MIC2950/2951 Micrel, Inc.
July 2005 1 MIC2950/2951
MIC2950/2951
150mA Low-Dropout Voltage Regulator
Block Diagram
60mV
1.23V
REF.
Error
Amp.
Error Detection
Comparator
182k
60k
1.5µF
SNS
TA
P
E R R
GND
OUT
5V/150mA
Output
TTL/CMOS
Compatible
Error Output
INFB
Unregulated
DC Supply
TTL/CMOS
Control Logic
Input
SHDN
330k
General Description
The MIC2950 and MIC2951 are “bulletproof” micropower volt-
age 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 protec-
tion 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 pin-
compatible 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
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MIC2950/2951 Micrel, Inc.
MIC2950/2951 2 July 2005
Ordering Information
Part Number
Standard Pb-Free** Voltage Accuracy Temp Range* Package
MIC2950-05BZ MIC2950-05YZ 5.0V 0.5% –40°C to +125°C TO-92
MIC2950-06BZ MIC2950-06YZ 5.0V 1.0% –40°C to +125°C TO-92
MIC2951-02BM MIC2951-02YM 5.0V 0.5% –40°C to +125°C 8-pin SOIC
MIC2951-03BM MIC2951-03YM 5.0V 1.0% –40°C to +125°C 8-pin SOIC
MIC2951-02BN Contact Factory 5.0V 0.5% –40°C to +125°C 8-pin Plastic DIP
MIC2951-03BN MIC2951-03YN 5.0V 1.0% –40°C to +125°C 8-pin Plastic DIP
MIC2951-03BMM MIC2951-03YMM 5.0V 1.0% –40°C to +125°C 8-lead MSOP
MIC2951-3.3BM MIC2951-3.3YM 3.3V 1.0% –40°C to +125°C 8-pin SOIC
*Junction temperature
**PB-Free RoHS compliant with “hot-melting solder” exemption
Pin Description
Pin # Pin # Pin Name Pin Function
MIC2950 MIC2951
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 Shutdown/Enable (Input): TTL compatible input. High = shutdown,
low or open = enable.
2 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).
1 8 IN Unregulated Supply Input
Pin Configuration
1
2
3
4
8
7
6
5
IN
FB
TA
P
E R R
OUT
SNS
SHDN
GND
MIC2951-xx
DIP (N), SOIC (M), MM8™ (MM)
(Top View)
3 2 1
OUT
GND
IN
MIC2950-xx
TO-92 (Z)
(Bottom View)
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 coef-
ficient 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.
MIC2950/2951 Micrel, Inc.
July 2005 3 MIC2950/2951
Electrical Characteristics (Note 16)
VIN = 6V; IL = 100µA; CL = 1µF; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; Note 8; unless noted.
Parameter Condition Min Typ Max Units
Output Voltage 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
Output Voltage 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
Output Voltage MIC295x-02/-05 (±0.5%), –40°C to +125°C 4.940 5.060 V
Over Full Temperature Range 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
Output Voltage MIC295x-02/-05 (±0.5%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max) 4.930 5.070 V
Over Load Variation 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
Output Voltage MIC295x-02/-05 (±0.5%), Note 9 20 100 ppm/°C
Temperature Coefficient 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
Line Regulation 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 %
Absolute Maximum Ratings (Note 1)
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
Operating Ratings (Note 2)
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
MIC2950/2951 Micrel, Inc.
MIC2950/2951 4 July 2005
Parameter Condition Min Typ Max Units
Load Regulation 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 %
Dropout Voltage MIC295x-02/-03/-05/-06, IL = 100µA, Note 12 40 80 mV
140 mV
MIC295x-02/-03/-05/-06, IL = 100mA, Note 12 250 300 mV
MIC295x-02/-03/-05/-06, IL = 150mA, Note 12 300 450 mV
600 mV
MIC2951-3.3 (±1%), IL = 100µA, Note 12 40 80 mV
150 mV
MIC2951-3.3 (±1%), IL = 100mA, Note 12 250 350 mV
MIC2951-3.3 (±1%), IL = 150mA, Note 12 320 450 mV
600 mV
MIC2951-4.8 (±1%), IL = 100µA, Note 12 40 80 mV
140 mV
MIC2951-4.8 (±1%), IL = 100mA, Note 12 250 300 mV
MIC2951-4.8 (±1%), IL = 150mA, Note 12 300 450 mV
600 mV
Ground Current MIC295x-02/-03/-05/-06, IL = 100µA 120 180 µA
300 µA
MIC295x-02/-03/-05/-06, IL = 100mA 1.7 2.5 mA
3.5 mA
MIC295x-02/-03/-05/-06, IL = 150mA 4 6 mA
8 mA
MIC2951-3.3 (±1%), IL = 100µA 100 180 µA
300 µA
MIC2951-3.3 (±1%), IL = 100mA 1.7 2.5 mA
MIC2951-3.3 (±1%), IL = 150mA 4 6 mA
10 mA
MIC2951-4.8 (±1%), IL = 100µA 120 180 µA
300 µA
MIC2951-4.8 (±1%), IL = 100mA 1.7 2.5 mA
3.5 mA
MIC2951-4.8 (±1%), IL = 150mA 4 6 mA
8 mA
Dropout Ground Current MIC295x-02/-03/-05/-06 (±0.5%), VIN = 4.5V, IL = 100µA 280 350 µA
400 µA
MIC2951-3.3 (±1%), VIN = 3.0V, IL = 100µA 150 350 µA
400 µA
MIC2951-4.8 (±1%), VIN = 4.3V, IL = 100µA 280 350 µA
400 µA
MIC2950/2951 Micrel, Inc.
July 2005 5 MIC2950/2951
Parameter Condition Min Typ Max Units
Current Limit VOUT = 0V 300 400 mA
450 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, 100 µVRMS
0.01µF bypass Feedback to Output
Reference Voltage MIC295x-02/-05 (±0.5%) 1.220 1.235 1.250 V
1.200 1.260 V
MIC295x-03/-06 (±1%) 1.210 1.235 1.260 V
1.200 1.270 V
MIC2951-3.3 (±1%) 1.210 1.235 1.260 V
1.200 1.270 V
MIC2951-4.8 (±1%) 1.210 1.235 1.260 V
1.200 1.270 V
Reference Voltage 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
Feedback Bias Current 20 40 nA
60 nA
Reference Voltage MIC295x-02/-05 (±0.5%), Note 9 20 ppm/°C
Temperature Coefficient 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
Feedback Bias Current 0.1 nA/°C
Temperature Coefficient
Error Comparator (Flag) VOH = 30V 0.01 1.00 µA
Output Leakage Current 2.00 µA
Error Comparator (Flag) VIN = 4.5V, IOL = 200µA 150 250 mV
Output Low Voltage 400 mV
Error Comparator Note 15 40 60 mV
Upper Threshold Voltage 25 mV
Error Comparator Note 15 75 95 mV
Lower Threshold Voltage 140 mV
Error Comparator Hysteresis Note 15 15 mV
MIC2950/2951 Micrel, Inc.
MIC2950/2951 6 July 2005
Parameter Condition Min Typ Max Units
Shutdown Input Logic Voltage MIC295x-02/-05 (±0.5%) 1.3 V
Low 0.7 V
High 2.0 V
MIC295x-03/-06 (±1%) 1.3 V
Low 0.7 V
High 2.0 V
MIC2951-3.3 (±1%) 1.3 V
Low 0.7 V
High 2.0 V
MIC2951-4.8 (±1%) 1.3 V
Low 0.7 V
High 2.0 V
Shutdown Input Current VSHUTDOWN = 2.4V 30 50 µA
100 µA
VSHUTDOWN = 30V 450 600 µA
750 µA
Regulator Output Current Note 7 3 10 µA
in Shutdown 20 µA
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 diode-
clamped 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 typi-
cally 5% below nominal, 7.5% guaranteed.
Note 16. Specification for packaged product only.
MIC2950/2951 Micrel, Inc.
July 2005 7 MIC2950/2951
Typical Characteristics
Ground Pin Current
Ground Pin CurrentRepresentative UnitsInput Current
Ground Pin CurrentGround Pin CurrentGround Pin Current
Dropout VoltageShort Circuit Current
0.1 1 10 150
10
1
0.1
0.01
0 1 2 3 4 5 6
1
2
3
4
5
6
00
50
100
150
200
250
300
350
400
0 1 2 3 4 5 6 7 8 9 10
120
110
100
90
80
70
60
50
40
30
20
10
0
0 1 2 3 4 5 6 7 8 9 10
5.06
5.04
5.02
5.0
4.98
4.96
4.94
-75 -50 -25 0 25 50 75 100 125 150 0
20
40
60
80
100
120
140
180
0 1 2 3 4 5 6 7 8
350
300
250
200
150
100
50
0
-75 -50 -25 0 25 50 75 100 125 150
7
6
5
4
-75 -50 -25 0 25 50 75 100 125 150
9
7
5
3
00 1 2 3 4 5 6 7 8
450
400
350
300
250
200
150
100
-75 -50 -25 0 25 50 75 100 125 150
600
500
400
300
100
50
0
-75 -50 -25 0 25 50 75 100 125 150
500
400
300
200
100
00.1 110 100
R = 50k
L
R = 33
L
0.2%
I = 100 µA
IN
L
I = 150 mA
IN
L
I = 150 mA
L
I = 100 µA
L
T = 25°C
J
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
TEMPERATURE (°C)INPUT VOLTAGE (V)
TEMPERATURE (°C) INPUT VOLTAGE (V)
TEMPERATURE (°C) OUTPUT CURRENT (mA)
T
N
E
R
R
U
CTNE
C
SE
I
U
Q
)
V
(EGATLO
VT
U
PT
U
O
(TN
ERRUC
TUPN
Iµ)A
)A
m(TN
ERRUC
TUPN
I
)V
(
E
GA
T
L
O
VT
U
P
TUO
(
T
NER
R
U
CT
N
E
CS
E
IUQ µ)A
(
T
NER
R
UC
TN
E
CSE
I
U
Qµ)A
)Am(
T
NER
R
UC
T
NE
CSE
I
U
Q
)Am
(
T
NE
RR
U
C
T
NECS
E
IUQ
)
Am(TN
ERRUC
TIUCR
IC
TROHS
)Vm
(
E
GA
T
LOV
T
U
O
PORD
)
V
m
(
E
GATLOVTUOP
O
RD
R =
L
∞
Ω
Ω
130
140
150
160
L
R = 50 Ω
R = 50k
L
Ω
I = 1 mA
L
I = 0
L
I = 150 mA
L
150
Dropout Characteristics Input Current
INPUT VOLTAGE (V) INPUT VOLTAGE (V)
Output Voltage vs.
Temperature of 3
TEMPERATURE (°C)
Dropout Voltage
TEMPERATURE (°C)
MIC2950/2951 Micrel, Inc.
MIC2950/2951 8 July 2005
Error Comparator Output
Minimum Operating Voltage
Line Transient Response
Load Transient ResponseLoad Transient Response
Ripple RejectionOutput Impedance
2.2
2.0
1.9
1.6 -30
-20
-10
0
10
20
-250
-200
-150
-100
-50
0
50
-2.0 -1.5 -1.0 -0.5 0 0.5 1.0
8
6
4
2
0
-2
0 1 2 3 4 65
2.5
2.0
1.5
1.0
0.5
0.0
0
mV
mV
0 200 400 600 800
125
100
75
50
25
0
-25
-50
0 2 4 6 8 10
80
0 4 8 12 16 20
7
6
5
4
3
2
1
0
-100 0 100 200 300 400 500 600 700
10
5
2
1
0.5
0.2
0.1
0.05
10 100 1K 10K 100K 1M
90
80
70
60
50
40
20
10 10
70
60
50
40
30
20
T = 125°C
A
C = 4.7µ
V = 5V
L
OUT
V = 5V
L
I = 0
L
I = 100 µA
L
TEMPERATURE (°C) FEEDBACK VOLTAGE (V)
TIME (µS)OUTPUT LOW VOLTAGE (V)INPUT VOLTAGE (V)
TIME (mS)
FREQUENCY (Hz)
)V(
E
GATLO
V
GNITARE
P
OM
UM
INIM
)An
(
T
N
ERRUCSAIB
(TNE
RR
UCKCABDEE
Fµ)A
)
V(TUPTUOROT
A
R
A
PMOC
)A
m
(TNE
R
RUCKNI
S
)V
m
(
E
GNAHC
)SMHO(E
C
NADEPMITUPTUO
)
Bd
(
NO
ITC
E
JER
EL
PPIR
)Bd
(
N
OI
T
CE
J
ER
ELP
PIR
Feedback Bias Current Feedback Pin Current
Comparator Sink Current
Enable Transient
Ripple Rejection
2.1
1.8
1.7
-75 -50 -25 0 25 50 75 100 125 150 -75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
OPEN LOOP)
T = 25°C
A
V = 5V
OUT T = 125°C
A
T = 25°C
A
T = -55°C
A
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
mV
8V
6V
4V
mA
µA
CURRENT
C = 4.7µ
V = 5V
L
OUT
L
60
40
20
0
-20
-40
-60
mA
µA
)
V
m
(
E
G
NA
H
CT
NE
RRU
C
C = 15 µ
V = 5V
L
OUT
EGNAHCVOLTAGE
)
V(
EG
A
TL
O
V
)V(EGATLOVNIP
2
0
-2
C = 10 µF
L
IN
OUT
0.02
0.01
I = 100 µA
0
I = 1 mA
0
I = 100 mA
0
C = 4.7µF
L
OUT
30
1010
1010
1 3 4 6
C = 1.5µ
V = 5V
L
IN
OUT
C = 1.5µ
V = 5V
L
IN
OUT
I = 10 mA
L
I = 1 mA
L
80
90
HYSTERESIS
SEPARATE 5V SUPPLY
210 10
FREQUENCY (Hz)
10101010
1 2 3 4 5 6
T = –55°C
A
C = 1.5 µF
L
MIC2951 MIC2951 MIC2951
INPUT OUTPUT VOLTAGE
400
200
-50
MIC2951
MIC2951
MIC2951
TIME (mS)
LOAD OUTPUT VOLTAGE
100
100
LOAD OUTPUT VOLTAGE
100
100
TIME (mS)
SHUTDOWN OUTPUT
FREQUENCY (Hz)
MIC2950/2951 Micrel, Inc.
July 2005 9 MIC2950/2951
120
100
80
60
40
20
0
130
140
150
0
Ripple Rejection
Shutdown Threshold Voltage
80
70
60
50
40
30
20
10
10 10 10101010
1 2 3 4 5 6
0.6
0.8
1.0
1.2
1.4
1.6
1.8
-75 -50 -25 0 25 50 75 100 125 150
FREQUENCY (Hz)
TEMPERATURE (°C)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
30
25
20
0
10
0
-10
400
300
200
100
0
5 10 15 2 0 25 30 0 5 10 15 20 25 30
10 101010
2 3 4 5
-75 -50 -25 0 25 50 75 100 125 150
Output Noise
Line Regulation Rated Output Current
15
10
5
5
-5
FREQUENCY (Hz)
)Bd(NOITCEJE
R
ELPPIR
(
YTISNEDL
AR
TCE
P
Sµ)zH
/
V
)k(ECNATSISER4NIPOT2NIP
)
V
(
EG
ATLO
V
DLOHSE
RHT
N
W
O
DT
U
H
S
INPUT VOLTAGE (V)
)Vm
(EGN
A
HCE
G
AT
L
OVTUPTUO
)Am(TNERRUCTUPTUO
I = 50µA
L
C = 1.5µ
V = 5V
IN
L
OUT
0.01 µ
PIN 7
C = 220µF
I = 100 mA
L
L
C = 4.7µF
L
3.3 µF
L
I = 100 µA
L
I = 1 mA
L
I = 100 µA
L
T = 150°C
J
T = 125°C
J
T = 125°C
JMAX
V = 5V
OUT
T = 25°C
A
T = 50°C
A
T = 85°C
A
TO PC BOARD
I = 100 mA
L
√
Ω
)
A
m(
T
NE
R
R
UCTUPTUO
5
4
2
0
-2
1
-1
0
0 10 20 5030 40
Thermal Response
)
W
(N
O
ITA
P
IS
S
ID )Vm
(
E
G
NA
HC
1.25W
TIME (µS)
JMAX
A
TO PC BOARD
T = 125°C
T = 25°C
T = 85°C
120
100
80
60
40
20
0
130
140
150
0
0 5 10 15 20 3025
Rated Output
INPUT VOLTAGE (V)
0 1 2 53 4
Fold-Back Current Limiting
)Am
(TNE
R
RU
C
TU
P
TUO
OUTPUT VOLTAGE (V)
600
500
400
300
100
200
MIC2951 Divider Resistance
TEMPERATURE (°C)
INPUT VOLTAGE (V)
MIC2951 Maximum
MIC2950 Maximum
POWER OUTPUT VOLTAGE
MIC2950/2951 Micrel, Inc.
MIC2950/2951 10 July 2005
age. (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 overvolt-
age 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, choos-
ing 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 re-
duced 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.
Applications Information
Automotive Applications
The MIC2950/2951 are ideally suited for automotive ap-
plications 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 elec-
trolytics 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 when-
ever 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 volt-
MIC2950/2951 Micrel, Inc.
July 2005 11 MIC2950/2951
MIC2951
IN
OUT
GND F B
E R R O R
5
3
4
1
8
SD
V
V
E R R O R
OUT PUT
SHUTDOWN
INPUT
IN
+V
100kΩ
OUT
V
1.2
30V
1
R100
pF
3.3µF
2
R
1.23V
R E F
V
7
OUT
VR E F
= V
x (1 + )
1
R
2
R
O F F
ON
Noise can be reduced fourfold by a bypass capacitor across
R1, since it reduces the high frequency gain from 4 to unity.
Pick:
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 improve-
ments are more dramatic at higher output voltages.
MIC2951
SD
V
ERROR
GND
47
8
OUT
+V IN
FB
1
5
3
ERROR
OUTPUT
SHUTDOWN
INPUT
47kΩ
*SLEEP
INPUT
100pF
2N3906
200kΩ
1%
100kΩ
C-MOS
GATE
+V IN
1%
100kΩ
+
3.3µF
+V OUT
470 kΩ
OFF
ON
*HIGH INPUT LOWERS VOUT TO 2.5V
Typical Applications
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
Wide Input Voltage Range Current Limiter
5V Regulator with 2.5V Sleep Function
Figure 1. ERROR Output Timing Figure 2. Adjustable Regulator
NOTE: PINS 2 AND 6 ARE LEFT OPEN *SEE APPLICATIONS
INFORMATION
* SEE APPLICATIONS INFORMATION
CBYPASS ≅1
2 R1 • 200 Hz
π
NOT *
VALID
NOT *
VALID
OUTPUT
VOLTAGE
4.75V
ERROR
INPUT
VOLTAGE
5V
1.3V
MIC2950/2951 Micrel, Inc.
MIC2950/2951 12 July 2005
Low Drift Current Source
5-Volt Current Limiter
* MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV,
DEPENDING ON LOAD CURRENT.
870 27
870 29
MIC2950Z
OUT
GND
+VIN *V = 5V
OUT
V
5V BUS
1µF
+
MIC2951
F B
SD
1
3
7
GND
4
VIN
8
OUT
V
SH UTDOWN
INPUT
LOAD
+V = 2 30V
ILIL=1.23V
R
0.1µF
1µF
1%
R
O F F
ON
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, UN-
LATCHING REG. #2 VIA D3.
MIC2951
#1
SENSE
V
ERROR
GND
20
27kΩ
4
5
1
8
OUT
+VIN
2
SENSE
V
ERROR
GND
+
4
5
1
8
OUT
+VIN
2
MEMORY
V+
D2
D1
2.7MΩ
D3
D4
330kΩ
RESET
EARLY WARNING
µP
VDO
SD
3
Q1
1µf
MAIN
OUTPUT
1µF
+VIN
3.6V
NICAD
SENSE
V
ERROR
GND
20
27kΩ
4
5
1
8
OUT
+VIN
2
MIC2951
#2
SENSE
V
ERROR
GND
+
4
5
1
8
OUT
+VIN
2
MEMORY
V+
D2
D1
2.7MΩ
D3
D4
330kΩ
RESET
EARLY WARNING
µP
VDO
SD
3
Q1
1µf
MAIN
OUTPUT
1µF
+VIN
3.6V
NICAD
MIC2950/2951 Micrel, Inc.
July 2005 13 MIC2950/2951
MIC2951
SD
V
E R R O R
GND
4
1
8
OUT
+VIN
F B
6
5
3
TAP
S E N S E
2
+1µF
+V
OUT= 5V
+
–
C1
100kΩ
<5.8V**
+
–
C2
100kΩ
<6.0V**
+
–
C3
100kΩ
<6.2V**
39kΩ
100
kΩ
1%
1
kΩ
1%
1
kΩ
1%
1%
10kΩ
20kΩ
R3
+
–
C4
RESET
39kΩ
6V
LEAD-
ACID
B A T T E R Y
+
C1-C4
LP339
7
Latch Off When Error Flag Occurs
Open Circuit Detector for 4mA to 20mA Current Loop
Regulator with State-of-Charge Indicator
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.
MIC2951
S D
V
ER R OR
GND
4
1
8
OUT
+V IN
F B
5
3
470k
470k
+VIN
RESET
R1
R2
7
VOUT
+
1µF
MIC2951
V
G ND
4
1
8
OUT
VIN
F B
7
0.1µF
1N
4001
4
20mA
OUTPUT*
4.7mA
+5V
15
4
2
MIN. VOLTAGE ≈ 4V
360
1N457
* HIGH FOR
I < 3.5mA
L
MIC2950/2951 Micrel, Inc.
MIC2950/2951 14 July 2005
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.
System Overtemperature Protection Circuit
* Sets disconnect voltage
** Sets disconnect hysteresis
LM34 for 125°F Shutdown
LM35 for 125°C Shutdown
Schematic Diagram
3
MIC2951
SD
V
GND
4
1
8
OUT
+VIN
S E N S E
2
NI-CAD
BA C KU P
B A T T E R Y
20Ω
+
+
1µF
MAIN V+
MEMORY V+
LM385
1.5kΩ**
–
100kΩ
120kΩ
F B
6V
SEALED
LEAD-
ACID
B A T T E R Y
S O U R C E
+
≈ 400kΩ*
FOR 5 .5V
1N457
AUX. SHUTD OW N
INPUT
3
MIC2951
SD
V
GND
4
5
8
OUT
+V
IN
E R R O R
1
7
R E L A Y
EXTERN A L C I R C U I T
PR O T E C T E D F R OM
O V E R T E M P E R A T U R E
(V + G OES O FF WHEN
TEMP.> 125°)
O R
10kΩ
5° P R E-S H U TDOW N FLAG
+VIN
LM34 OR
LM35
TEM P.
S E N S O R
8.2kΩ
–
+
F B
O F F
ON
F E E D B A C K
SENSE
Q15A
OUT
Q24
Q26
R27
182kΩ
5V T A P
R28
60 kΩ
R18
20k Ω
Q25
Q23
Q22
R15
100kΩ
R16
30 k Ω
Q29
Q28
R17
10 Ω
R21 8Ω
R17
12 kΩ
Q31
Q30
R23 60k Ω
SHDN
R24
50 kΩ
R22
150kΩ
Q21
Q19
C2
40 pF
R14
350
k Ω
Q14
R13
100
k Ω
Q18
R12
110
kΩ
Q20
Q9
Q15B
Q8
Q7
R11
20.6
kΩ
Q5
R8
31.4 k Ω
R10
150
k Ω
R9
27.8kΩ
Q11
Q12
Q13
R6
140
kΩ
R5
180
kΩ
R4
13kΩ
R3
50 kΩ
Q2
C1
20
pF
Q4
Q3
R11
18
k Ω
Q6
Q1
10
R1
20 k Ω
R2
50 k Ω
Q41
R30
30
k Ω
Q40
Q34
GN D
Q36
Q37
R25
2.8 k Ω
Q38
E R R O R
R26
60 k Ω
Q39
DEN OT ES CO NN ECT IO N O N M I C2 95 0 O NL Y
Q42
Q16
Q17
50 k Ω
10 k Ω
IN
100 x
MIC2950/2951 Micrel, Inc.
July 2005 15 MIC2950/2951
Package Information
45°
0°–8°
0.228 (5.79)
0.189 (4.8)
PLANE
MAX )
0.010 (0.25)
0.007 (0.18)
0.045 (1.14)
0.0040 (0.102)
0.013 (0.33)
0.150 (3.81)
TYP
PIN 1
INCHES (MM)
0.016 (0.40)
8-Pin SOIC (M)
0.370 (9.40)
0.125 (3.18)
PIN 1
INCH (MM)
0.018 (0.57)
0.100 (2.54)
0.013 (0.330)
0.010 (0.254)
0.300 (7.62)
0.245 (6.22)
0.0375 (0.952)
0.130 (3.30)
8-Pin Plastic DIP (N)
MIC2950/2951 Micrel, Inc.
MIC2950/2951 16 July 2005
0.004 (0.10)
0.035 (0.89)
0.021 (0.53)
0.012 (0.03) R
0.0256 (0.65) TYP
0.012 (0.30) R
5°
0° MIN
0.112 (2.84)
0.116 (2.95)
0.012 (0.03)
0.007 (0.18)
0.005 (0.13)
0.038 (0.97)
0.032 (0.81)
INCH (MM)
0.187 (4.74)
8-Lead MSOP (MM)
3
2
1
10° typ.
5° typ.
5° typ.
0.185 (4.699)
0.175 (4.445)
0.185 (4.699)
0.175 (4.445)
0.085 (2.159) Diam.
0.500 (12.70) Min.
0.090 (2.286) typ.
0.0155 (0.3937)
0.0145 (0.3683)
Seating Plane
0.025 (0.635) Max
Uncontrolled
Lead Diameter
0.016 (0.406)
0.014 (0.356)
0.105 (2.667)
0.095 (2.413)
0.055 (1.397)
0.045 (1.143)
0.090 (2.286) Radius, typ.
0.145 (3.683)
0.135 (3.429)
0.055 (1.397)
0.045 (1.143)
BOTTOM VIEW
TO-92 (Z)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 1999 Micrel, Inc.