MIC2940A/2941A
1.2A Low-Dropout Voltage Regulator
General Description
Features
The MIC2940A and MIC2941A are “bulletproof” efficient
voltage regulators with very low dropout voltage (typically
40mV at light loads and 350mV at 1A), and low quiescent
current (240µA typical). The quiescent current of the
MIC2940A increases only slightly in dropout, thus
prolonging battery life. Key MIC2940A features include
protection against reversed battery, fold-back current
limiting, and automotive “load dump” protection (60V
positive transient).
The MIC2940 is available in both fixed voltage (3.3V, 5V,
and 12V) and adjustable voltage configurations. The
MIC2940A-xx devices are three pin, fixed voltage
regulators. A logic-compatible shutdown input is provided
on the adjustable MIC2941A, which enables the regulator
to be switched on and off.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
•
•
•
•
•
•
•
•
High output voltage accuracy
Guaranteed 1.25A 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
positive transients
• Logic-controlled electronic shutdown
• Output programmable from 1.24V to 26V(MIC2941A)
• Available in TO-220, TO-263, TO-220-5, and TO-263-5
packages.
Applications
• Battery powered equipment
• Cellular telephones
• Laptop, notebook, and palmtop computers
• PCMCIA VCC and VPP regulation/switching
• Bar code scanners
• Automotive electronics
• SMPS post-regulator/ DC-to-DC modules
• Voltage reference
• High efficiency linear power supplies
___________________________________________________________________________________________________________
Pin Configuration
1
2
3
TO-263-3
(MIC2940A-xxBU/WU)
1
2
3
TO-220-3
(MIC2940A-xxBT/WT)
MIC2940A Pinout
1) Input
2) Ground
3) Output
1
2 3
4
5
TO-263-5
(MIC2941ABU/WU)
MIC2941A Pinout
1) Adjust
2) Shutdown
3) Ground
4) Input
5) Output
1 2 3 4
5
TO-220-5
(MIC2941ABT/WT)
The TAB is Ground on 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
July 2007
M9999-071307
Micrel, Inc.
MIC2940A/2941A
Ordering Information
Part Number
Voltage
Temperature Range
Package
Lead Finish
MIC2940A-3.3BT
3.3V
–40° to +125°C
3-Pin TO-220
Standard
MIC2940A-3.3BU
3.3V
–40° to +125°C
3-Pin TO-263
Standard
MIC2940A-3.3WT
3.3V
–40° to +125°C
3-Pin TO-220
RoHS Comliant(1)
MIC2940A-3.3WU
3.3V
–40° to +125°C
3-Pin TO-263
RoHS Comliant(1)
MIC2940A-5.0BT
5V
–40° to +125°C
3-Pin TO-220
Standard
MIC2940A-5.0BU
5V
–40° to +125°C
3-Pin TO-263
Standard
MIC2940A-5.0WT
5V
–40° to +125°C
3-Pin TO-220
RoHS Comliant(1)
MIC2940A-5.0WU
5V
–40° to +125°C
3-Pin TO-263
RoHS Comliant(1)
MIC2940A-12BT
12V
–40° to +125°C
3-Pin TO-220
Standard
MIC2940A-12BU
12V
–40° to +125°C
3-Pin TO-263
Standard
MIC2940A-12WT
12V
–40° to +125°C
3-Pin TO-220
RoHS Comliant(1)
MIC2940A-12WU
12V
–40° to +125°C
3-Pin TO-263
RoHS Comliant(1)
MIC2941ABT
Adj.
–40° to +125°C
5-Pin TO-220
Standard
MIC2941ABU
Adj.
–40° to +125°C
5-Pin TO-263
Standard
MIC2941AWT
Adj.
–40° to +125°C
5-Pin TO-220
RoHS Comliant(1)
MIC2941AWU
Adj.
–40° to +125°C
5-Pin TO-263
RoHS Comliant(1)
Note:
1. RoHS compliant with ‘hot-melting solder’ exemption.
Schematic Diagram
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M9999-071307
Micrel, Inc.
MIC2940A/2941A
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
contact your local Micrel representative/distributor for
availability and specifications
Power Dissipation (Note 1) .......................Internally Limited
Lead Temperature (soldering, 5 sec.)........................ 260°C
Storage Temperature ................................–65°C to +150°C
Operating Junction Temperature ..............–40°C to +125°C
TO-220 (θJC) ........................................................2°C/W
TO-263 (θJC) ........................................................2°C/W
Input Supply Voltage ...................................... –20V to +60V
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.
Electrical Characteristics
Limits in standard typeface are for TJ = 25°C and limits in boldface apply over the full operating temperature range.
Unless otherwise specified, VIN = VOUT + 1V, IL = 1000mA, CL = 10µF. The MIC2941A is programmed to output 5V and
has VSHUTDOWN 0.6V.
Symbol
Parameter
VO
Output Voltage Accuracy
Condition
Min
5 mA ≤ IL ≤ 1A
–1
–2
–2.5
Typ
Max
Units
1
2
2.5
%
%
%
20
100
ppm/°C
∆VO
∆T
Output Voltage Temperature
Coefficient
(Note 2)
∆VO
VO
Line Regulation
IO = 10mA, (VOUT + 1V) ≤ VIN ≤ 26V
0.06
0.50
%
Load Regulation
IL = 5mA to 1.25A
IL = 5mA to 1A (Note 3)
0.04
0.16
0.20
%
%
VIN – VO
Dropout Voltage (Note 4)
IL = 5mA
60
IL = 250mA
200
IL = 1000mA
350
IL = 1250mA
400
150
180
250
320
450
600
600
mV
mV
mV
mV
mV
mV
mV
IL = 5mA
240
500
µA
IL = 250mA
3
IL = 1000mA
22
IL = 1250mA
35
4.5
6
35
45
70
mA
mA
mA
mA
mA
IGND
Ground Pin Current (Note 5)
IGNDDO
Ground Pin Current at Dropout
(Note 5)
VIN = 0.5V less than designed VOUT (VOUT 3.3)
IL = 5mA
330
600
µA
ILIMIT
Current Limit
VOUT = 0V (Note 6)
1.6
3.5
A
∆VO
∆PD
Thermal Regulation
(Note 7)
0.05
0.2
%/W
en
Output Noise Voltage
(10Hz to 100kHz)
IL = 100mA
CL = 10µF
CL = 33µF
400
260
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3
µVRMS
µVRMS
M9999-071307
Micrel, Inc.
MIC2940A/2941A
Electrical Characteristics (MIC2941A Only)
Parameter
Condition
Min
Typ
Max
Units
1.223
1.210
1.204
1.235
1.247
1.260
1.266
V
V
V
Adjust Pin Bias Current
20
40
60
nA
nA
Reference Voltage Temperature Coefficient
20
ppm/°C
Adjust Pin Bias Current Temperature
Coefficient
0.1
nA/°C
1.3
0.7
V
V
V
Reference Voltage
(Note 8)
Shutdown Input
Input Logic Voltage
Low (ON)
High (OFF)
Shutdown Pin Input Current
Regulator Output Current in Shutdown
2.0
VSHUTDOWN = 2.4V
30
50
100
µA
µA
VSHUTDOWN = 26V
450
600
750
µA
µA
3
30
60
µA
µA
(Note 10)
Notes:
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,
TJ(MAX), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient
temperature is calculated using: P(MAX) = (TJ(MAX) – TA) / θJA. Exceeding the maximum allowable power dissipation will result in excessive die
temperature, and the regulator will go into thermal shutdown.
2.
Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
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.
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.
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.
6.
The MIC2940A features fold-back current limiting. The short circuit (VOUT = 0V) current limit is less than the maximum current with normal output
voltage.
7.
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 200mA load pulse at VIN = 20V (a 4W pulse) for T = 10ms.
8.
VREF ≤ VOUT ≤ (VIN – 1 V), 4.3V ≤ VIN 26V, 5mA < IL ≤1.25A, TJ ≤TJ(MAX).
9.
Circuit of Figure 3 with R1 ≥ 150k Ω. VSHUTDOWN ≥ 2 V and VIN ≤ 26 V,VOUT = 0.
10. 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.
11. Maximum positive supply voltage of 60 V must be of limited duration (< 100 ms) and duty cycle (≤ 1%). The maximum continuous supply voltage is
26V.
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MIC2940A/2941A
Typical Characteristics
DROPOUT VOLTAGE (mV)
100
1
11
200
0
0
100
1000 10000
10A
OUTPUT CURRENT (mA)
0.30
0.20
ILOAD = 5mA
0.10
2.0
0.00
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
Fixed 3.3V Output Voltage
vs. Temperature
2 3 4 5 6 7
SUPPLY VOLTAGE (V)
Ground Current
vs. Temperature
ILOAD = 100mA
0.8
0.6
0.4
0.2
2.0
1.8
1.6
3.34
3.32
1.4
1.2
VOUT = VNOMINAL – 0.5V
1.0
VOUT = 0V
3.24
3.22
0.4
0.2
FIXED 3.3V
VERSION
3 SAMPLES
3.20
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
0.0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
July 2007
5
2
ILOAD = 1.25A
1
0
1
2
3
4
5
INPUT VOLTAGE (V)
6
Ground Current
vs. Supply Voltage
40
30
20
10
FIXED 3.3V DEVICE
ILOAD = 1.25A
0
2
4
6
8
INPUT VOLTAGE (V)
10
Ground Current
vs. Temperature
ILOAD = 1.25A
40
30
20
10
ILOAD = 100mA
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
Short Circuit and Maximum
Current vs. Temperature
0.8
0.6
3.28
3.26
3
50
1.4
1.2
1.0
ILOAD = 5mA
0
8
1.8
1.6
3.38
3.36
3.30
1
0.0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
CURRENT (A)
OUTPUT VOLTAGE (V)
3.40
FIXED 5V
ILOAD = 5mA
0
4
50
300
100
5
0
Ground Current
vs. Supply Voltage
400
Ground Current
vs. Temperature
0.40
ILOAD = 1.25A
200
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
GROUND CURRENT (µA)
10
0.1
400
1.25
Ground Current
vs. Output Current
40
GROUND CURRENT (mA)
0.25 0.50 0.75 1.00
OUTPUT CURRENT (A)
600
GROUND CURRENT (mA)
200
800
GROUND CURRENT (mA)
300
Dropout
Characteristics
6
Ground Current
vs. Input Voltage
1000
GROUND CURRENT (µA)
400
0
0.00
GROUND CURRENT (mA)
1000
GROUND CURRENT (mA)
DROPOUT VOLTAGE (mV)
500
Dropout Voltage
vs. Temperature
OUTPUT VOLTAGE (V)
Dropout Voltage
vs. Output Current
800
RLOAD = 100
600
400
200
0
-200
-30
-20 -10
0
10 20
INPUT VOLTAGE (V)
30
M9999-071307
Micrel, Inc.
MIC2940A/2941A
Typical Characteristics (continued)
50
VE N = 2V
25
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
MIC29402/3 Adjust Pin
Current vs. Temperature
OUTPUT (mV)
40
30
OUTPUT (mV)
0
5
TIME (ms)
10
100
COUT = 10 µF
20
0
-20
-200
2.0
1.5
1.0
5mA
0.5
0.0
-0.5
-5
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
INPUT (V)
8
6
4
-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
TIME (ms)
10
Line Transient
COUT = 100 µF
0
8
6
4
-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
TIME (ms)
1
0.1
1x106
1x100
0.01
100x103
ILOAD = 10mA
10x103
OUTPUT IMPEDANCE ( )
10
10
Output Impedance
vs. Frequency
1x103
ILOAD = 5mA
20
0
5
TIME (ms)
10
-10
100x100
10
COUT = 100 µF
0
10
-40
20
Load Transient
-100
Line Transient
40
10x100
ADJUST PIN CURRENT (nA)
50
-500
2.0
1.5
1.0
5mA
0.5
0.0
-0.5
-5
OUTPUT (A)
75
COUT = 10 µF
200
OUTPUT (mV)
VE N = 5V
OUTPUT (mV)
100
Load Transient
750
500
250
0
-250
INPUT (V)
ENABLE CURRENT (µA)
125
OUTPUT (A)
MIC29401/2 Shutdown Current
vs. Temperature
FREQUENCY (Hz)
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Micrel, Inc.
MIC2940A/2941A
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 relatively inefficient,
as increasing the capacitor from 1µF to 220µF only
decreases the noise from 430µV to 160µVRMS for a
100kHz bandwidth at 5V output. Noise can be reduced
by a factor of four with the MIC2941A by adding a
bypass capacitor across R1. Pick
Application Information
External Capacitors
A 10µF (or greater) capacitor is required between the
MIC2940A 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 3.3µF for current below 100mA or
2.2µF for currents below 10mA. Adjusting the MIC2941A
to voltages below 5V runs the error amplifier at lower
gains so that more output capacitance is needed. For
the worst-case situation of a 1.25A load at 1.23V output
(Output shorted to Adjust) a 22µF (or greater) capacitor
should be used.
The MIC2940A will remain stable and in regulation with
load currents ranging from 5mA on up to the full 1.25A
rating. The external resistors of the MIC2941A version
may be scaled to draw this minimum load current.
A 0.22µF capacitor should be placed from the
MIC2940A 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.
C BYPASS ≅
or about 0.01µF. When doing this, the output capacitor
must be increased to 22µF to maintain stability. These
changes reduce the output noise from 430µV to
100µVRMS 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.
Automotive Applications
The MIC2940A is ideally suited for automotive
applications for a variety of reasons. It will operate over
a wide range of input voltages with very low dropout
voltages (40mV at light loads), and very low quiescent
currents (240µA typical). These features are necessary
for use in battery powered systems, such as
automobiles. It is a “bulletproof” device 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.
Programming the Output Voltage (MIC2941A)
The MIC2941A may be programmed for any output
voltage between its 1.235V reference and its 26V
maximum rating. An external pair of resistors is required,
as shown in Figure 3.
VOUT = VREF x { 1 + R1/R2 } – |IFB| R1
where VREF is the nominal 1.235 reference voltage and
IFB is the Adjust pin bias current, nominally 20nA. The
minimum recommended load current of 1µA 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 = 100kΩ
reduces this error to 0.17% while increasing the resistor
program current to 12µA. Since the MIC2941A typically
draws 100µA at no load with SHUTDOWN opencircuited, this is a negligible addition.
July 2007
1
2πR 1 200Hz
4.75V
OUTPUT
VOLTAGE
ERROR
NOT *
VALID
NOT *
VALID
INPUT
VOLTAGE
5V
1.3V
Figure 1. ERROR Output Timing
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M9999-071307
Micrel, Inc.
MIC2940A/2941A
Typical Applications
V IN
+VIN
VIN
+VIN
VOUT = 5V
V OUT
+
VOUT
S HUTDOWN
INPUT
10µF
SHUTDOWN
OFF
GND
AD JU S T
26V
1.2V
V OUT
R1 100
pF
22µF
ON
1.23V
GND
V OUT = V R E F x (1 +
R1
)
R2
+5V to +7V
+V IN
+V IN
V IN
VOUT
SHUTDOWN
INPUT
V OUT = V IN
V CC OUT
VOUT
SHUTDOWN
OFF
+
ON
100pF
ADJ
GND
5V
ADJUST
3.3V
470 k
220k
1%
300k
10µF
1%
180k
1%
2N2222
Adjust Pin Low = Enable Output. Q1 ON = 3.3V, Q1 OFF = 5.0V.
* Minimum Input-Output Voltage Ranges from 40mV to 400mV,
depending on Load Current.
Figure 5. MIC2941A 5.0V or 3.3V Selectable Regulator
with Shutdown
Figure 4. MIC2941A Wide Input Voltage Range
Current Limit
July 2007
R2
Figure 3. MIC2941A Adjustable Regulator
Figure 2. MIC2940A-5.0 Fixed +5V Regulator
GND
VREF
8
M9999-071307
Micrel, Inc.
MIC2940A/2941A
Package Information
3-Pin TO-220 (T)
3-Pin TO-263 (U)
July 2007
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M9999-071307
Micrel, Inc.
MIC2940A/2941A
5-Pin TO-220 (T)
5-Pin TO-263 (U)
July 2007
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M9999-071307
Micrel, Inc.
MIC2940A/2941A
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
The 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.
© 2004 Micrel, Incorporated.
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