LP2951-03BM [MICREL]
100mA Low-Dropout Voltage Regulator; 100mA时的低压差稳压器
| 型号： | LP2951-03BM |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | 100mA Low-Dropout Voltage Regulator |
| 文件： | 总14页 (文件大小：137K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LP2950/2951
100mA Low-Dropout Voltage Regulator
General Description
Features
The LP2950 and LP2951 are micropower voltage regulators
with very low dropout voltage (typically 40mV at light loads
and 380mV at 100mA), and very low quiescent current (75µA
typical). The quiescent current of the LP2950/LP2951
increases only slightly in dropout, thus prolonging battery life.
This feature, among others, makes the LP2950 and LP2951
ideally suited for use in battery-powered systems.
•
•
•
•
•
•
•
•
High accuracy 5V, guaranteed 100 mA output
Extremely low quiescent current
Low-dropout voltage
Extremely tight load and line regulation
Very low temperature coefficient
Use as regulator or reference
Needs only 1µF for stability
Current and thermal limiting
Available in a 3-Pin TO-92 package, the LP2950 is pin-
compatible with the older 5V regulators. Additional system
functions, such as programmable output voltage and logic-
controlled shutdown, are available in the 8-pin DIP and 8-pin
SOIC versions of the LP2951.
LP2951 Versions Only
•
•
•
Error flag warns of output dropout
Logic-controlled electronic shutdown
Output programmable from 1.24 to 29V
Applications
3
•
•
Automotive Electronics
Voltage Reference
•
Avionics
Block Diagram and Pin Configurations
UNREGULATED DC
5V
150 mA
MAX.
7
8
1
OUTPUT
+
FEEDBACK
INPUT
2
SENSE
182
+
–
6
5V TAP
5
kΩ
3
ERROR
330
FROM
AMPLIFIER
SHUT-
CMOS
+
kΩ
1.5 µF
DOWN
60 mV
+
60
kΩ
OR TTL
+
–
TO CMOS
OR TTL
ERROR
4
ERROR
DETECTION
+
1.23 V
REF.
COMPARATOR
GROUND
LP2950 and LP2951 Block Diagram
(Pin Numbers Refer to LP2951)
1
8
INPUT
OUTPUT
SENSE
3
2
1
2
3
4
7
6
5
FEEDBACK
SHUTDOWN
GROUND
5V TAP
ERROR
OUTPUT
INPUT
GROUND
DIP and SO Packages
(BN and BM)
TO-92 Plastic Package Bottom View
(BZ)
See MIC2950 for a part with 1) higher output (150 mA), 2) transient protection (60V), and 3) reverse input protection to –20V)
February 1999
3-35
LP2950/2951
Micrel
Additional features available with the LP2951 also include an from–40°Cto+125°C;the-02versionhasatighteroutputand
error flag output that warns of a low output voltage, which is reference voltage specification range over temperature. The
often due to failing batteries on the input. This may also be LP2951 is available as an -02 or -03 version.
used as a power-on reset. A logic-compatible shutdown input
The LP2950 and LP2951 have a tight initial tolerance (0.5%
isalsoavailablewhichenablestheregulatortobeswitchedon
typical), a very low output voltage temperature coefficient
and off. This part may also be pin-strapped for a 5V output,
which allows use as a low-power voltage reference, and
orprogrammedfrom1.24Vto29Vwiththeuseoftwoexternal
extremely good load and line regulation (0.05% typical). This
resistors.
greatly reduces the error in the overall circuit, and is the result
The LP2950 is available as either an -02 or -03 version. The of careful design techniques and process control.
-02and-03versionsareguaranteedforjunctiontemperatures
Ordering Information
Part Number
LP2950-02BZ
LP2950-03BZ
LP2951-02BM
LP2951-03BM
LP2951-02BN
LP2951-03BN
LP2951-4.8BM
Voltage
5.0V
Temperature Range*
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
Package
3-Pin TO-92 plastic
3-Pin TO-92 plastic
8-Pin SOIC
Accuracy
0.5%
5.0V
1.0%
5.0V
0.5%
5.0V
8-Pin SOIC
1.0%
5.0V
8-Pin Plastic DIP
8-Pin Plastic DIP
8-Pin SOIC
0.5%
5.0V
1.0%
4.85V
1.0%
* Junction temperatures
Absolute Maximum Ratings
If Military/Aerospace specified devices are required, contact your local
Micrel representative/distributor for availability and specifications.
Power dissipation
Internally Limited
260°C
Lead Temperature (Soldering, 5 seconds)
Storage Temperature Range
–65°C to +150°C
Operating Junction Temperature Range (Note 8)
LP2950, LP2951
–40°C to +125°C
Input Supply Voltage
–0.3V to +30V
Feedback Input Voltage (Notes 9 and 10)
Shutdown Input Voltage (Note 9)
–1.5V to +30V
–0.3V to +30V
–0.3V to +30V
Error Comparator Output Voltage (Note 9)
ESD Rating is to be determined.
3-36
February 1999
LP2950/2951
Micrel
Electrical Characteristics Note 1 TA = 25°C except as noted.
Parameter
Condition
Min
Typ
Max
Units
V
Output Voltage
TJ = 25°C
LP295x-02 (±0.5%)
4.975 5.000 5.025
4.950 5.000 5.050
4.802 4.850 4.899
LP295x-03 (±1%)
V
LP2951-4.8 (±1%)
V
Output Voltage
–25°C ≤ TJ ≤ +85°C
LP295x-02 (±0.5%)
4.950
4.925
4.777
4.940
4.900
4.753
4.930
4.880
4.733
5.050
5.075
4.872
5.060
5.100
4.947
5.070
5.120
4.967
V
LP295x-03 (±1%)
V
LP2951-4.8 (±1%)
V
Output Voltage
Over Full Temperature Range
LP295x-02 (±0.5%), –40°C to +125°C
LP295x-03 (±1%), –40°C to +125°C
LP2951-4.8 (±1%), –40°C to +125°C
LP295x-02 (±0.5%), 100µA ≤ IL ≤ 100mA, TJ ≤ TJ(max)
LP295x-03 (±1%), 100µA ≤ IL ≤ 100mA, TJ ≤ TJ(max)
LP2951-4.8 (±1%), 100µA ≤ IL ≤ 100mA, TJ ≤ TJ(max)
LP295x-02 (±0.5%), Note 12
LP295x-03 (±1%), Note 12
V
V
V
Output Voltage
Over Load Variation
V
V
V
Output Voltage
Temperature Coefficient
20
50
100 ppm/°C
150 ppm/°C
150 ppm/°C
3
LP2951-4.8 (±1%), Note 12
LP295x-02 (±0.5%), Notes 14, 15
50
Line Regulation
0.03
0.10
0.20
%
%
LP295x-03 (±1%), Notes 14, 15
LP2951-4.8 (±1%), Notes 14, 15
LP295x-02 (±0.5%), Note 14, 100µA ≤ IL ≤ 100mA
LP295x-03 (±1%), Note 14, 100µA ≤ IL ≤ 100mA
LP2951-4.8 (±1%), Note 14, 100µA ≤ IL ≤ 100mA
Note 5, IL = 100µA
0.04
0.04
0.04
0.10
0.10
50
0.20
0.40
%
%
0.20
0.40
%
%
Load Regulation
0.10
0.20
%
%
0.20
0.30
%
%
0.20
0.30
%
%
Dropout Voltage
Ground Current
Dropout Current
80
150
mV
mV
Note 5, IL = 100mA
380
100
8
450
600
mV
mV
IL = 100µA
150
200
µA
µA
IL = 100mA
12
14
mA
mA
VIN = 4.5V, IL = 100µA
180
250
310
µA
µA
February 1999
3-37
LP2950/2951
Micrel
Parameter
Condition
OUT = 0V
Min
Typ
Max
Units
Current Limit
V
160
200
220
mA
mA
Thermal Regulation
Output Noise
Note 13
0.05
430
160
100
0.20
%/W
10Hz to 100kHz, CL = 1µF
10Hz to 100kHz, CL = 200µF
µVRMS
µVRMS
µVRMS
10Hz to 100kHz, CL = 3.3µF,
0.01µF bypass Feedback to Output
Reference Voltage
Reference Voltage
LP295x-02 (±0.5%)
LP295x-03 (±1%)
LP2951-4.8 (±1%)
1.220 1.235 1.250
1.200 1.260
V
V
1.210 1.235 1.260
1.200 1.270
V
V
1.210 1.235 1.260
V
V
1.200
1.190
1.185
1.185
1.270
1.270
1.285
1.285
LP295x-02 (±0.5%), Note 7
LP295x-03 (±1%), Note 7
LP2951-4.8 (±1%), Note 7
V
V
V
Feedback Bias Current
Reference Voltage
20
40
60
nA
nA
LP295x-02 (±0.5%), Note 12
LP295x-03 (±1%), Note 12
LP2951-4.8 (±1%), Note 12
20
50
50
0.1
ppm/°C
ppm/°C
ppm/°C
nA/°C
Feedback Bias Current
Temperature Coefficient
Output Leakage Current
Output Low Voltage (Flag)
Upper Threshold Voltage
Lower Threshold Voltage
V
OH = 30V
0.01
150
60
1.00
2.00
µA
µA
VIN = 4.5V, IOL = 200µA
250
400
mV
mV
Note 6
Note 6
Note 6
40
25
mV
mV
75
95
140
mV
mV
Hysteresis
15
mV
Input Logic Voltage
LP295x-02 (±0.5%)
Low
High
1.3
V
V
V
0.7
0.7
0.7
2.0
2.0
2.0
LP295x-03 (±1%)
Low
High
1.3
1.3
V
V
V
LP2951-4.8 (±1%)
Low
High
V
V
V
3-38
February 1999
LP2950/2951
Micrel
Parameter
Condition
Min
Typ
Max
Units
Shutdown Input Current
VSHUTDOWN = 2.4V
30
50
100
µA
µA
V
SHUTDOWN = 30V
450
3
600
750
µA
µA
Regulator Output Current
in Shutdown
Note 11
10
20
µA
µA
Note 1: Boldface limits apply at temperature extremes.
Note 2: Unless otherwise specified all limits guaranteed for T = 25°C, V = 6V, I = 100µA and C = 1µF. Additional conditions for the 8-pin versions
J
IN
L
L
are Feedback tied to 5V Tap and Output tied to Output Sense (V
= 5V) and V
≤ 0.8V.
OUT
SHUTDOWN
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 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
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 6V input. To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = V
/V
=
OUT
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/1.235V = 384mV. Thresholds remain constant as a percent of V
typically 5% below nominal, 7.5% guaranteed.
as V
is varied, with the dropout warning occurring at
OUT
OUT
Note 7:
V
≤ V
≤ (V – 1 V), 2.3V ≤ V ≤ 30V, 100µA < I ≤ 100mA, T ≤ T
.
REF
OUT
IN
IN
L
J
JMAX
Note 8: The junction-to-ambient thermal resistance of the TO-92 package is 180°C/W with 0.4” leads and 160°C/W with 0.25” leads to a PC board.
The thermal resistance of the 8-pin DIP package is 105°C/W junction-to-ambient when soldered directly to a PC board. Junction-to-ambient
thermal resistance for the SOIC (M) package is 160°C/W.
3
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
≥ 2V, V ≤ 30 V, V
= 0, with Feedback pin tied to 5V Tap.
SHUTDOWN
IN
OUT
Note 12: Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
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 V = 30V (1.25W pulse) for t = 10ms.
IN
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 in the specification for thermal regulation.
Note 15: Line regulation for the LP2951 is tested at 150°C for I = 1mA. For I = 100µA and T = 125°C, line regulation is guaranteed by design to
L
L
J
0.2%. See Typical Performance Characteristics for line regulation versus temperature and load current.
February 1999
3-39
LP2950/2951
Micrel
Typical Performance Characteristics
Quiescent Current
Dropout Characteristics
Input Current
10
1
6
250
225
200
175
150
125
100
75
5
4
RL = 50kΩ
RL = 50kΩ
3
2
RL
=
∞
RL = 50
Ω
0.1
50
1
0
25
0
0.01
0.1
1
10
150
0
1
2
3
4
5
6
0
1
2
3
4
5
6
7
8 9 10
LOAD CURRENT (mA)
INPUT VOLTAGE (VOLTS)
INPUT VOLTAGE (VOLTS)
Output Voltage vs.
Temperature of 3
Representative Units
Input Current
Ground Current
160
150
140
130
120
110
100
90
5.06
5.04
5.02
5.0
320
280
240
RL = 50
Ω
IL = 1 mA
IL = 0
200
160
80
70
60
50
40
30
20
10
0 0
120
4.98
4.96
4.94
80
40
0
0.2%
1
2
3
4
5
6
7
8
9
10
-75 -50 -25 0 25 50 75 100125 150
0
1
2
3
4
5
6
7
8
INPUT VOLTAGE (VOLTS)
TEMPERATURE (°C)
INPUT VOLTAGE (VOLTS)
Quiescent Current
Ground Current
Ground Current
16
240
220
16
14
12
10
8
IL = 100 mA
12
8
VIN = 6V
IL = 100 µA
VIN = 6V
IL = 100 mA
200
180
6
4
2
0
4
0
1
2
3
4
5
6
7
8
-75 -50 -25
0
25 50 75 100 125 150
-75 -50 -25 0 25 50 75 100125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
INPUT VOLTAGE (V)
Short Circuit Current
Drop-out Voltage
Drop-out Voltage
500
400
300
200
100
170
160
150
140
600
IL = 100 mA
500
400
300
100
50
130
120
110
100
T = 25 °C
J
IL = 100 µA
0
0
-75 -50 -25
0
25 50 75 100 125 150
-75 -50 -25 0 25 50 75 100125 150
100 µA 1 mA
10 mA
100 mA
TEMPERATURE (°C)
TEMPERATURE (°C)
OUTPUT CURRENT
3-40
February 1999
LP2950/2951
Micrel
LP2951
Minimum Operating Voltage
LP2951
Feedback Bias Current
LP2951
Feedback Pin Current
2.2
50
0
20
10
0
PIN 7 DRIVEN BY EXTERNAL
SOURCE (REGULATOR RUN
OPEN LOOP)
2.1
2.0
1.9
1.8
-50
T = 125°C
A
-100
-10
-20
-30
-150
-200
-250
T = 25°C
A
1.7
1.6
T = –55°C
A
-75 -50 -25 0 25 50 75 100125 150
-75 -50 -25 0 25 50 75 100125 150
-2.0 -1.5 -1.0 -0.5
0
0.5 1.0
TEMPERATURE (°C)
TEMPERATURE (°C)
FEEDBACK VOLTAGE (V)
LP2951
LP2951
Error Comparator Output
Comparator Sink Current
Line Transient Response
100
mV
50
mV
8
2.5
VOUT = 5V
T = 125°C
A
6
2.0
1.5
1.0
0.5
0.0
0
3
4
T = 25°C
A
-50
mV
CL= 1 µF
IL = 1 mA
VOUT = 5V
HYSTERESIS
2
8V
T = -55°C
A
0
6V
4V
PULLUP RESISTOR TO
SEPARATE 5V SUPPLY
-2
0
1
2
3
4
5
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
200 400
600 800
INPUT VOLTAGE (V)
OUTPUT LOW VOLTAGE (V)
TIME (µs)
LP2951
Load Transient Response
Load Transient Response
Enable Transient
80
60
40
20
0
-20
-40
-60
250
200
150
100
50
7
6
LL= 1 µF
5
4
3
0
IL = 10 mA
IN = 8V
2
1
-50
-100
CL= 10 µF
VOUT = 5V
V
CL = 10 µF VOUT = 5V
CL= 1 µF
VOUT = 5V
0
100
mA
100
µA
100
mA
100
µA
2
0
-2
-100
0
100 200 300 400 500 600 700
0
1
2
3
4
5
0
4
8
12 16 20
TIME (ms)
TIME (ms)
TIME (µs)
Output Impedance
Ripple Rejection
Ripple Rejection
10
5
90
80
70
60
50
90
80
I0 = 100 µA
CL = 1 µF
IN = 6V
OUT = 5V
I0 = 1 mA
2
1
V
V
70
60
IL = 1 mA
I0 = 100 mA
IL = 0
0.5
0.2
0.1
50
40
30
20
VOUT = 5V
CL= 1 µF
40 CL = 1 µF
IL = 100 µA
0.05
VIN = 6V
30
20
VOUT = 5V
0.02
0.01
IL = 10 mA
101
102 103 104 10
106
101
102 103 104 105 106
FREQUENCY (Hz)
10 100
1K 10K 100K 1M
FREQUENCY (Hz)
FREQUENCY (Hz)
February 1999
3-41
LP2950/2951
Micrel
Typical Performance Characteristics (Continued)
Ripple Rejection
Output Noise
LP2951 Divider Resistance
80
70
60
50
40
30
20
10
3.5
3.0
2.5
2.0
1.5
1.0
400
300
200
100
0
IL = 50 µA
IL = 100 mA
CL = 1 µF
IL = 100 mA
CL = 1 µF
CL = 220 µF
CL
=
3.3 µF
VIN = 6V
VOUT = 5V
0.01 µF
0.5 BYPASS
PIN 1 TO
PIN 7
0.0
101 102 103 104 105 106
FREQUENCY (Hz)
102
103
104
105
-75 -50-25
0 25 50 75 100125 150
FREQUENCY (Hz)
TEMPERATURE (°C)
LP2950 Maximum
Rated Output Current
Shutdown Threshold Voltage
Line Regulation
1.8
30
25
20
15
10
5
120
8-PIN MOLDED
DIP SOLDERED
TO PC BOARD
IL = 100 µA
1.6
1.4
1.2
1.0
0.8
0.6
100
80
60
40
20
0
T
= 125°C
J
MAX
TJ = 150°C
TJ = 125°C
VOUT = 5V
TA = 25°C
IL = 1 mA
0
TA = 50°C
TA = 85°C
10
5
0
-5
-10
IL = 100 µA
-75 -50-25
0 25 50 75 100125 150
5
10
15
20
25
30
0
5
10 15 20 25
30
TEMPERATURE (°C)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
LP2950 Maximum
Rated Output
Thermal Response
120
100
80
5
4
TO-92 PACKAGE
0.25" LEADS SOLDERED
TO PC BOARD
2
T
= 125°C
J
0
MAX
60
-2
1
TA = 25°C
40
1.25W
TA = 85°C
20
0
0
-1
0
5
10 15 20 25 30
0
10
20
30
40
50
INPUT VOLTAGE (V)
TIME (µs)
3-42
February 1999
LP2950/2951
Micrel
which VOUT = 4.75V). 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
(approximately 4.75V) does not vary with load.
Applications Information
External Capacitors
A1.0µF(orgreater)capacitorisrequiredbetweentheLP2950/
LP2951 output and ground to prevent oscillations due to
instability. Most types of tantalum or aluminum electrolytics
will be adequate; film types will work, but are costly and
therefore not recommended. Many aluminum electrolytics
haveelectrolytesthatfreezeatabout–30°C,sosolidtantalum
capacitorsarerecommendedforoperationbelow–25°C. The
important parameters of the capacitor are an effective series
resistance of about 5Ω or less and a resonant frequency
above 500kHz. The value of this capacitor may be increased
without limit.
The error comparator has an open-collector output which
requires an external pull-up resistor. Depending on system
requirements, this resistor may be returned to the 5V output
or some other supply voltage. In determining a value for this
resistor, note that while the output is rated to sink 400µA, this
sink current adds to battery drain in a low battery condition.
Suggestedvaluesrangefrom100kto1MΩ. Theresistorisnot
required if this output is unused.
Programming the Output Voltage (LP2951)
At lower values of output current, less output capacitance is
required for output stability. The capacitor can be reduced to
0.33µF for current below 10mA or 0.1µF for currents below
1mA. Using the 8-Pin 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.
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). Alternatively, it may be
programmed for any output voltage between its 1.235V
reference and its 30V maximum rating. An external pair of
resistors is required, as shown in Figure 2.
3
The complete equation for the output voltage is
VOUT = VREF x { 1 + R1/R2 } + IFB R2
The LP2950 will remain stable and in regulation with no load
in addition to the internal voltage divider, unlike many other
voltage regulators. This is especially important in CMOS
RAMkeep-aliveapplications. Whensettingtheoutputvoltage
of the LP2951 version with external resistors, a minimum load
of 1µA is recommended.
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 the 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 = 100kΩ reduces this error to 0.17% while increasing the
resistor program current to 12µA. Since the LP2951 typically
draws60µAatnoloadwithPin2open-circuited, thisisasmall
price to pay.
A 0.1µF capacitor should be placed from the LP2950/LP2951
input to 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 (pin 7)
can cause instability. This may especially be a problem when
using high value external resistors to set the output voltage.
Addinga100pFcapacitorbetweenOutputandFeedbackand
increasing the output capacitor to at least 3.3µF will remedy
this.
Reducing Output Noise
In reference applications it may be 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 method by which noise can be
reduced on the 3 lead LP2950 and is relatively inefficient, as
increasing the capacitor from 1µF to 220µF only decreases
the noise from 430µV to 160µV rms for a 100kHz bandwidth
at 5V output.
Error Detection Comparator Output
Alogiclowoutputwillbeproducedbythecomparatorwhenever
the LP2951 output falls out of regulation by more than
approximately 5%. This figure is the comparator’s built-in
offsetofabout60mVdividedbythe1.235Vreferencevoltage.
(RefertotheblockdiagramonPage1). Thistriplevelremains
“5% below normal” regardless of the programmed output
voltage of the LP2951. 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 can be reduced fourfold by a bypass capacitor across
R1, since it reduces the high frequency gain from 4 to unity.
Pick
1
CBYPASS
2
π
R • 200 Hz
1
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 430µV to 100µV rms 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 output voltages.
Figure 1 is a timing diagram depicting the ERROR signal and
theregulatedoutputvoltageastheLP2951inputisrampedup
and down. The ERROR signal becomes valid (low) at about
1.3V input. It goes high at about 5V input (the input voltage at
February 1999
3-43
LP2950/2951
Micrel
*SEE APPLICATIONS
INFORMATION
+V
8
IN
V
= V
R
R
OUT
REF
4.75V
1
OUTPUT
VOLTAGE
x (1 +
OUT
1.0V
)
100kΩ
2
V
IN
V
5
1
ERROR
ERROR
V
OUT
*
*
OUTPUT
NOT
VALID
NOT
ERROR
LP2951
VALID
3
SHUTDOWN
INPUT
SD
3.3µF
R
1
100
pF
OFF
GND
FB
INPUT
VOLTAGE
5V
ON
4
7
1.23V
1.3V
NOTE: PINS 2 AND 6 ARE LEFT OPEN
* SEE APPLICATIONS INFORMATION
R
V
2
REF
Figure 1. ERROR Output Timing
Figure 2. Adjustable Regulator
Typical Applications
+V
IN
+V
IN
C-MOS
GATE
*SLEEP
INPUT
8
+V
IN
470 kΩ
47kΩ
8
ERROR
5
*V
OUT
≈V
1
IN
V
OUT
ERROR
+V
IN
OUTPUT
+V
OUT
1
LP2951
5
V
OUT
ERROR
ERROR
OUTPUT
SHUTDOWN 3
INPUT
200kΩ
1%
SO
LP2951
3
+
2N3906
SHUTDOWN
INPUT
SD
3.3µF
GND
FB
100kΩ
100pF
OFF
FB
GND
4
7
ON
7
4
1%
100kΩ
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT. CURRENT LIMIT IS TYPICALLY 160mA.
*HIGH INPUT LOWERS VOUT TO 2.5V
Wide Input Voltage Range Current Limiter
5 V Regulator with 2.5 V Sleep Function
3-44
February 1999
LP2950/2951
Micrel
+V
+V
IN
→
+V = 2 30V
1.23
R
I
↓
L
LOAD
I =
L
IN
*V
= 5V
OUT
V
OUT
8
V
IN
LP2950Z
GND
1
+
V
OUT
1µF
LP2951
SHUTDOWN 3
0.1µF
SD
INPUT
GND
FB
4
7
5 Volt Current Limiter
* MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
R
1%
1µF
Low Drift Current Source
3
+V
D
IN
8
1
2
SENSE
+V
IN
MEMORY
V+
D
2
1
5
V
OUT
20
LP2951
#1
1µF
3.6V
NICAD
ERROR
GND
4
27kΩ
EARLY WARNING
RESET
D
D
3
2.7MΩ
4
Q1
8
2
330kΩ
MAIN
OUTPUT
µP
SENSE
+V
IN
1
5
V
V
DO
OUT
LP2951
#2
+
3
SD
ERROR
1µf
GND
4
Regulator with Early Warning and Auxiliary Output
• 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 5 V.
ITS ERROR FLAG BECOMES ACTIVE WHEN VIN ≤ 5.7 V. WHEN VIN DROPS
BELOW 5.3 V, THE ERROR FLAG OF REG. #2 BECOMES ACTIVE AND VIA Q1
LATCHES THE MAIN OUTPUT OFF. WHEN VIN AGAIN EXCEEDS 5.7 V REG. #1
IS BACK IN REGULATION AND THE EARLY WARNING SIGNAL RISES,
UNLATCHING REG. #2 VIA D3.
February 1999
3-45
LP2950/2951
Micrel
+V
IN
8
+5V
4.7mA
20mA
4
8
OUTPUT*
470k
+V
IN
1
V
5
V
2
IN
1
7
OUT
+
5
V
OUT
FB
ERROR
1
7
V
470k
OUT
FB
1N
4001
R
1
LP2951
MIC2951
4
3
1µF
0.1µF
SD
2
RESET
R
GND
4
* HIGH FOR
GND
4
I < 3.5mA
L
360
1N457
MIN. VOLTAGE 4V
Latch Off When Error Flag Occurs
Open Circuit Detector for 4mA to 20mA Current Loop
8
2
+V
SENSE
39kΩ
IN
+V
+
= 5V
1
7
OUT
5
V
OUT
ERROR
LP2951
RESET
1µF
–
C+ 4
3
FB
SD
GND
4
TAP
6
39kΩ
+
100
6V
100kΩ
1%
1%
1%
–
kΩ
LEAD-
ACID
C1
+
<5.8V**
<6.0V**
<6.2V**
BATTERY
1
kΩ
100kΩ
100kΩ
–
C2
+
C1-C4
LP339
1
kΩ
–
C3
+
10kΩ
R
3
1% 20kΩ
*OPTIONAL LATCH OFF WHEN DROP OUT OCCURS. ADJUST R3 FOR C2
SWITCHING WHEN V IS 6.0V
IN
**OUTPUTS GO LOW WHEN V DROPS BELOW DESIGNATED THRESHOLDS.
IN
Regulator with State-of-Charge Indicator
3-46
February 1999
LP2950/2951
Micrel
+
6V
120kΩ
1.5kΩ**
1N457
SEALED
LEAD-
ACID
8
+V
IN
FB
BATTERY
SOURCE
LM385
1
2
MAIN V+
V
OUT
–
LP2951
SENSE
≈ 400kΩ*
FOR 5.5V
MEMORY V+
3
SD
100kΩ
+
20Ω
GND
4
1µF
+
NI-CAD
* Sets disconnect voltage
** Sets disconnect hysteresis
BACKUP
BATTERY
Low Battery Disconnect
For values shown, Regulator shuts down when VIN < 5.5 V and turns on again at 6.0 V. Current drain in disconnected mode is 150µA.
+V
IN
8
10kΩ
+V
IN
5° PRE-SHUTDOWN FLAG
5
1
3
AUX. SHUTDOWN
INPUT
ERROR
MIC2951
SD
3
OFF
V
OUT
ON
EXTERNAL CIRCUIT
PROTECTED FROM
OVER TEMPERATURE
(V+ GOES OFF WHEN
TEMP.> 125°)
GND
4
FB
OR
+
7
TEMP. LM34 OR
RELAY
SENSOR
LM35
8.2kΩ
–
LM34 for 125°F Shutdown
LM35 for 125°C Shutdown
System Over Temperature Protection Circuit
February 1999
3-47
LP2950/2951
Micrel
FEEDBACK
IN
R18
20kΩ
Q15A
Q15B
Q24
R27
Q26
Q25
OUT
Q9
R11
18
kΩ
Q3
Q1
Q4
Q7
SENSE
Q8
Q5
R17
12 kΩ
C1
20
pF
182 kΩ
Q14
R11
20.6
kΩ
Q6
Q17
Q16
5V TAP
R28
60 kΩ
Q2
10
Q20
R1
20 kΩ
Q22
R10
150
kΩ
Q42
R8
31.4 kΩ
Q21
Q23
C2
40 pF
R2
50 kΩ
R15
100 kΩ
R5
180
kΩ
R6
140
kΩ
R9
27.8 kΩ
R12
110
kΩ
R14
350
kΩ
R13
100
kΩ
R16
30 kΩ
Q40
Q13
Q12
R17
Q41
Q11
10 Ω
Q29
R30
30
Q18
Q19
Q28
kΩ
R3
50 kΩ
R4
13 kΩ
R21 8 Ω
50 kΩ
10 kΩ
Q30 Q31
SHDN
R23 60 kΩ
Q37
Q36
R22
150 kΩ
R24
50 kΩ
ERROR
Q38
Q34
R26
60 kΩ
DENOTES CONNECTION ON LP2950 ONLY
R25
2.8 kΩ
GND
Q39
3-48
February 1999
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