Advanced Monolithic Systems LP2950CS-3.3, LP2950CS-3.0, LP2950CP-3.3, LP2950CN-3.3, LP2950CN-3.0 Datasheet

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Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
Advanced LP2950/LP2951 Monolithic 100mA LOW DROPOUT VOLTAGE REGULATOR Systems
FEATURES APPLICATIONS
•• 5V, 3.3V, and 3V Versions at 100mA Output Current •• Battery Powered Systems
•• High Accuracy Output Voltage •• Portable Consumer Equipment
•• Extremely Low Quiescent Current •• Cordless Telephones
•• Extremely Tight Load and Line Regulation •• Portable Instrumentation
•• Very Low Temperature Coefficient •• Radio Control Systems
•• Current and Thermal Limiting •• Automotive Electronics
•• Needs Minimum Capacitance (1µµF) for Stability •• Avionics
•• Unregulated DC Positive Transients 60V •• 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
OPERATING
TO-92
8 LEAD PDIP
8 LEAD SOIC
TEMP. RANGE
LP2950ACN-X
LP2951ACP-X
LP2951ACS-X
IND.
LP2950CN-X
LP2951CP-X
LP2951CS-X
IND
X = 3.3V, or 3V
8L SOIC/ 8L PDIP
1 2
8
4
3
7
5
6 V
TAP
ERROR
FEEDBACK
OUTPUT
SENSE
SHUTDOWN
INPUT
GROUND
Top View
TO-92
OUTPUT
INPUT
GND
Bottom View
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Supply Voltage -0.3 to +30V Wave
4 seconds, 260°C
SHUTDOWN Input Voltage, Infrared
4 seconds, 240°C
Error Comparator Output Vapor Phase
4 seconds, 219°C
Voltage,(Note 9) ESD TBD FEEDBACK Input Voltage -1.5 to +30V (Note 9) (Note 10)
OPERATING RATINGS (Note 1)
Power Dissipation Internally Limited Junction Temperature
+150°C
Max. Input Supply Voltage 30V
Storage Temperature
-65°C to +150°C
Junction Temperature Range
Soldering Dwell Time, Temperature (TJ) (Note 8)
LP2950AC-XX, LP2950C-XX LP2951AC-XX, LP2951C-XX
-40°C to +125°C
ELECTRICAL CHARACTERISTICS at V
s
=Vout+1V, Ta=25°C, unless otherwise noted.
Parameter Conditions
(Note 2)
LP2950AC LP2951AC
Min. Typ. Max.
LP2950C LP2951C
Min. Typ. Max.
Units
3 V Versions (Note 16)
Output Voltage
TJ = 25°C (Note 3)
-25°C TJ ≤85°C Full Operating Temperature Range
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
Output Voltage
100 µA ≤IL 100 mA TJ ≤T
JMAX
2.958
3.0
3.042 2.928
3.0
3.072
V
3.3 V Versions (Note 16) Output Voltage
TJ = 25°C (Note 3)
-25°C TJ ≤85°C Full Operating Temperature Range
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
Output Voltage
100 µA ≤IL 100 mA TJ ≤T
JMAX
3.254
3.3
3.346 3.221
3.3
3.379
V
5 V Versions (Note 16) Output Voltage
TJ = 25°C (Note 3)
-25°C TJ ≤85°C Full Operating Temperature Range
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
Output Voltage
100 µA ≤IL 100 mA TJ ≤T
JMAX
4.925
5.0
5.075 4.88
5.0
5.12
V
All Voltage Options
Output Voltage Temperature Coefficient (Note 12) (Note 4)
20 50
ppm/°C
Line Regulation (Note 14)
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
380
80
450
50
380
80
450
mV mV
Ground Current
IL = 100 µA IL = 100 mA
75
8
120
12
75
8
120
12
µA
mA
Current Limit
V
out
= 0 160 200 160 200 mA
Thermal Regulation (Note 13) 0.05 0.2 0.05 0.2 %/W
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
ELECTRICAL CHARACTERISTICS (Note 2) (Continued)
PARAMETER CONDITIONS
(Note 2)
LP2950AC LP2951AC
Min. Typ. Max.
LP2950C LP2951C
Min. Typ. Max.
Units
Output Noise, 10Hz to 100KHz
CL = 1µF CL = 200 µF CL = 13.3 µF (Bypass = 0.01 µF pins 7 to
1(LP2951))
430 160 100
430 160 100
µV rms µV rms µV rms
8-Pin Versions only LP2951AC LP2951C
Reference Voltage 1.22 1.235 1.25 1.21 1.235 1.26 V Reference Voltage Over Temperature (Note 7)
1.19 1.27 1.185 1.285
V
Feedback Pin Bias Current 40 60 40 60 nA
Reference Voltage Temperature Coefficient
( Note 12 )
20 50 ppm/°C
Feedback Pin Bias Current Temperature Coefficient
0.1 0.1 nA/°C
Error Comparator
Output Leakage Current
V
OH
= 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 6) 40 60 40 60 mV
Lower Threshold Voltage
(Note 6) 75 95 75 95 mV
Hysteresis
(Note 6) 15 15 mV
Shutdown Input
Input logic Voltage
Low (Regulator ON) High (Regulator OFF)
2
1.3
0.7 2
1.3
0.7
V V
Shutdown Pin Input Current (Note 3)
Vs = 2.4V Vs = 30V
30 450
50 600
30 450
50 600
µA 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 V
IN
= ( V
ONOM
+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 V
TAP
, OUTPUT tied to SENSE and V
SHUTDOWN
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 V
IN
= ( V
ONOM
+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 V
out
as V
out
is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
Note 7: V
ref ≤Vout
(Vin - 1V), 2.3 ≤Vin≤30V, 100µA≤IL≤ 100 mA, TJ ≤ T
JMAX
.
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: V
shutdown
2V, Vin 30V, V
out
=0, Feedback pin tied to 5V
TAP
.
Note 12: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range.
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
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
INPUT
OUTPUT
GROUND
ERROR AMPLIFIER
1.23V REFERENCE
UNREGULATED DC
V
OUT
IL≤ 100mA
SEE APPLICATION
HINTS
+
+
+
+
-
INPUT OUTPUT
GROUND
ERROR AMPLIFIER
1.23V REFERENCE
UNREGULATED DC
V
OUT
I
L
100mA
SEE APPLICATION
HINTS
+
+
+
+
-
FEED­BACK
SHUT-
DOWN
SENSE
V
TAP
ERROR
TO CMOS OR TTL
+
-
+
330k
4
5
6
2
187
3
FROM CMOS
OR TTL
50mV
ERROR DETECTION COMPARATOR
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS
0
40
100
60
160
0 1 2 3 4 5 6 7 8
INPUT VOLTAGE (V)
Quiescent Current
QUIESCENT CURRENT (µA)
125
250
Input Current
25
50
75
100
150
175
200
225
INPUT VOLTAGE (V)
INPUT CURRENT (µA)
5V OUTPUT
-75 0 25 50 75 100 125
5.06
5.0
150
OUTPUT VOLTAGE (V)
Temperature Drift of 3 Representative Units
TEMPERATURE (° C)
5.04
4.98
4.94
-50 -25
0.1 1 10 100 LOAD CURRENT (mA)
GROUND CURRENT (mA)
0.01
0.1
1
10
Quiescent Current
Dropout Characteristics
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
RL= 50 k
0
60
120
Input Current
10
20
30
50
70
80
90
100
INPUT VOLTAGE (V)
INPUT CURRENT (mA)
-75
0 25 50 75 100 125
120
90
150
QUIESCENT CURRENT (
µ
A)
Quiescent Current
TEMPERATURE (° C)
100
70
60
-50 -25
IL= 100µA
-75
0 25 50 75 100 12510150
QUIESCENT CURRENT (mA)
Quiescent Current
TEMPERATURE (° C)
9
8
7
-50 -25
IL= 100mA
50
80
110
20
80
140 120
0
2
5
3
8
0 1 2 3 4 5 6 7 8
INPUT VOLTAGE (V)
Quiescent Current
QUIESCENT CURRENT (µA)
1
4
7 6
0
1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 100
0
1
2
3
4
5
6
0
1 2 3 4 5 6 7 8 9 100
40
110
5.02
4.96
5V OUTPUT
5V OUTPUT5V OUTPUT 5V OUTPUT
5V OUTPUT
5V OUTPUT
5V OUTPUT
IL= 1 mA
IL= 100mA
RL= 50
RL= 50 k
IL= 0
VIN= 6V
VIN= 6V
RL= 50
0.2%
RL=
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
-75 0 25 50 75 100 125
170
140
150
SHORT CIRCUIT CURRENT (mA)
Short Circuit Current
TEMPERATURE (° C)
150
120
110
-50 -25 -75 0 25 50 75 100 125
600
150
DROPOUT VOLTAGE (mV)
Dropout Voltage
TEMPERATURE (° C)
400
100
0
-50 -25
IL= 100mA
100
130
160
-75 0
25 50 75
100
125
2.2
150
MINIMUM OPERATING VOLTAGE (V)
LP2951 Minimum Operating Voltage
TEMPERATURE (° C)
-50 -25
-75 0 25 50 75 100
125
20
150
BIAS CURRENT (nA)
LP2951 Feedback Bias Current
TEMPERATURE (° C)
0
-30
-50 -25 -2.0 -1.5 -1.0 -0.5
0 0.5
-250
50
-50
-150
LP2951 Feedback Pin Current
1.0
FEEDBACK VOLTAGE (V)
FEEDBACK CURRENT (µA)
-200
0
-100
200 400 600
100 mV
800
INPUT
VOLTAGE
Line Transient Response
TIME (µs)
0
8V
4V
0
IL= 1mA
V
OUT
= 5V
0.0 0.3 0.4 0.5 0.6 0.7 0.8
2.5
0.9
SINK CURRENT (mA)
LP2951 Comparator Sink Current
OUTPUT LOW VOLTAGE (V)
1.5
0.0
0.1 0.20 3 4 5 6 7 8
9
4
ERROR OUTPUT (V)
LP2951 Error Comparator Output
INPUT VOLTAGE (V)
5
2 1
1 2
0
3
6
V
OUT
= 5V
100µA 1mA 10mA 100mA
OUTPUT CURRENT
DROPOUT VOLTAGE (mV)
0
500
Dropout Voltage
500
300
50
400
300
200
100
2.1
2.0
1.9
1.8
1.7
1.6
10
-10
-20
50
mV
-50
mV
6V
OUTPUT VOLTAGE
CHANGE
~
~
~
~
8 7
2.0
1.0
0.5
IL= 100µA
TJ = 25°C
TA = 125°C
TA = 25°C
TA = -55°C
PIN 7 DRVEN BY EXTERNAL SOURCE (REGULATOR RUN
OPEN LOOP)
TA = 125°C
TA = 25°C
TA = -55°C
CL= 1µF
HYSTERESIS
50k RESISTOR TO EXTERNAL 5V SUPPLY
50k RESISTOR TO V
OUT
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Load Transient Response
TIME (ms)
OUTPUT VOLTAGE
CHANGE (mV)
CL= 1 µF
0 1 2 3 4 5
100
0
50
150
250
V
OUT
= 5V
2
7
LP2951 Enable Transient
0
2
0
1
3
4
5
6
TIME (µs)
SHUTDOWN PIN
VOLTAGE (V)
0 100 200 300 400 500 600 700-100
-2
IL= 10 mA
200
100
-50
-100
100
mA
µ
A
~
~
~
~
LOAD
CURRENT
Load Transient Response
TIME (ms)
OUTPUT VOLTAGE
CHANGE (mV)
0 4 8 12 16 20
100
-20
0
40
80 60
20
-40
-60
100
mA
µ
A
~
~
LOAD
CURRENT
OUTPUT
VOLTAGE (V)
CL= 10 µF
V
OUT
= 5V
V
OUT
= 5V
CL= 10 µF
CL= 1 µF
V
IN
= 8V
10 100 1K 100K
FREQUENCY (Hz)
OUPUT IMPEDANCE (
)
0.01
10
Output Impedance
2 1
0.05
0.02
10
1
10
4
10
5
90
60
10
6
RIPPLE REJECTION (dB)
Ripple Rejection
FREQUENCY (Hz)
70
40
30
10
2
IL= 100µA
20
50
80
VIN= 6V
10
3
10
1
10
4
10
5
90
60
10
6
RIPPLE REJECTION (dB)
Ripple Rejection
FREQUENCY (Hz)
70
40
30
10
2
IL= 1mA
20
50
80
VIN= 6V
10
3
10
1
10
4
10
5
80
50
10
6
RIPPLE REJECTION (dB)
Ripple Rejection
FREQUENCY (Hz)
60
30
20
10
2
IL= 50mA
10
40
70
VIN= 6V
10
3
FREQUENCY (Hz)
VOLTAGE NOISE SPECTRAL
DENSITY(mV/
Hz)
0.0
3.5
LP2951 Output Noise
2.0
1.5
0.5
10
4
10
5
10
2
10
3
1.0
3.0
2.5
-75 0 25 50 75 100 125
400
200
150
PIN 2 TO PIN 4 RESISTANCE (k
)
LP2951 Divider Resistance
TEMPERATURE (° C)
300
100
-50 -25
0
5
0.1
0.2
0.5
10K 1M
CL= 1 µF
IL= 100mA
CL= 220 µF
CL= 3.3 µF
0.01 µF BYPASS PIN 1 TO PIN 7
5V OUTPUT
IL= 100mA
CL= 1µF
V
OUT
= 5V
CL= 1 µF
V
OUT
= 5V
IO= 1 mA
IO= 100µA
IO= 100mA
V
OUT
= 5V
CL= 1 µF
IL= 0
V
OUT
= 5V
CL= 1 µF
IL= 10mA
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
-75 0 25 50 75 100 125
1.8
1.2
150
SHUTDOWN TRESHOLD VOLTAGE (V)
Shutdown Treshold Voltage
TEMPERATURE (° C)
1.6
1.0
0.6
-50 -25
1.4
0.8
REGULATOR OFF
0 5
10
15 20 25
0
120
80
40
LP2951 Maximum Rated Output Current
30
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
20
100
60
0
5
Thermal Response
0
1
-2
2
4
TIME (µs)
POWER
DISSIPATION (W)
10 20 30 40 500
-1
5 15 20 25
30
0
30
OUTPUT VOLTAGE CHANGE (V)
Line Regulation
INPUT VOLTAGE (V)
10
-10 10
IL= 100µA
10
-5
5 0
~
~
5
25 20
15
0 5
10
15 20 25
0
120
80
40
LP2950 Maximum Rated Output Current
30
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
20
100
60
~
~
OUTPUT VOLTAGE
CHANGE (mV)
1.25W
TA= 25° C
TA= 50° C
TA= 25° C
TA= 85° C
TA= 85° C
T
JMAX
= 125° C
V
OUT
= 5V
8 PIN MOLDED DIP SOLDERED TO PC BOARD
REGULATOR ON
TO-92 PACKAGE .25"LEADS SOLDERED TO PC BOARD
T
JMAX
= 125° C
IL= 1mA
IL= 100µA
TJ = 150° C
TJ = 125° C
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
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 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 1M. 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 V
TAP
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:
V
out
= V
REF
× (1 + R1/ R2)+ IFBR
1
where V
REF
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 M 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 V
OUT
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
C
BYPASS
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.
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
APPLICATION HINTS (Continued)
OUTPUT
VOLTAGE
ERROR*
INPUT
VOLTAGE
4.75V
5V
1.3V
R
1
ERROR*
ERROR
OUPUT
**SHUTDOWN INPUT
GND FB
V
OUT
V
REF
R
2
SD
1.23V
74
3
8
15
+V
IN
+V
IN
V
OUT
1.2 30V
3.3µF
.01
µF
+*
100k
LP2951
FIGURE 1. ERROR Output Timing FIGURE 2. Adjustable Regulator
*When V
IN
1.3V the error flag pin becomes a high impedance,
and the error flag voltage rises to its pull-up voltage. Using V
out
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 k 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. V
out
= V
REF
× (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
LOAD 50mA TO 300mA
GNDFB
OUTIN
47
6
2
18
V
TAP
LP2951
2N5432 (2)
SENSE
5V OUTPUT
4.7µF
27kΩ
330Ω
ERROR
ERROR OUPUT
SHUTDOWN INPUT
GND FB
V
OUT
SD
74
3
8
15
+V
IN
+V
IN
LP2951
*V
OUT
V
ΙΝ
*Minimum Input-Output voltage ranges from 40mV to 400mV, depending on load current. Current limit is typically 160 mA
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
TYPICAL APPLICATIONS (Continued)
Low Drift Current Source 5Volt Current Limiter
SHUTDOWN INPUT
GND FB
V
OUT
SD
74
3
8
1
V
IN
+V = 2
LP2951
LOAD
30V
I
L
R
1%
1µF
0.1µF
+
GND
V
OUT
+V
IN
5V BUS
LP2950 -5.0
*V
OUT
5V
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
ERROR
ERROR OUPUT
SHUTDOWN INPUT
GND FB
V
OUT
SD
74
3
8
15
+V
IN
+V
IN
LP2951
C - MOS GATE
200k
100k
100k
3.3µF
470k
47k
*SLEEP
INPUT
1%
1%
100pF
2N3906
+V
OUT
+
GND
V
OUT
+V
IN
+5V
LP2951
*OUTPUT
0.1µF
FB
4.7k
360
1N4001
1N457
4
8
1
4
MIN. VOLTAGE4V
20mA
7
2
1
5
4
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
TYPICAL APPLICATIONS (Continued)
2 Ampere Low Dropout Regulator Regulator with Early Warning and Auxiliary Output
ERROR
ERROR FLAG
CURRENT LIMIT SECTION
GND
FB
V
OUT
SD
14
3
8
5
7
+V
IN
+V
IN
= V
OUT
+.5V
LP2951
+V
OUT
@ 2A
R
1
R
2
10k
100µF
4.7
TANT.
++
1%
220
.033
20k
4.7M
2N3906
0.05
680
470
MJE2955
ERROR
GND
FB
V
OUT
5
4
8
1
6
+V
IN
LP2951
#1
V
TAP
7
ERROR
GND
FB
V
OUT
4
8
6
+V
IN
LP2951
#2
V
TAP
3
SD
7
SENSE
2
5
RESET
1µF
20
+V
IN
D
1
D
2
3.6V NICAD
27 k
2.7M
330 k
1µF
D
4
Q
1
MAIN 5V OUTPUT
µP
V
DD
2
D
3
5V MEMORY SUPPLY
EARLY WARNING
SENSE
+
+
VOUT = 1.23V(1+R1/R2)
For 5V V
OUT
, use internal resistors. Wire pin 6 to 7 and pin 2 to +V
OUT
Buss.
Early warning flag on low input voltage
Main output latches off at lower input voltages
Battery backup on auxiliary output
Operation: Reg.#1’s V
OUT
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
OUTPUT 5V ± 1% @ 0 TO 1A
GND
FB OUT
IN
4
7
6
1
2
8
V
TAP
LP2951
SUPERTEX VP12C
SENSE
0.002µ
F
2kΩ
10kΩ
1ΜΩ
0.01µ
F
220µ
F
F
+
IQ ≅
400µA
UNREGULATED
INPUT
R
1
ERROR
GND
FB
V
OUT
R
2
SD
7
4
3
8
15
+V
IN
+V
IN
V
OUT
1µF
+
470k
LP2951
470k
RESET
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
3 LEAD TO-92 PLASTIC PACKAGE (N)
8 LEAD SOIC PLASTIC PACKAGE (S)
0.140±0.010
(3.556±0.127)
0.060±0.010
(1.524±0.254)
0.015±0.002
(0.381±0.051)
0.016±0.003
(0.406±0.076)
0.050±0.005
(1.270±0.127)
0.060±0.005
(1.524±0.127)
DIA
0.180±0.005
(4.572±0.127)
0.180±0.005
(4.572±0.127)
0.050
(1.270)
MAX
0.500
(12.70)
MIN
UNCONTROLLED LEAD DIMENSIONS
10°
NOM
5° NOM
N (TO-92 ) AMS DRW# 042391
0.90
(2.286)
NOM
0°-8° TYP
0.010-0.020 (0.254-0.508)
S (SO-8 ) AMS DRW# 042293
x 45°
0.016-0.050
(0.406-1.270)
0.008-0.010
(0.203-0.254)
0.004-0.010
(0.101-0.254)
0.014-0.019
(0.355-0.483)
0.053-0.069
(1.346-1.752)
0.050
(1.270)
TYP
0.150-0.157**
(3.810-3.988)
0.228-0.244
(5.791-6.197)
0.189-0.197*
(4.801-5.004)
*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
1 2 3 4
8 7 6 5
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued).
8 LEAD PLASTIC DIP PACKAGE (P)
0.045-0.065
(1.143-1.651)
0.255±0.015*
(6.477±0.381)
0.400*
(10.160)
MAX
1 2 3 4
8 7 6 5
0.130±0.005
(3.302±0.127)
0.018±0.003
(0.457±0.076)
0.100±0.010
(2.540±0.254)
(8.255 )
+0.635
-0.381
0.325
+0.025
-0.015
0.009-0.015
(0.229-0.381)
0.300-0.325
(7.620-8.255)
0.065
(1.651)
TYP
0.005 (0.127)
MIN
0.125 (3.175)
MIN
0.015
(0.380)
MIN
*DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS. MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.010" (0.254mm)
P (8L PDIP ) AMS DRW# 042294
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