-1.270)
S (SO-8 ) AMS DRW# 042293
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
LP2950/LP2951
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued).
8 LEAD PLASTIC DIP PACKAGE (P)
0.400*
(10.160)
MAX
8
7
6
5
1
2
3
4
0.255±0.015*
(6.477±0.381)
0.045-0.065
(1.143-1.651)
0.300-0.325
(7.620-8.255)
0.130±0.005
(3.302±0.127)
0.065
(1.651)
TYP
0.005
(0.127)
MIN
0.100±0.010
(2.540±0.254)
0.125
(3.175)
MIN
0.009-0.015
(0.229-0.381)
0.015
(0.380)
MIN
0.018±0.003
(0.457±0.076)
0.325 +0.025
-0.015
(8.255 +0.635 )
-0.381
P (8L PDIP ) AMS DRW# 042294
*DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS.
MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.010" (0.254mm)
Advanced Monolithic Systems, Inc.
www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723