MIC2950/2951
Micrel
MIC2950/2951
150mA Low-Dropout Voltage Regulator
General Description
The MIC2950 and MIC2951 are “bulletproof” micropower
voltage regulators with very low dropout voltage (typically
40mV at light loads and 250mV at 100mA), and very low
quiescent current. Like their predecessors, the LP2950 and
LP2951, the quiescent current of the MIC2950/MIC2951
increases only slightly in dropout, thus prolonging battery life.
The MIC2950/MIC2951 are pin for pin compatible with the
LP2950/LP2951, but offer lower dropout, lower quiescent
current, reverse battery, and automotive load dump protection.
The key additional features and protection offered include
higher output current (150mA), positive transient protection
for up to 60V (load dump), and the ability to survive an
unregulated input voltage transient of –20V below ground
(reverse battery).
The plastic DIP and SOIC versions offer additional system
functions such as programmable output voltage and logic
controlled shutdown. The 3-pin TO-92 MIC2950 is pincompatible with the older 5V regulators.
These system functions also include an error flag output that
warns of a low output voltage, which is often due to failing
batteries on the input. This may also be used as a power-on
reset. A logic-compatible shutdown input is also available
which enables the regulator to be switched on and off. This
part may also be pin-strapped for a 5 V output, or programmed
from 1.24 V to 29 V with the use of two external resistors.
Features
•
•
•
•
•
•
•
•
•
•
•
•
High accuracy 3.3, 4.85, or 5V, guaranteed 150mA 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 1.5µF for stability
Current and thermal limiting
Unregulated DC input can withstand –20V reverse battery
and +60V positive transients
Error flag warns of output dropout (MIC2951)
Logic-controlled electronic shutdown (MIC2951)
Output programmable from 1.24V to 29V (MIC2951)
Applications
•
•
•
•
•
•
•
Automotive Electronics
Battery Powered Equipment
Cellular Telephones
SMPS Post-Regulator
Voltage Reference
Avionics
High Efficiency Linear Power Supplies
Block Diagram
Unregulated
DC Supply
FB
IN
OUT
SNS
Error
Amp.
182k
SHDN
TTL/CMOS
Control Logic
Input
60mV
60k
Error Detection
Comparator
TAP
330k
TTL/CMOS
Compatible
Error Output
ERR
1.5µF
1.23V
REF.
GND
MIC2951-0x
February 1999
5V/150mA
Output
3-49
3
MIC2950/2951
Micrel
The MIC2950 is available as either an -05 or -06 version. The
-05 and -06 versions are guaranteed for junction temperatures
from –40°C to +125°C; the -05 version has a tighter output and
reference voltage specification range over temperature. The
MIC2951 is available as an -02 or -03 version.
The MIC2950 and MIC2951 have a tight initial tolerance
(0.5% typical), a very low output voltage temperature coefficient
which allows use as a low-power voltage reference, and
extremely good load and line regulation (0.04% typical). This
greatly reduces the error in the overall circuit, and is the result
of careful design techniques and process control.
Ordering Information
Part Number
Voltage
Accuracy Temperature Range*
Package
MIC2950-05BZ
5.0V
0.5%
–40°C to +125°C
TO-92
MIC2950-06BZ
5.0V
1.0%
–40°C to +125°C
TO-92
MIC2951-02BM
5.0V
0.5%
–40°C to +125°C
8-pin SOIC
MIC2951-03BM
5.0V
1.0%
–40°C to +125°C
8-pin SOIC
MIC2951-02BN
5.0V
0.5%
–40°C to +125°C
8-pin plastic DIP
MIC2951-03BN
5.0V
1.0%
–40°C to +125°C
8-pin plastic DIP
MIC2951-03BMM
5.0V
1.0%
–40°C to +125°C
8-lead MM8™
MIC2951-3.3BM
3.3V
1.0%
–40°C to +125°C
8-pin SOIC
MIC2951-4.8BM
4.85V
1.0%
–40°C to +125°C
8-pin SOIC
* junction temperature
Pin Configuration
MIC2951-xx
MIC2950-xx
3
2
1
OUT
IN
OUT 1
8
IN
SNS 2
7
FB
SHDN 3
6
TAP
GND 4
5
ERR
GND
TO-92 (Z)
(Bottom View)
DIP (N), SOIC (M), MM8™ (MM)
(Top View)
Pin Description
Pin #
MIC2950
Pin #
MIC2951
Pin Name
3
1
OUT
Regulated Output
2
SNS
Sense (Input): Output-voltage sensing end of internal voltage divider for
fixed 5V operation. Not used in adjustable configuration.
3
SHDN
4
GND
Ground
5
ERR
Error Flag (Output): Active low, open-collector output (low = error,
floating = normal).
6
TAP
3.3V/4.85/5V Tap: Output of internal voltage divider when the regulator is
configured for fixed operation. Not used in adjustable configuration.
7
FB
Feedback (Input): 1.235V feedback from internal voltage divider’s TAP (for
fixed operation) or external resistor network (adjustable configuration).
8
IN
Unregulated Supply Input
2
1
Pin Function
Shutdown/Enable (Input): TTL compatible input. High = shutdown,
low or open = enable.
3-50
February 1999
MIC2950/2951
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Input Suppy Voltage (VIN) Note 5 ................. –20V to +60V
Feedback Input Voltage (VFB) Note 6, 7 ...... –1.5V to +26V
Shutdown Input Voltage (VSHDN) Note 6 ..... –0.3V to +30V
Power Dissipation (PD) Note 4 ................ Internally Limited
Storage Temperature .............................. –65°C to + 150°C
Lead Temperature (soldering, 5 sec.) ....................... 260°C
ESD, Note 3
Input Supply Voltage (VIN) ........................... +2.0V to +30V
Junction Temperature (TJ) ....................................... Note 4
MIC2950-05/MIC2950-06 ..................... –40°C to +125°C
MIC2951-02/MIC2950-03 ..................... –40°C to +125°C
Electrical Characteristics
VIN = 6V; IL = 100µA; CL = 1µF; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; Note 8; unless noted.
Parameter
Condition
Output Voltage
Output Voltage
Output Voltage
Over Full Temperature Range
Output Voltage
Over Load Variation
Output Voltage
Temperature Coefficient
Line Regulation
February 1999
Min
Typ
Max
Units
MIC295x-02/-05 (±0.5%), TJ = 25°C
4.975
5.000
5.025
V
MIC295x-03/-06 (±1%), TJ = 25°C
4.950
5.000
5.050
V
MIC2951-3.3 (±1%), TJ = 25°C
3.267
3.300
3.333
V
MIC2951-4.8 (±1%), TJ = 25°C
4.802
4.850
4.899
V
MIC295x-02/-05 (±0.5%), –25°C ≤ TJ ≤ +85°C
4.950
5.050
V
MIC295x-03/-06 (±1%), –25°C ≤ TJ ≤ +85°C
4.925
5.075
V
MIC2951-3.3 (±1%), –25°C ≤ TJ ≤ +85°C
3.251
3.350
V
MIC2951-4.8 (±1%), –25°C ≤ TJ ≤ +85°C
4.777
4.872
V
MIC295x-02/-05 (±0.5%), –40°C to +125°C
4.940
5.060
V
MIC295x-03/-06 (±1%), –40°C to +125°C
4.900
5.100
V
MIC2951-3.3 (±1%), –40°C to +125°C
3.234
3.366
V
MIC2951-4.8 (±1%), –40°C to +125°C
4.753
4.947
V
MIC295x-02/-05 (±0.5%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max)
4.930
5.070
V
MIC295x-03/-06 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max)
4.880
5.120
V
MIC2951-3.3 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max)
3.221
3.379
V
MIC2951-4.8 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max)
4.733
4.967
V
MIC295x-02/-05 (±0.5%), Note 9
20
100
ppm/°C
MIC295x-03/-06 (±1%), Note 9
50
150
ppm/°C
MIC2951-3.3 (±1%), Note 9
50
150
ppm/°C
MIC2951-4.8 (±1%), Note 9
50
150
ppm/°C
MIC295x-02/-05 (±0.5%), Note 10, 11
0.03
0.10
0.20
%
%
MIC295x-03/-06 (±1%), Note 10, 11
0.04
0.20
0.40
%
%
MIC2951-3.3 (±1%), Note 10, 11
0.04
0.20
0.40
%
%
MIC2951-4.8 (±1%), Note 10, 11
0.04
0.20
0.40
%
%
3-51
3
MIC2950/2951
Micrel
Parameter
Condition
Load Regulation
Dropout Voltage
Ground Current
Dropout Ground Current
Min
Typ
Max
Units
MIC295x-02/-05 (±0.5%), 100µA ≤ IL ≤ 150mA, Note 10
0.04
0.10
0.20
%
%
MIC295x-03/-06 (±1%), 100µA ≤ IL ≤ 150mA, Note 10
0.10
0.20
0.30
%
%
MIC2951-3.3 (±1%), 100µA ≤ IL ≤ 150mA, Note 10
0.10
0.20
0.30
%
%
MIC2951-4.8 (±1%), 100µA ≤ IL ≤ 150mA, Note 10
0.10
0.20
0.30
%
%
MIC295x-02/-03/-05/-06, IL = 100µA, Note 12
40
80
140
mV
mV
MIC295x-02/-03/-05/-06, IL = 100mA, Note 12
250
300
mV
MIC295x-02/-03/-05/-06, IL = 150mA, Note 12
300
450
600
mV
mV
MIC2951-3.3 (±1%), IL = 100µA, Note 12
40
80
150
mV
mV
MIC2951-3.3 (±1%), IL = 100mA, Note 12
250
350
mV
MIC2951-3.3 (±1%), IL = 150mA, Note 12
320
450
600
mV
mV
MIC2951-4.8 (±1%), IL = 100µA, Note 12
40
80
140
mV
mV
MIC2951-4.8 (±1%), IL = 100mA, Note 12
250
300
mV
MIC2951-4.8 (±1%), IL = 150mA, Note 12
300
450
600
mV
mV
MIC295x-02/-03/-05/-06, IL = 100µA
120
180
300
µA
µA
MIC295x-02/-03/-05/-06, IL = 100mA
1.7
2.5
3.5
mA
mA
MIC295x-02/-03/-05/-06, IL = 150mA
4
6
8
mA
mA
MIC2951-3.3 (±1%), IL = 100µA
100
180
300
µA
µA
MIC2951-3.3 (±1%), IL = 100mA
1.7
2.5
mA
MIC2951-3.3 (±1%), IL = 150mA
4
6
10
mA
mA
MIC2951-4.8 (±1%), IL = 100µA
120
180
300
µA
µA
MIC2951-4.8 (±1%), IL = 100mA
1.7
2.5
3.5
mA
mA
MIC2951-4.8 (±1%), IL = 150mA
4
6
8
mA
mA
MIC295x-02/-03/-05/-06 (±0.5%), VIN = 4.5V, IL = 100µA
280
350
400
µA
µA
MIC2951-3.3 (±1%), VIN = 3.0V, IL = 100µA
150
350
400
µA
µA
MIC2951-4.8 (±1%), VIN = 4.3V, IL = 100µA
280
350
400
µA
µA
3-52
February 1999
MIC2950/2951
Micrel
Parameter
Condition
Current Limit
Typ
Max
Units
VOUT = 0V
300
400
450
mA
mA
Thermal Regulation
Note 13
0.05
0.20
%/W
Output Noise
10Hz to 100kHz, CL = 1.5µF
430
µVRMS
10Hz to 100kHz, CL = 200µF
160
µVRMS
10Hz to 100kHz, CL = 3.3µF,
0.01µF bypass Feedback to Output
100
µVRMS
Reference Voltage
Reference Voltage
Min
MIC295x-02/-05 (±0.5%)
1.220
1.200
1.235
1.250
1.260
V
V
MIC295x-03/-06 (±1%)
1.210
1.200
1.235
1.260
1.270
V
V
MIC2951-3.3 (±1%)
1.210
1.200
1.235
1.260
1.270
V
V
MIC2951-4.8 (±1%)
1.210
1.200
1.235
1.260
1.270
V
V
MIC295x-02/-05 (±0.5%), Note 14
1.190
1.270
V
MIC295x-03/-06 (±1%), Note 14
1.185
1.285
V
MIC2951-3.3 (±1%), Note 14
1.185
1.285
V
MIC2951-4.8 (±1%), Note 14
1.185
1.285
V
40
60
nA
nA
Feedback Bias Current
Reference Voltage
Temperature Coefficient
20
MIC295x-02/-05 (±0.5%), Note 9
20
ppm/°C
MIC295x-03/-06 (±1%), Note 9
50
ppm/°C
MIC2951-3.3 (±1%), Note 9
50
ppm/°C
MIC2951-4.8 (±1%), Note 9
50
ppm/°C
0.1
nA/°C
Feedback Bias Current
Temperature Coefficient
Error Comparator (Flag)
Output Leakage Current
VOH = 30V
0.01
1.00
2.00
µA
µA
Error Comparator (Flag)
Output Low Voltage
VIN = 4.5V, IOL = 200µA
150
250
400
mV
mV
Error Comparator
Upper Threshold Voltage
Note 15
Error Comparator
Lower Threshold Voltage
Note 15
75
Error Comparator Hysteresis
Note 15
15
February 1999
40
25
3-53
60
mV
mV
95
140
mV
mV
mV
3
MIC2950/2951
Micrel
Parameter
Condition
Shutdown Input Logic Voltage
MIC295x-02/-05 (±0.5%)
Low
High
Min
Units
0.7
V
V
V
0.7
V
V
V
0.7
V
V
V
0.7
V
V
V
2.0
1.3
2.0
MIC2951-3.3 (±1%)
Low
High
1.3
2.0
MIC2951-4.8 (±1%)
Low
High
Regulator Output Current
in Shutdown
Max
1.3
MIC295x-03/-06 (±1%)
Low
High
Shutdown Input Current
Typ
1.3
2.0
VSHUTDOWN = 2.4V
30
50
100
µA
µA
VSHUTDOWN = 30V
450
600
750
µA
µA
3
10
20
µA
µA
Note 7
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions are recommended.
Note 4.
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. Junction-to-ambient thermal resistance for the MM8™ (MM) is 250°C/W.
Note 5.
The maximum positive supply voltage of 60V must be of limited duration (≤100ms) and duty cycle (≤1%). The maximum continuous supply
voltage is 30V.
Note 6.
When used in dual-supply systems where the output terminal sees loads returned to a negative supply, the output voltage should be diodeclamped to ground.
Note 7.
VSHDN ≥ 2V, VIN ≤ 30 V, VOUT = 0, with the FB pin connected to TAP.
Note 8.
Additional conditions for 8-pin devices are VFB = 5V, TAP and OUT connected to SNS (VOUT = 5V) and VSHDN ≤ 0.8V.
Note 9.
Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 10. 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 11. Line regulation for the MIC2951 is tested at 150°C for IL = 1mA. For IL = 100µA 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 12. 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 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 = 10ms.
Note 14. VREF ≤ VOUT ≤ (VIN – 1 V), 2.3V ≤ VIN ≤ 30V, 100µA < IL ≤ 150mA, TJ ≤ TJMAX.
Note 15. Comparator thresholds are expressed in terms of a voltage differential at the FB 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 = 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
95mV x 5V/1.235V = 384mV. 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.
3-54
February 1999
MIC2950/2951
Micrel
Typical Characteristics
Ground Pin Current
Dropout Characteristics
0.1
0.01
0.1
5
4
1
0
1
10
150
1
2
3
4
5
5
6 7
50
150
100
50
5.0
4.98
0.2%
4.96
6
VIN = 6V
IL = 150 mA
5
4
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
Short Circuit Current
200
150
100
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
60
40
20
1
2
3
4
5
6
7
8
INPUT VOLTAGE (V)
Ground Pin Current
9
7
5
IL = 150 mA
3
0
0
1
2
3
4
5
6
7
8
INPUT VOLTAGE (V)
Dropout Voltage
500
IL = 150 mA
500
400
300
100
IL = 100 µA
50
0
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
3-55
DROPOUT VOLTAGE (mV)
250
3
IL = 0
80
Dropout Voltage
DROPOUT VOLTAGE (mV)
300
100
0
600
350
IL = 1 mA
120
0
7
0
-75 -50 -25 0 25 50 75 100 125 150
400
140
Ground Pin Current
450
5 6 7 8 9 10
Ground Pin Current
TEMPERATURE (°C)
QUIESCENT CURRENT (mA)
VIN = 6V
IL = 100 µA
200
February 1999
100
INPUT VOLTAGE (V)
QUIESCENT CURRENT (µA)
5.02
Ground Pin Current
300
RL = ∞
150
180
5.04
INPUT VOLTAGE (V)
250
200
0 1 2 3 4
4.94
-75 -50 -25 0 25 50 75 100 125 150
8 9 10
350
R L = 50k Ω
250
INPUT VOLTAGE (V)
QUIESCENT CURRENT (mA)
2 3 4
300
6
5.06
0 1
350
Output Voltage vs.
Temperature of 3
Representative Units
R L = 50Ω
Input Current
0
0
OUTPUT VOLTAGE (V)
INPUT CURRENT (mA)
R L = 33 Ω
2
Input Current
QUIESCENT CURRENT (µA)
R L = 50kΩ
3
LOAD CURRENT (mA)
SHORT CIRCUIT CURRENT (mA)
INPUT CURRENT (µA)
1
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
400
6
OUTPUT VOLTAGE (V)
QUIESCENT CURRENT
10
400
300
200
TJ = 25 °C
100
0
150
0.1
1
10
100
OUTPUT CURRENT (mA)
MIC2951
Minimum Operating Voltage
20
2.0
1.9
1.8
1.7
1.6
-75 -50 -25 0 25 50 75 100 125 150
10
0
-10
-20
-30
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4
HYSTERESIS
2
0
PULLUP RESISTOR TO
SEPARATE 5V SUPPLY
1
2
3
4
5
1.5
1.0
TA = -55°C
0.5
4
6
8
10
OUTPUT VOLTAGE
CHANGE (mV)
2
80
60
40
20
0
-20
-40
-60
LOAD
CURRENT
0
TA = 25°C
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
6
C L = 4.7 µF
VOUT = 5V
100
mA
100
µA
TA = 125°C
2.0
Load Transient Response
125
100
75
50
25
0
-25
-50
100
mA
100
µA
I0 = 100 mA
0.5
VOUT = 5V
C L = 4.7 µF
0.05
0.02
0.01
10
100
1K
10K 100K 1M
FREQUENCY (Hz)
-150
TA = 25°C
-200
TA = –55°C
-250
-2.0 -1.5 -1.0 -0.5 0
-50
mV
C L = 4.7µF
IL = 1 mA
VOUT = 5V
8V
6V
4V
200
C L = 15 µF
VOUT = 5V
12
16
20
7
6
5
4
3
2
1
0
2
0
-2
IL = 10 mA
VIN = 8V
CL = 10 µF VOUT = 5V
-100 0 100 200 300 400 500 600 700
Ripple Rejection
90
70
IL = 0
60
50
20
800
TIME (µS)
80
40
600
CL = 1.5 µF
Ripple Rejection
30
400
MIC2951
Enable Transient
8
1.0
0
Load Transient Response
4
0.5
Line Transient Response
400
mV
200
mV
TIME (mS)
RIPPLE REJECTION (dB)
OUTPUT IMPEDANCE (OHMS)
I0 = 1 mA
0.2
0.1
-100
0
90
I0 = 100 µA
2
1
TA = 125°C
TIME (µS)
0
Output Impedance
5
-50
OUTPUT LOW VOLTAGE (V)
TIME (mS)
10
OUTPUT VOLTAGE
CHANGE
VOUT = 5V
INPUT VOLTAGE (V)
OUTPUT VOLTAGE
LOAD
CHANGE (mV)
CURRENT
MIC2951
Comparator Sink Current
INPUT
VOLTAGE
2.5
6
0
PIN 7 DRIVEN BY EXTERNAL
SOURCE (REGULATOR RUN
OPEN LOOP)
0
FEEDBACK VOLTAGE (V)
SHUTDOWN
OUTPUT
PIN VOLTAGE (V) VOLTAGE (V)
MIC2951
Error Comparator Output
-2
MIC2951
Feedback Pin Current
TEMPERATURE (°C)
SINK CURRENT (mA)
COMPARATOR OUTPUT (V)
8
50
FEEDBACK CURRENT (µA)
2.1
MIC2951
Feedback Bias Current
RIPPLE REJECTION (dB)
2.2
Micrel
BIAS CURRENT (nA)
MINIMUM OPERATING VOLTAGE (V)
MIC2950/2951
CL = 1.5 µF
VIN = 6V
VOUT = 5V
101
10 2
10 3
IL = 100 µA
10 4
10
FREQUENCY (Hz)
3-56
106
80
CL = 1.5 µF
VIN = 6V
VOUT = 5V
70 I = 1 mA
L
60
50
40
30
20
101
IL = 10 mA
102
10 3
10 4
10 5
106
FREQUENCY (Hz)
February 1999
Ripple Rejection
VOLTAGE NOISE
SPECTRAL DENSITY (µV/√ Hz)
IL = 50 µA
60
IL = 100 mA
50
40
CL = 1.5 µF
30 VIN = 6V
VOUT = 5V
20
10
101
102
10 3
10 4
10 5
Output Noise
IL = 100 mA
3.0
CL = 4.7 µF
2.5
CL = 220 µF
2.0
CL =
3.3 µF
1.5
1.0
0.01 µF
BYPASS
PIN 1 TO
PIN 7
0.5
0.0
102
106
1.8
1.6
1.4
1.2
1.0
0.8
0.6
-75 -50 -25 0 25 50 75 100 125 150
OUTPUT VOLTAGE CHANGE (mV)
SHUTDOWN THRESHOLD VOLTAGE (V)
Shutdown Threshold Voltage
TJ
100
80
MAX
= 125°C
TA = 25°C
60
40
T = 85°C
20
A
0
0
5
10
15
20
25
INPUT VOLTAGE (V)
February 1999
30
POWER
OUTPUT VOLTAGE
DISSIPATION (W) CHANGE (mV)
OUTPUT CURRENT (mA)
TO-92 PACKAGE
.25" LEADS SOLDERED
TO PC BOARD
120
200
100
0
-75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
MIC2951 Maximum
Rated Output Current
30
25
20
15
T = 150°C
10 J
5
0
10
5 TJ = 125°C
0
-5
-10
5
10
15
150
IL = 100 µA
IL = 1 mA
IL = 100 µA
8-PIN SOIC
SOLDERED
TO PC BOARD
140
TJ
130
= 125°C
VOUT = 5V
TA = 25°C
100
80
60 TA = 50°C
40
TA = 85°C
20
0
20
25
30
0
Thermal Response
600
5
4
2
0
-2
1
MAX
120
INPUT VOLTAGE (V)
MIC2950 Maximum
Rated Output
130
10 5
300
Line Regulation
TEMPERATURE (°C)
140
10 4
MIC2951 Divider Resistance
400
FREQUENCY (Hz)
FREQUENCY (Hz)
150
10 3
OUTPUT CURRENT (mA)
70
3.5
OUTPUT CURRENT (mA)
RIPPLE REJECTION (dB)
80
Micrel
PIN 2 TO PIN 4 RESISTANCE (kΩ )
MIC2950/2951
1.25W
5
10 15 20 25
INPUT VOLTAGE (V)
30
Fold-Back Current Limiting
500
400
300
200
0
-1
100
0
10
20
30
TIME (µS)
3-57
40
50
0
1
2
3
4
OUTPUT VOLTAGE (V)
5
3
MIC2950/2951
Micrel
Applications Information
Automotive Applications
The MIC2950/2951 are ideally suited for automotive
applications for a variety of reasons. They will operate over a
wide range of input voltages, have very low dropout voltages
(40mV at light loads), and very low quiescent currents. These
features are necessary for use in battery powered systems,
such as automobiles. They are also “bulletproof” devices; with
the ability to survive both reverse battery (negative transients
up to 20V below ground), and load dump (positive transients
up to 60V) conditions. A wide operating temperature range
with low temperature coefficients is yet another reason to use
these versatile regulators in automotive designs.
External Capacitors
A 1.5 µF (or greater) capacitor is required between the
MIC2950/MIC2951 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 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 effective
series resistance of about 5Ω or less and a resonant frequency
above 500kHz. The value of this capacitor may be increased
without limit.
At lower values of output current, less output capacitance is
required for output stability. The capacitor can be reduced to
0.5µF for current below 10mA or 0.15µF for currents below 1
mA. 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 150mA load at
1.23V output (Output shorted to Feedback) a 5µF (or greater)
capacitor should be used.
The MIC2950 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 RAM
keep-alive applications. When setting the output voltage of
the MIC2951 version with external resistors, a minimum load
of 1µA is recommended.
A 0.1µF capacitor should be placed from the MIC2950/
MIC2951 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 MIC2951 Feedback terminal (pin 7)
can cause instability. This may especially be a problem when
using high value external resistors to set the output voltage.
Adding a 100pF capacitor between Output and Feedback and
increasing the output capacitor to at least 3.3µF will remedy
this.
Error Detection Comparator Output
A logic low output will be produced by the comparator whenever
the MIC2951 output falls out of regulation by more than
approximately 5%. This figure is the comparator’s built-in
offset of about 60mV divided by the 1.235V reference voltage.
(Refer to the block diagram on Page 1). This trip level remains
“5% below normal” regardless of the programmed output
voltage of the MIC2951. 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, thermal limiting, or overvoltage on
input (over ≅ 40V).
Figure 1 is a timing diagram depicting the ERROR signal and
the regulated output voltage as the MIC2951 input is ramped
up and down. 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—for 5.0V applications). Since
the MIC2951’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 does not vary with load.
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 output or
some other supply voltage. In determining a value for this
resistor, note that while the output is rated to sink 200µA, 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 (MIC2951)
The MIC2951 may be pin-strapped for 5V (or 3.3V or 4.85V)
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.
The complete equation for the output voltage is
VOUT = VREF x { 1 + R1/R2 } + IFB R1
where VREF is the nominal 1.235 reference voltage and IFB is
the feedback pin bias current, nominally –20nA. The minimum
recommended load current of 1 µA forces an upper limit of
1.2MΩ 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 = 100k reduces this error to 0.17% while
increasing the resistor program current to 12 µA.
Reducing Output Noise
In some 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 MIC2950 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.
3-58
February 1999
MIC2950/2951
Micrel
Noise can be reduced fourfold by a bypass capacitor across
R1, since it reduces the high frequency gain from 4 to unity.
Pick:
1
2 π R1 • 200 Hz
CBYPASS ≅
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.
4.75V
+VIN
OUTPUT
VOLTAGE
ERROR
100kΩ
NOT *
VALID
5 ERROR
ERROR
OUTPUT
NOT
*
VALID
8
VIN
VOUT 1
VOUT = V REF
R1
x (1 +
)
R2
VOUT
1.2 30V
MIC2951
INPUT
VOLTAGE
SHUTDOWN 3
SD
INPUT
5V
3.3µF
R1 100
pF
OFF
1.3V
GND
4
ON
FB
7
1.23V
* SEE APPLICATIONS INFORMATION
*SEE APPLICATIONS
INFORMATION
NOTE: PINS 2 AND 6 ARE LEFT OPEN
Figure 1. ERROR Output Timing
3
R2
V REF
Figure 2. Adjustable Regulator
870 23
Typical Applications
+V IN
*SLEEP
INPUT
47kΩ
ERROR
OUTPUT
+VIN
C-MOS
GATE
5
470 kΩ
8
+V IN
ERROR
8
+VIN
SHUTDOWN 3
SD
INPUT
OFF
GND
ON
4
FB
5 ERROR
SHUTDOWN
INPUT
3
200kΩ
+
2N3906 1%
100kΩ
100pF
*VOUT ≈VIN
VOUT 1
MIC2951
+V OUT
V OUT 1
MIC2951
ERROR
OUTPUT
OFF
3.3µF
ON
SD
GND
4
FB
7
7
1%
100kΩ
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
*HIGH INPUT LOWERS VOUT TO 2.5V
Wide Input Voltage Range Current Limiter
5V Regulator with 2.5V Sleep Function
February 1999
3-59
870 25
MIC2950/2951
Micrel
+V = 2 → 30V
I L↓
5V BUS
1.23V
I L= R
LOAD
+V IN
VOUT
8
VIN
*V
OUT≈5V
MIC2950Z
VOUT 1
+
1µF
MIC2951
SHUTDOWN 3 SD
INPUT
OFF
ON
GND
0.1µF
GND
FB
4
870 27
7
R
1%
5-Volt Current Limiter
1µF
* MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
Low Drift Current Source
+V IN
D1
8
+V IN
2
SENSE
VOUT
D2
1
MEMORY
V+
20
MIC2951
#1
5
ERROR
1µF
3.6V
NICAD
GND
4
27kΩ
870 29
Q1
D3
D4
2.7MΩ
EARLY WARNING
RESET
8
+V IN
2
SENSE
VOUT
1
MIC2951
#2
5
3
SD
ERROR
330kΩ
MAIN
OUTPUT
+
µP
VDO
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.
3-60
February 1999
MIC2950/2951
Micrel
+V IN
8
+V IN
470kΩ
5
470kΩ
8
VOUT 1
ERROR
FB
SD
+
RESET
V OUT
1N
4001
R1
7
1µF
4
7
2
FB
GND
4
360
* HIGH FOR
IL < 3.5mA
1N457
MIN. VOLTAGE
Latch Off When Error Flag Occurs
OUTPUT*
5
1
MIC2951
0.1µF
R2
GND
4
1
V IN
VOUT
MIC2951
3
+5V
4.7mA
20mA
4
4V
Open Circuit Detector for 4mA to 20mA Current Loop
8
+V IN
39kΩ
5
2
SENSE
VOUT 1
ERROR
RESET
MIC2951
–
3
C4
+
GND
4
39kΩ
+
6V
1%
LEADACID
BATTERY
1%
100
kΩ
FB
SD
100kΩ
–
C1
<5.8V**
100kΩ
–
C2
+
C1-C4
LP339
1%
1
kΩ
<6.0V**
100kΩ
–
C3
+
R3
1%
7
TAP
6
+
1
kΩ
3
+V OUT = 5V
+
1µF
<6.2V**
10kΩ
870 33
20kΩ
C1 TO C4 ARE COMPARATORS (LP339 OR EQUIVALENT)
*OPTIONAL LATCH OFF WHEN DROP OUT OCCURS. ADJUST R3 FOR C2
SWITCHING WHEN VIN IS 6.0V
**OUTPUTS GO LOW WHEN VIN DROPS BELOW DESIGNATED THRESHOLDS.
Regulator with State-of-Charge Indicator
February 1999
3-61
MIC2950/2951
Micrel
+
6V
120kΩ
1.5kΩ**
SEALED
1N457
LEADACID
BATTERY FB
LM385
SOURCE
8
+V IN
VOUT 1
–
≈ 400kΩ*
FOR 5.5V
MIC2951
3
100kΩ
SENSE
SD
2
1µF
GND
4
* Sets disconnect voltage
** Sets disconnect hysteresis
+
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.
+VIN
8
+VIN
3
AUX. SHUTDOWN
INPUT
10kΩ
ERROR
SD
5° PRE-SHUTDOWN FLAG
5
MIC2951
OFF
VOUT 1
ON
GND
4
+
EXTERNAL CIRCUIT
PROTECTED FROM
OVER TEMPERATURE
(V+ GOES OFF WHEN
TEMP.> 125°)
FB
7
TEMP. LM34 OR
SENSOR
LM35
–
OR
RELAY
8.2kΩ
LM34 for 125°F Shutdown
LM35 for 125°C Shutdown
System Overtemperature Protection Circuit
Schematic Diagram
FEEDBACK
IN
R18
20kΩ
Q15A
100 x
Q15B
Q24
Q26
Q25
OUT
Q9
Q3
R11
18
kΩ
Q4
Q7
Q6
R11
20.6
kΩ
Q1
10
R2
50 kΩ
Q17
Q16
R27
182 kΩ
R17
12 kΩ
Q14
5V TAP
R28
60 kΩ
Q2
Q20
R1
20 kΩ
Q42
SENSE
Q8
Q5
C1
20
pF
R5
180
kΩ
Q40
R6
140
kΩ
Q13
Q22
R10
150
kΩ
R8
31.4 kΩ
Q21
R9
27.8 kΩ
R12
110
kΩ
Q12
Q41
Q23
C2
40 pF
R13
100
kΩ
R15
100 kΩ
R14
350
kΩ
R16
30 kΩ
Q11
R17
10 Ω
Q29
R30
30
kΩ
Q18
Q19
Q28
R3
50 kΩ
R4
13 kΩ
R21 8 Ω
50 kΩ
Q30 Q31
Q37
10 kΩ
R22
150 kΩ
Q36
SHDN
R24
50 kΩ
R23 60 kΩ
ERROR
Q38
Q34
R26
60 kΩ
DENOTES CONNECTION ON MIC2950 ONLY
R25
2.8 kΩ
GND
Q39
3-62
February 1999