LP2951ACP-3 [ADMOS]
100mA LOW DROPOUT VOLTAGE REGULATOR; 100mA时的低压差稳压器
| 型号： | LP2951ACP-3 |
| 厂家： | 
ADVANCED MONOLITHIC SYSTEMS |
| 描述： | 100mA LOW DROPOUT VOLTAGE REGULATOR |
| 文件： | 总14页 (文件大小：145K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Advanced
Monolithic
Systems
LP2950/LP2951
100mA LOW DROPOUT VOLTAGE REGULATOR
FEATURES
APPLICATIONS
· 5V, 3.3V, and 3V Versions at 100mA Output Current
· High Accuracy Output Voltage
· Extremely Low Quiescent Current
· Battery Powered Systems
· Portable Consumer Equipment
· Cordless Telephones
· Low Dropout Voltage
· Extremely Tight Load and Line Regulation
· Very Low Temperature Coefficient
· Portable (Notebook) Computers
· Portable Instrumentation
· Radio Control Systems
· Automotive Electronics
· Avionics
· Current and Thermal Limiting
· Needs Minimum Capacitance (1mF) for Stability
· Unregulated DC Positive Transients 60V
ADDITIONAL FEATURES (LP2951 ONLY)
· 1.24V to 29V Programmable Output
· Error Flag Warning of Voltage Output Dropout
· Logic Controlled Electronic Shutdown
· Low-Power Voltage Reference
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
PACKAGE TYPE
PIN CONNECTION
8L SOIC/ 8L PDIP
OPERATING
TEMP. RANGE
IND.
OUTPUT
SENSE
1
2
3
4
8
7
6
5
INPUT
TO-92
8 LEAD PDIP 8 LEAD SOIC
FEEDBACK
VTAP
LP2950ACN-X LP2951ACP-X LP2951ACS-X
SHUTDOWN
GROUND
LP2950CN-X
LP2951CP-X
LP2951CS-X
IND
ERROR
X = 3.3V, or 3V
Top View
TO-92
OUTPUT
GND
INPUT
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
4 seconds, 240°C
4 seconds, 219°C
TBD
SHUTDOWN Input Voltage,
Error Comparator Output
Voltage,(Note 9)
Infrared
Vapor Phase
ESD
FEEDBACK Input Voltage
(Note 9) (Note 10)
-1.5 to +30V
OPERATING RATINGS (Note 1)
Power Dissipation
Junction Temperature
Storage Temperature
Internally Limited
+150°C
-65°C to +150°C
Max. Input Supply Voltage
Junction Temperature Range
(TJ) (Note 8)
30V
Soldering Dwell Time, Temperature
LP2950AC-XX, LP2950C-XX
LP2951AC-XX, LP2951C-XX
-40°C to +125°C
ELECTRICAL CHARACTERISTICS at V =Vout+1V, Ta=25°C, unless otherwise noted.
s
LP2950AC
LP2950C
Parameter
Conditions
LP2951AC
LP2951C
Units
(Note 2)
Min.
2.985
Typ.
Max.
3.015
Min.
2.970
Typ.
Max.
3.030
3 V Versions (Note 16)
T = 25°C
(Note 3)
J
Output Voltage
3.0
3.0
3.0
3.0
3.0
3.0
V
V
V
-25°C £T £85°C
J
2.970
3.030
2.955
3.045
Full Operating Temperature Range
2.964
3.036
2.940
3.060
100 mA £I £100 mA
L
Output Voltage
3.0
3.0
V
2.958
3.042
2.928
3.072
T £T
J
JMAX
3.3 V Versions (Note 16)
T = 25°C
J
(Note 3)
Output Voltage
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
-25°C £T £85°C
J
Full Operating Temperature Range
100 mA £I £100 mA
L
Output Voltage
3.3
3.3
V
3.254
3.346
3.221
3.379
T £T
J
JMAX
5 V Versions (Note 16)
T = 25°C
J
(Note 3)
Output Voltage
4.975
4.95
4.94
5.0
5.0
5.0
5.025
4.95
4.925
4.90
5.0
5.0
5.0
5.05
5.075
5.10
V
V
V
-25°C £T £85°C
J
5.050
Full Operating Temperature Range
5.06
100 mA £I £100 mA
L
Output Voltage
5.0
5.0
V
4.925
5.075
4.88
5.12
T £T
J
JMAX
All Voltage Options
Output Voltage
Temperature Coefficient
ppm/°C
20
50
(Note 12) (Note 4)
6V £V £30V (Note 15)
Line Regulation (Note 14)
Load Regulation (Note 14)
0.03
0.04
0.1
0.1
0.04
0.1
0.2
0.2
%
%
in
100 mA £I £ 100 mA
L
I
I
= 100m A
Dropout Voltage
(Note 5)
50
80
50
80
mV
mV
L
L
= 100 mA
380
450
380
450
I
I
= 100 mA
L
L
Ground Current
75
8
120
12
75
8
120
12
mA
= 100 mA
mA
Current Limit
V
= 0
160
200
0.2
160
200
0.2
mA
out
Thermal Regulation
(Note 13)
0.05
0.05
%/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)
LP2950AC
LP2950C
LP2951C
PARAMETER
CONDITIONS
LP2951AC
Units
(Note 2)
Min.
Typ.
Max.
Min.
Typ.
430
160
100
Max.
C
C
C
= 1mF
L
L
L
Output Noise,
430
160
100
mV rms
mV rms
mV rms
= 200 mF
= 13.3 mF
10Hz to 100KHz
(Bypass = 0.01 mF pins 7 to
1(LP2951))
8-Pin Versions only
LP2951AC
LP2951C
Reference Voltage
Reference Voltage
1.22
1.235
1.25
1.21
1.235
1.26
V
V
Over Temperature (Note 7)
1.19
1.27
1.185
1.285
Feedback Pin Bias Current
40
20
60
40
60
nA
Reference Voltage Temperature
Coefficient
50
ppm/°C
( Note 12 )
Feedback Pin Bias Current
Temperature Coefficient
Error Comparator
0.1
0.1
nA/°C
Output Leakage Current
V
= 30V
0.01
150
1
0.01
150
1
mA
OH
V
I
= 4.5V
Output Low Voltage
in
250
250
mV
= 400mA
OL
(Note 6)
(Note 6)
(Note 6)
40
60
75
15
40
60
75
15
mV
mV
mV
Upper Threshold Voltage
Lower Threshold Voltage
95
95
Hysteresis
Shutdown Input
Low (Regulator ON)
High (Regulator OFF)
1.3
1.3
V
V
0.7
0.7
Input logic Voltage
2
2
Vs = 2.4V
30
50
30
50
mA
mA
Shutdown Pin Input Current
(Note 3)
V = 30V
s
450
600
450
600
Regulator Output Current in
Shutdown (Note 3)
(Note 11)
3
10
3
10
mA
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 mA and CL = 1 mF for 5V versions and 2.2mF 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, 100mA£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 ³ 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.
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 mA 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
VOUT
100mA
I
£
UNREGULATED DC
L
UNREGULATED DC
7
8
1
+
FEED-
+
INPUT
OUTPUT
BACK
INPUT
VOUT
IL£ 100mA
2
OUTPUT
SENSE
+
-
+
-
SEE APPLICATION
HINTS
+
3
6
ERROR
AMPLIFIER
FROM
CMOS
OR TTL
SHUT-
DOWN
ERROR
AMPLIFIER
VTAP
+
SEE APPLICATION
HINTS
330k
W
5
+
+
-
TO CMOS
OR TTL
50mV
ERROR
4
+
1.23V
REFERENCE
+
1.23V
GROUND
REFERENCE
GROUND
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
Quiescent Current
Dropout Characteristics
Input Current
10
1
6
5
4
250
225
5V OUTPUT
5V OUTPUT
200
175
150
RL= 50 kW
RL= 50 kW
125
100
3
2
RL= 50W
RL= ¥
0.1
75
50
1
25
0
0
0.01
1
2
3
4
5
6
0
1
2
3
4
5
6
7
8
9 10
0.1
1
10
100
0
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LOAD CURRENT (mA)
Temperature Drift of 3
Representative Units
Input Current
Quiescent Current
120
110
100
5.06
160
140
120
100
80
5V OUTPUT
5V OUTPUT
5V OUTPUT
RL= 50W
5.04
5.02
90
80
70
IL= 1 mA
60
50
40
30
20
10
5.0
IL= 0
60
4.98
40
0.2%
4.96
4.94
20
0
0
0
1
2
3
4
5
6
7
8
9
10
-75 -50 -25
0
25 50 75 100 125 150
0
1
2
3
4
5
6
7
8
INPUT VOLTAGE (V)
TEMPERATURE (° C)
INPUT VOLTAGE (V)
Quiescent Current
Quiescent Current
Quiescent Current
120
110
100
90
10
9
8
5V OUTPUT
5V OUTPUT
IL= 100mA
5V OUTPUT
7
6
5
4
3
2
1
0
VIN= 6V
IL= 100mA
V
IN= 6V
IL= 100mA
80
8
7
70
60
50
-75
-50 -25
0
25 50 75 100 125 150
-50 -25
-75
0
25 50 75 100 125 150
0
1
2
3
4
5
6
7
8
TEMPERATURE (° C)
TEMPERATURE (° C)
INPUT VOLTAGE (V)
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Dropout Voltage
Short Circuit Current
Dropout Voltage
170
160
150
140
130
120
110
100
600
500
400
300
500
400
300
IL= 100mA
~
~
200
100
50
0
TJ = 25°C
100
IL= 100mA
0
-75 -50 -25
0
25 50 75 100 125 150
-75 -50 -25
0
25 50 75 100125 150
100mA
1mA
10mA
100mA
TEMPERATURE (° C)
TEMPERATURE (° C)
OUTPUT CURRENT
LP2951 Minimum Operating Voltage
LP2951 Feedback Bias Current
LP2951 Feedback Pin Current
20
10
50
2.2
2.1
PIN 7 DRVEN BY EXTERNAL
SOURCE (REGULATOR RUN
OPEN LOOP)
0
-50
2.0
1.9
0
TA = 125°C
-100
-10
-150
-200
-250
1.8
1.7
TA = 25°C
-20
-30
TA = -55°C
1.6
-75
125
0
0.5
0
100 150
125
-75 -50 -25
0
25 50 75 100
150
-2.0 -1.5 -1.0 -0.5
1.0
-50 -25
25 50 75
TEMPERATURE (° C)
TEMPERATURE (° C)
FEEDBACK VOLTAGE (V)
LP2951 Error Comparator Output
LP2951 Comparator Sink Current
Line Transient Response
100
mV
50
9
8
2.5
VOUT= 5V
TA = 125°C
mV
2.0
1.5
1.0
0.5
0.0
7
6
5
50k RESISTOR TO
EXTERNAL 5V SUPPLY
0
CL= 1mF
-50
mV
TA = 25°C
TA = -55°C
IL= 1mA
HYSTERESIS
4
3
2
1
0
VOUT= 5V
~
~
8V
6V
50k
RESISTOR
TO VOUT
4V
0
1
2
3
4
5
6
7
8
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
OUTPUT LOW VOLTAGE (V)
0
200
400
600
800
INPUT VOLTAGE (V)
TIME (ms)
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
Load Transient Response
LP2951 Enable Transient
250
200
150
100
50
80
60
40
20
0
7
6
CL= 1 mF
5
4
IL= 10 mA
VIN = 8V
3
VOUT = 5V
0
-20
-40
-60
CL= 10 mF
VOUT = 5V
2
1
CL= 10 mF
-50
-100
CL= 1 mF
0
2
VOUT = 5V
~
~
~
~
~
~
100
100
mA
mA
0
100
100
m
m
A
A
-2
-100
0
1
2
3
4
5
0
4
8
12
16
20
106
105
0
100 200 300 400 500 600 700
m
TIME ( s)
TIME (ms)
TIME (ms)
Ripple Rejection
Ripple Rejection
Output Impedance
90
80
70
60
50
40
30
20
90
80
70
60
50
40
30
20
10
5
IO= 100mA
2
1
CL= 1 mF
VIN= 6V
VOUT = 5V
IO= 100mA
IL= 1mA
IO= 1 mA
IL= 0
0.5
0.2
0.1
VOUT = 5V
CL= 1 mF
IL= 100mA
CL= 1 mF
VIN= 6V
0.05
VOUT = 5V
0.02
0.01
IL= 10mA
106
105
105
102
103
104
102
103
104
101
101
10
100
1K
10K 100K 1M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
Ripple Rejection
LP2951 Output Noise
LP2951 Divider Resistance
80
70
60
50
40
30
20
10
400
300
3.5
5V OUTPUT
IL= 100mA
IL= 50mA
3.0
2.5
2.0
CL= 1 mF
IL= 100mA
200
100
0
CL= 220 mF
CL= 1mF
1.5
1.0
CL= 3.3 mF
VIN= 6V
VOUT= 5V
0.01 mF
0.5
0.0
BYPASS
PIN 1 TO
PIN 7
105
FREQUENCY (Hz)
102
103
104
106
102
103
104
-75 -50 -25
0 25 50 75 100 125 150
TEMPERATURE (° C)
101
FREQUENCY (Hz)
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
LP2951 Maximum Rated
Output Current
Shutdown Treshold Voltage
Line Regulation
1.8
30
25
120
8 PIN MOLDED
DIP SOLDERED
TO PC BOARD
20
15
10
5
IL= 100mA
100
1.6
1.4
TJMAX= 125° C
REGULATOR OFF
VOUT = 5V
80
TJ = 150° C
IL= 1mA
TA= 25° C
1.2
1.0
0
60
~
~
TA= 50° C
REGULATOR ON
10
40
IL= 100mA
TJ = 125° C
5
0
-5
20
0.8
0.6
TA= 85° C
0
-10
-75 -50 -25
0
25 50 75 100 125
5
10
15
20
25
10
5
INPUT VOLTAGE (V)
30
150
30
0
15
20
25
TEMPERATURE (° C)
INPUT VOLTAGE (V)
LP2950 Maximum Rated
Output Current
Thermal Response
120
5
4
TO-92 PACKAGE
.25"LEADS SOLDERED
TO PC BOARD
100
80
2
0
TJMAX= 125° C
60
-2
1
TA= 25° C
~
~
40
20
0
1.25W
TA= 85° C
0
-1
10
5
INPUT VOLTAGE (V)
30
0
10
20
30
40
50
0
15
20
25
TIME (ms)
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
LP2950/LP2951
APPLICATION HINTS
External Capacitors
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 400mA, this sink current adds to
battery drain in a low battery condition. Suggested values range
from 100K to 1MW. The resistor is not required if this output is
unused.
A 1.0 mF 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 (2.2m 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 W 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.
Programming the Output Voltage (LP2951)
At lower values of output current, less output capacitance is
required for stability. The capacitor can be reduced to 0.33 mF for
currents below 10 mA or 0.1 mF 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 3.3mF (or greater)
capacitor should be used.
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:
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 1mA is
recommended.
A 1mF 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 mF will fix this problem.
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 mA forces an upper limit of 1.2
MW 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 mA. Since the LP2951 typically draws 60
mA at no load with Pin 2 open-circuited, this is a small price to
pay.
Reducing Output Noise
Error Detection Comparator Output
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 mF to 220 mF only decreases the noise from 430
mV to 160 mV rms for a 100 kHz bandwidth at 5V 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.
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 / 2pR1 ´ 200 Hz
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 ).
or about 0.01 mF. When doing this, the output capacitor must be
increased to 3.3 mF to maintain stability. These changes reduce
the output noise from 430 mV to 100 mV 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)
+VIN
4.75V
OUTPUT
VOLTAGE
8
+VIN
ERROR*
100k
VOUT
1.2
30V
5
3
1
ERROR
OUPUT
ERROR*
VOUT
LP2951
*
+
**SHUTDOWN
INPUT
3.3mF
SD
GND
R1
.01
mF
5V
INPUT
VOLTAGE
FB
4
7
1.23V
VREF
1.3V
R2
FIGURE 1. ERROR Output Timing
FIGURE 2. Adjustable Regulator
*See Application Hints.
*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 k suggested), to ensure
a low-level logic signal during any fault condition, while still
allowing a valid high logic level during normal operation.
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
330W
8
6
1
2
IN
OUT
2N5432 (2)
8
+VIN
27
W
k
LP2951
*VOUT » VIN
5
3
1
ERROR
OUPUT
VOUT
ERROR
5V OUTPUT
VTAP
SENSE
LP2951
LOAD
50mA TO
300mA
SHUTDOWN
INPUT
FB
GND
SD
GND
4.7mF
7
4
FB
4
7
*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
30V
+V = 2
LOAD
IL
5V BUS
+VIN
8
VIN
1
LP2950 -5.0
VOUT
*VOUT » 5V
VOUT
LP2951
3
SHUTDOWN
INPUT
SD
0.1mF
1mF
GND
GND
FB
4
7
+
R
1%
1mF
*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
4.7kW
*SLEEP
INPUT
4
20mA
*OUTPUT
5
1
2
8
47kW
470kW
+VIN
8
1
7
VOUT
+VIN
+VOUT
LP2951
4
5
3
1
ERROR
OUPUT
VOUT
ERROR
1N4001
FB
LP2951
200kW
SHUTDOWN
INPUT
GND
4
SD
GND
100pF
+
1%
3.3mF
0.1mF
2N3906
360
FB
1N457
100kW
4
7
1%
MIN. VOLTAGE » 4V
100kW
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
+VIN
CURRENT
+VIN = VOUT +.5V
LIMIT SECTION
D1
8
2
+VIN
0.05
SENSE
5V MEMORY
SUPPLY
680
D2
6
7
1
VTAP
FB
VOUT
LP2951
#1
20
5
470
+
ERROR
1mF
3.6V
NICAD
GND
4
MJE2955
2N3906
4.7MW
+VOUT @ 2A
10kW
8
+VIN
ERROR
27 kW
ERROR
FLAG
5
+
+
100mF
EARLY WARNING
R1
D3
4.7
2.7MW
LP2951
TANT.
7
3
D4
SD
FB
VOUT
1%
R2
GND
220
Q1
8
2
4
1
RESET
mP
330 kW
SENSE
+VIN
20kW
6
MAIN 5V OUTPUT
.033
VDD
VTAP
FB
VOUT
7
3
LP2951
#2
5
+
SD
ERROR
1mF
GND
4
VOUT = 1.23V(1+R1/R2)
·
·
·
Early warning flag on low input voltage
Main output latches off at lower input voltages
Battery backup on auxiliary output
For 5V VOUT, use internal resistors. Wire pin 6 to 7 and pin 2 to +VOUTBuss.
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
10k
W
0.01mF
1mF
SUPERTEX
VP12C
470kW
8
VOUT
+VIN
ERROR
8
5
3
1
7
VOUT
IN
OUTPUT
5V ± 1% @
0 TO 1A
470kW
2
1
6
7
VTAP
SENSE
OUT
LP2951
R1
R2
+
220m
F
LP2951
+
SD
FB
1mF
RESET
GND
4
FB
GND
4
2kW
1MW
0.002mF
IQ @ 400mA
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)
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)
10°
NOM
5° NOM
0.500
(12.70)
MIN
UNCONTROLLED
LEAD DIMENSIONS
0.050
(1.270)
MAX
0.015±0.002
N (TO-92 ) AMS DRW# 042391
(0.381±0.051)
0.016±0.003
(0.406±0.076)
0.050±0.005
(1.270±0.127)
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
(0.254-0.508)
x 45°
0.053-0.069
(1.346-1.752)
0.004-0.010
(0.101-0.254)
0.008-0.010
(0.203-0.254)
0°-8° TYP
0.014-0.019
(0.355-0.483)
0.050
(1.270)
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. 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)
0.400*
(10.160)
MAX
8
7
6
5
0.255±0.015*
(6.477±0.381)
1
2
3
4
0.300-0.325
(7.620-8.255)
0.130±0.005
(3.302±0.127)
0.045-0.065
(1.143-1.651)
0.065
(1.651)
TYP
0.009-0.015
0.125
(3.175)
MIN
(0.229-0.381)
0.005
(0.127)
MIN
0.015
(0.380)
MIN
+0.025
-0.015
+0.635
0.325
0.100±0.010
(2.540±0.254)
0.018±0.003
(0.457±0.076)
(8.255
)
-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. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
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