MIC2937A/29371/29372
Micrel, Inc.
MIC2937A/29371/29372
750mA Low-Dropout Voltage Regulator
General Description
The MIC2937A family are “bulletproof” efficient voltage regu-
lators with very low dropout voltage (typically 40mV at light
loads and 300mV at 500mA), and very low quiescent current
(160µA typical). The quiescent current of the MIC2937A in-
creases only slightly in dropout, thus prolonging battery life.
Key MIC2937A features include protection against reversed
battery, fold-back current limiting, and automotive “load dump”
protection (60V positive transient).
The MIC2937 is available in several configurations. The
MIC2937A-xx devices are three pin fixed voltage regulators
with 3.3V, 5V, and 12V outputs available. The MIC29371 is
a fixed regulator offering logic compatible ON/OFF switching
input and an error flag output. This flag may also be used as
a power-on reset signal. A logic-compatible shutdown input
is provided on the adjustable MIC29372, which enables the
regulator to be switched on and off.
Features
•
•
•
•
•
•
•
•
•
•
•
•
High output voltage accuracy
Guaranteed 750mA output
Low quiescent current
Low dropout voltage
Extremely tight load and line regulation
Very low temperature coefficient
Current and thermal limiting
Input can withstand –20V reverse battery and +60V posi-
tive transients
Error flag warns of output dropout
Logic-controlled electronic shutdown
Output programmable from 1.24V to 26V(MIC29372)
Available in TO-220, TO-263, TO-220-5, and TO-263-5
packages.
Battery Powered Equipment
Cellular Telephones
Laptop, Notebook, and Palmtop Computers
PCMCIA V
CC
and V
PP
Regulation/Switching
Bar Code Scanners
Automotive Electronics
SMPS Post-Regulator/ DC to DC Modules
High Efficiency Linear Power Supplies
Applications
•
•
•
•
•
•
•
•
Pin Configuration
INPUT GROUND OUTPUT
TO-263 Package
(MIC2937A-xxBU/WU)
Five Lead Package Pin Functions:
MIC29371 MIC29372
1) Error
Adjust
2) Input
Shutdown
3) Ground
Ground
4) Output
Input
5) Shutdown Output
TO-263-5 Package
(MIC29371/29372BU/WU)
1 2 3
1 2 3 4 5
INPUT GROUND OUTPUT
TO-220 Package
(MIC2937A-xxBT/WT)
1 2 3
1 2 3 4 5
TO-220-5 Package
(MIC29371/29372BT/WT)
The TAB is Ground on the TO-220 and TO-263 packages.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
May 2006
1
MIC2937A/29371/29372
MIC2937A/29371/29372
Micrel, Inc.
Ordering Information
Part Number
Standard
MIC2937A-3.3BU
MIC2937A-3.3BT
MIC2937A-5.0BU
MIC2937A-5.0BT
MIC2937A-12BU
MIC2937A-12BT
MIC29371-3.3BU
MIC29371-3.3BT
MIC29371-5.0BU
MIC29371-5.0BT
MIC29371-12BU
MIC29371-12BT
MIC29372BU
MIC29372BT
RoHS Compliant*
MIC2937A-3.3WU
MIC2937A-3.3WT
MIC2937A-5.0WU
MIC2937A-5.0WT
MIC2937A-12WU
MIC2937A-12WT
MIC29371-3.3WU
MIC29371-3.3WT
MIC29371-5.0WU
MIC29371-5.0WT
MIC29371-12WU
MIC29371-12WT
MIC29372WU
MIC29372WT
Voltage
3.3V
3.3V
5.0V
5.0V
12V
12V
3.3V
3.3V
5.0V
5.0V
12V
12V
ADJ
ADJ
Junction Temp. Range
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
–40ºC to +125ºC
Package
TO-263-3
TO-220-3
TO-263-3
TO-220-3
TO-263-3
TO-220-3
TO-263-5
TO-220-5
TO-263-5
TO-220-5
TO-263-5
TO-220-5
TO-263-5
TO-220-5
* RoHS compliant with ‘high-melting solder’ exemption.
MIC2937A/29371/29372
2
May 2006
MIC2937A/29371/29372
Micrel, Inc.
Operating Input Supply Voltage..................................................2V
†
to 26V
Adjust Input Voltage (Notes
9 and 10).................................–1.5V
to +26V
Shutdown Input Voltage .......................................................–0.3V to +30V
Error Comparator Output Voltage.........................................–0.3V to +30V
Across the full operating temperature, the minimum input voltage range for
full output current is 4.3V to 26V. Output will remain in-regulation at lower
output voltages and low current loads down to an input of 2V at 25°C.
†
Absolute Maximum Ratings
Power Dissipation (Note
1)...............................................Internally
Limited
Lead Temperature (Soldering, 5 seconds).........................................260°C
Storage Temperature Range.............................................–65°C to +150°C
Operating Junction Temperature Range ..........................–40°C to +125°C
TO-220
θ
JC
.....................................................................................2.5°C/W
TO-263
θ
JC
.....................................................................................2.5°C/W
Input Supply Voltage..............................................................–20V to +60V
Electrical Characteristics
Limits in standard typeface are for T
J
= 25°C and limits in
boldface
apply over the full operating temperature range. Unless other-
wise specified, V
IN
= V
OUT
+ 1V, I
L
= 5mA, C
L
= 10µF. The MIC29372 are programmed for a 5V output voltage, and V
SHUTDOWN
≤ 0.6V
(MIC29371-xx and MIC29372 only).
Symbol
V
O
Parameter
Output Voltage
Accuracy
Conditions
Variation from factory trimmed V
OUT
5mA ≤ I
L
≤ 500mA
MIC2937A-12 and 29371-12 only:
5mA ≤ I
L
≤ 500mA
(Note
2)
Output voltage > 10V
V
IN
= V
OUT
+ 1V to 26V
I
L
= 5 to 500mA
(Note
3)
I
L
= 5mA
I
L
= 100mA
I
L
= 500mA
I
L
= 750mA
I
GND
Ground Pin Current
(Note
5)
I
L
= 5mA
I
L
= 100mA
I
L
= 500mA
I
L
= 750mA
V
IN
= 0.5V less than designed V
OUT
(V
OUT
≥ 3.3V)
I
O
= 5mA
V
OUT
= 0V
(Note
6)
(Note
7)
C
L
= 10µF
C
L
= 100µF
Min
–1
–2
–2.5
–1.5
–3
–4
Typical
Max
1
2
2.5
1.5
3
4
100
350
0.10
0.40
0.16
0.30
150
180
Units
%
ΔV
O
ΔT
ΔV
O
V
O
ΔV
O
V
O
V
IN
– V
O
Output Voltage
Temperature Coef.
Line Regulation
Load Regulation
Dropout Voltage
(Note
4)
20
80
0.03
0.04
80
200
240
300
420
370
160
1
8
15
200
ppm/°C
%
%
mV
Output voltage > 10V
Output voltage > 10V
I
GNDDO
I
LIMIT
ΔV
O
ΔP
D
e
n
Ground Pin
Current at Dropout
(Note
5)
Current Limit
Thermal Regulation
Output Noise
Voltage
(10Hz to 100kHz)
600
750
250
300
2.5
3
13
16
25
500
µA
mA
µA
1.1
0.05
400
260
1.5
2
0.2
A
%/W
µV RMS
I
L
= 100mA
May 2006
3
MIC2937A/29371/29372
MIC2937A/29371/29372
Micrel, Inc.
Electrical Characteristics
(Continued)
MIC29372
Parameter
Reference Voltage
Reference Voltage
Adjust Pin
Bias Current
Reference Voltage
Temperature
Coefficient
Adjust Pin Bias
Current Temperature
Coefficient
Error Comparator
Output Leakage
Current
Output Low
Voltage
Upper Threshold
Voltage
Lower Threshold
Voltage
Hysteresis
Shutdown Input
Input Logic Voltage
Low (ON)
(Note
7)
(Note
8)
Conditions
Min
1.223
1.210
1.204
20
20
Typical
1.235
Max
1.247
1.260
1.266
40
60
Units
V
V max
V
nA
ppm/°C
0.1
nA/°C
MIC29371
V
OH
= 26V
V
IN
= 4.5V
I
OL
= 250µA
(Note
9)
(Note
9)
(Note
9)
40
25
0.01
150
60
75
15
95
140
1.00
2.00
250
400
µA
mV
mV
mV
mV
MIC29371/MIC29372
1.3
High (OFF)
V
SHUTDOWN
= 2.4V
V
SHUTDOWN
= 26V
2.0
30
0.7
V
Shutdown Pin
Input Current
50
100
600
750
10
20
µA
450
3
µA
µA
Regulator Output
Current in Shutdown
(Note
10)
MIC2937A/29371/29372
4
May 2006
MIC2937A/29371/29372
Micrel, Inc.
Note 1:
Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not
apply when operating the device outside of its rated operating conditions. The maximum allowable power dissipation is a function of the
maximum junction temperature, T
J (MAX)
, the junction-to-ambient thermal resistance,
θ
JA
, and the ambient temperature, T
A
. The maximum
allowable power dissipation at any ambient temperature is calculated using: P
(MAX)
= (T
J(MAX)
– T
A
) /
θ
JA.
Exceeding the maximum allowable
power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
Note 2:
Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 3:
Regulation is measured at constant junction temperature using low duty cycle pulse testing. Changes in output voltage due to
heating effects are covered by the thermal regulation specification.
Note 4:
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 low values of programmed output voltage, the minimum input supply voltage of 4.3V over temperature must
be taken into account. The MIC2937A operates down to 2V of input at reduced output current at 25°C.
Note 5:
Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current
plus the ground pin current.
Note 6:
The MIC2937A family features fold-back current limiting. The short circuit (V
OUT
= 0V) current limit is less than the maximum
current with normal output voltage.
Note 7:
Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, exclud-
ing load or line regulation effects. Specifications are for a 200mA load pulse at V
IN
= 20V (a 4W pulse) for T = 10ms.
Note 8:
V
REF
≤ V
OUT
≤ (V
IN
– 1 V), 4.3V ≤ V
IN
≤ 26V, 5mA < I
L
≤ 750 mA, T
J
≤ T
J MAX.
Note 9:
Comparator thresholds are expressed in terms of a voltage differential at the Adjust terminal below the nominal reference voltage
measured at 6V input (for a 5V regulator). To express these thresholds in terms of output voltage change, multiply by the error amplifier
gain = V
OUT
/V
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 95 mV x 5V/1.235 V = 384 mV. Thresholds remain constant as a percent of V
OUT
as V
OUT
is varied, with the dropout
warning occurring at typically 5% below nominal, 7.7% guaranteed.
Note 10:
Circuit of Figure 3 with R1 ≥ 150kΩ. V
SHUTDOWN
≥ 2V and V
IN
≤ 26V,V
OUT
= 0.
Note 11:
When used in dual supply systems where the regulator load is returned to a negative supply, the output voltage must be diode
clamped to ground.
Note 12:
Maximum positive supply voltage of 60V must be of limited duration (< 100ms) and duty cycle ( ≤ 1%). The maximum continu-
ous supply voltage is 26V.
Schematic Diagram
IN
FEEDBACK
R18
20 kΩ
Q15A
Q15B
Q24
Q25
Q26
OUT
Q9
Q3
R11
18
kΩ
C1
20
pF
Q4
Q5
Q7
SENSE
Q8
Q16
Q6
Q1
10
R11
20.6
kΩ
Q17
Q14
R17
12 kΩ
R27
V TAP
R28
Q2
Q20
Q42
R1
20 kΩ
R8
31.4 k Ω
R10
150
kΩ
Q22
R2
50 kΩ
R5
180
kΩ
Q13
R6
140
kΩ
C2
40 pF
Q21
R15
100 k Ω
R16
30 kΩ
Q23
R9
27.8 k Ω
Q40
Q41
R30
30
kΩ
Q12
Q11
R12
110
kΩ
R13
100
kΩ
R14
350
kΩ
Q18
R3
50 kΩ
Q19
Q29
R17
10Ω
R4
13 kΩ
Q28
R21 8 Ω
50 kΩ
Q37
Q30
Q31
R24
50 kΩ
Q36
10 kΩ
R22
150 k Ω
R23 60 k Ω
SHDN
ERROR
Q38
R26
60 kΩ
Q34
R25
2.8 kΩ
DENOTES CONNECTION ON
MIC2937A-xx AND MIC29371-xx
VERSIONS ONLY
Q39
GND
May 2006
5
MIC2937A/29371/29372
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