November 2003
1
M9999-112003
MIC37139
Micrel
MIC37139
1.5A, Low-Voltage
Cap LDO Regulator
General Description
The Micrel MIC37139 is a 1.5A low-dropout linear voltage
regulator that provides a low-voltage, high-current output
with a minimum of external components. It offers high preci-
sion, ultra-low dropout (500mV overtemperature), and low
ground current.
The MIC37139 operates from an input of 2.25V to 6.0V. It is
designed to drive digital circuits requiring low-voltage at high
currents (i.e., PLDs, DSPs, microcontrollers, etc.). It is avail-
able in fixed output voltages, including 1.5V, 1.65V, 1.8V,
2.5V and 3.3V.
Features of the MIC37139 LDO include thermal and current-
limit protection, and reverse-current and reverse-battery
protection.
Junction temperature range of the MIC37139 is from 40
C
to +125
C.
All support documentation can be found on Micrel's web
site at www.micrel.com.
Typical Application
IN
1.8V
V
IN
3.3V
10
F
ceramic
OUT
GND
MIC37139
1.8V/1.5A Regulator
Features
1.5A minimum guaranteed output current
500mV maximum dropout voltage overtemperature
Ideal for 3.0V to 2.5V conversion
Ideal for 2.5V to 1.8V, 1.65V, or 1.5V conversion
Stable with ceramic or tantalum capacitor
Wide input voltage range:
V
IN
: 2.25V to 6.0V
+1.0% initial output tolerance
Fixed 1.8V output voltage
Excellent line and load regulation specifications
Thermal shutdown and current-limit protection
Reverse-leakage protection
Low profile SOT-223 package
Applications
LDO linear regulator for low-voltage digital IC
PC add-in cards
High-efficiency linear power supplies
SMPS post regulator
Battery charger
Set-top boxes
Digital video recorders
PowerPC
power supplies
Multimedia and PC processor supplies
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
Super eta PNP is a registered trademark of Micrel, Inc.
PowerPC is a registered trademark of IBM Corporation.
MIC37139
Micrel
M9999-112003
2
November 2003
Pin Configuration
GND
IN
OUT
1
3
2
TAB
OUT
SOT-223 (S)
Ordering Information
Output
Part Number
Current
Voltage
Junction Temp. Range
Package
MIC37139-1.8BS
1.5A
1.8V
40
C to +125
C
SOT-223
Pin Description
Pin Number
Pin Name
Pin Function
1
GND
Ground.
2
OUT
Regulator Output.
3
IN
Supply (Input).
November 2003
3
M9999-112003
MIC37139
Micrel
Electrical Characteristics
(5)
T
A
= 25
C with V
IN
= V
OUT
+ 1V; V
EN
= V
IN
; bold values indicate 40
C < T
J
< +125
C; unless otherwise noted.
Parameter
Condition
Min
Typ
Max
Units
Output Voltage Accuracy
I
L
= 10mA
1
+1
%
10mA < I
OUT
< I
L
(max), V
OUT
+ 1
V
IN
6V
2
+2
%
Output Voltage Line Regulation
V
IN
= V
OUT
+1.0V to 6.0V
0.06
0.5
%
Output Voltage Load Regulation
I
L
= 10mA to 1.5A
0.2
1
%
V
IN
V
OUT
; Dropout Voltage
(6)
I
L
= 750mA
350
mV
I
L
= 1.5A
500
mV
Ground Pin Current
(7)
I
L
= 1.5A
17
30
mA
Ground Pin Current in Shutdown
V
IL
0.5V, V
IN
= V
OUT
+ 1V
1.0
A
Current Limit
V
OUT
= 0
2.25
4.0
A
Notes:
1.
Exceeding the absolute maximum ratings may damage the device.
2.
The device is not guaranteed to function outside its operating rating.
3.
P
D
(max) = (T
J
(max) T
A
)
JA
, where
JA
, depends upon the printed circuit layout. See
"Applications Information."
4.
Device is ESD sensitive. Handling precautions recommended.
5.
Specification for packaged product only.
6.
V
DO
= V
IN
V
OUT
when V
OUT
decreased to 98% of its nominal output voltage with V
IN
= V
OUT
+1V. For output voltages below 1.75V, dropout
voltage specification does not apply due to a minimum input operating voltage of 2.25V.
7.
I
GND
is the quiescent current. I
IN
= I
GND
+ I
OUT
.
Absolute Maximum Rating
(1)
Supply Voltage (V
IN
) .................................................... 6.5V
Enable Input Voltage (V
EN
) .......................................... 6.5V
Power Dissipation .................................... Internally Limited
Junction Temperature (T
J
) ................. 40
C
T
J
+125
C
Storage Temperature (T
S
) ................. 65
C
T
J
+150
C
Lead Temperature (soldering, 5 sec.) ....................... 260
C
ESD
(4)
Operating Maximum Rating
(2)
Supply Voltage (V
IN
) ..................................... 2.25V to 6.0V
Enable Input Voltage (V
EN
) ................................ 0V to 6.0V
Junction Temperature (T
J
) ................. 40
C
T
J
+125
C
Maximum Power Dissipation
(3)
Package Thermal Resistance
SOT-223(
JC
) .................................................. 15
C/W
MIC37139
Micrel
M9999-112003
4
November 2003
Typical Characteristics
0
20
40
60
80
1E-2 1E-1 1E+0 1E+1 1E+2 1E+3
PSRR (dB)
FREQUENCY (Hz)
Power Supply
Rejection Ratio
I
OUT
= 1.5A
C
OUT
= 10
F
C
IN
= 0
V
IN
= 3.3V
V
OUT
= 2.5V
0.01 0.1
1
10
100
1k
0
20
40
60
80
1E-2 1E-1 1E+0 1E+1 1E+2 1E+3
PSRR (dB)
FREQUENCY (Hz)
Power Supply
Rejection Ratio
I
OUT
= 1.5A
C
OUT
= 47
F
C
IN
= 0
V
IN
= 3.3V
V
OUT
= 2.5V
0.01 0.1
1
10
100
1k
0
50
100
150
200
250
300
350
0
400
800
1200
1600
DROPOUT VOLTAGE (mV)
OUTPUT CURRENT (mA)
Dropout Voltage vs.
Output Current
2.5V
OUT
0
50
100
150
200
250
300
350
400
450
500
-40 -20 0
20 40 60 80 100 120
DROPOUT VOLTAGE (mV)
TEMPERATURE (
C)
Dropout Voltage vs.
Temperature
2.5V
OUT
0
0.5
1.0
1.5
2.0
2.5
3.0
1
1.5
2
2.5
3
3.5
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Dropout Characteristics
100mA
750mA
1.5A
0
2
4
6
8
10
12
14
16
18
0
200
400
600
800
1000
1200
1400
1600
GROUND CURRENT (mA)
OUTPUT CURRENT (mA)
Ground Current
vs. Output Current
1.5V
OUT
2.5V
OUT
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0
1
2
3
4
5
6
GROUND CURRENT (mA)
SUPPLY VOLTAGE (V)
Ground Current
vs. Supply Voltage
V
OUT
= 2.5V
10mA
100mA
0
5
10
15
20
25
30
35
40
45
0
1
2
3
4
5
6
GROUND CURRENT (mA)
SUPPLY VOLTAGE (V)
Ground Current
vs. Supply Voltage
V
OUT
= 2.5V
1500mA
750mA
1000mA
0.4
0.405
0.41
0.415
0.42
0.4
0.43
0.435
0.44
0.445
0.5
-40 -20 0
20 40 60 80 100 120
GROUND CURRENT (mA)
TEMPERATURE (
C)
Ground Current
vs. Temperature
V
OUT
= 2.5V
I
LOAD
= 10mA
0
2
4
6
8
10
12
14
16
18
20
-40 -20 0
20 40 60 80 100 120
GROUND CURRENT (mA)
TEMPERATURE (
C)
Ground Current
vs. Temperature
V
OUT
=2.5V
I
LOAD
= 1.5A
0
0.5
1.0
1.5
2.0
2.5
3.0
-40 -20 0
20 40 60 80 100 120
SHORT CIRCUIT CURRENT (mA)
TEMPERATURE (
C)
Short Circuit Current
vs. Temperature
0
1
2
3
4
5.0
6
7
-40 -20 0
20 40 60 80 100 120
GROUND CURRENT (mA)
TEMPERATURE (
C)
Ground Current
vs. Temperature
V
OUT
= 2.5V
I
LOAD
= 750mA
November 2003
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M9999-112003
MIC37139
Micrel
2.40
2.42
2.44
2.46
2.48
2.50
2.52
2.54
2.56
2.58
2.60
-40 -20 0
20 40 60 80 100 120
OUTPUT VOLTAGE (V)
TEMPERATURE (
C)
Output Voltage
vs. Temperature
MIC37139
Micrel
M9999-112003
6
November 2003
Functional Characteristics
TIME (400 s/div.)
OUTPUT
CURRENT
(1A/div
.
)
OUTPUT
VOL
T
AGE
(50mV/div
.
)
V
IN
= 3.3V
V
OUT
= 2.5V
C
OUT
= 47 F
Load Transient Response
10mA
1.5A
Load Transient Response
TIME (400 s/div.)
LOAD CURRENT
(1A/div
.
)
OUTPUT
VOL
T
AGE
(50mV/div
.
)
5V
3.3V
V
IN
= 3.3V
V
OUT
= 2.5
C
OUT
= 10 F
1.5A
100mA
TIME (250 s/div.)
INPUT
VOL
T
AGE
(2V/div
.
)
OUTPUT
VOL
T
AGE
(20mV/div
.
)
V
OUT
= 2.5V
C
OUT
= 10 F
Line Transient Response
3.3V
5V
November 2003
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M9999-112003
MIC37139
Micrel
Functional Diagram
Ref.
Thermal
Shut-
down
1.240V
IN
OUT
MIC37139 Fixed Regulator Block Diagram
MIC37139
Micrel
M9999-112003
8
November 2003
Applications Information
The MIC37139 is a high-performance low-dropout voltage
regulator suitable for moderate to high-current regulator
applications. Its 500mV dropout voltage at full load and
overtemperature makes it especially valuable in battery-
powered systems and as high-efficiency noise filters in post-
regulator applications. Unlike older NPN-pass transistor de-
signs, there the minimum dropout voltage is limited by the
based-to-emitter voltage drop and collector-to-emitter satu-
ration voltage, dropout performance of the PNP output of
these devices is limited only by the low V
CE
saturation
voltage.
A trade-off for the low-dropout voltage is a varying base drive
requirement. Micrel's Super eta PNP
process reduces this
drive requirement to only 2% to 5% of the load current.
The MIC37139 regulator is fully protected from damage due
to fault conditions. Current limiting is provided. This limiting is
linear; output current during overload conditions is constant.
Thermal shutdown disables the device when the die tem-
perature exceeds the maximum safe operating temperature.
Transient protection allows device (and load) survival even
when the input voltage spikes above and below nominal. The
output structure of these regulators allows voltages in excess
of the desired output voltage to be applied without reverse
current flow.
Thermal Design
Linear regulators are simple to use. The most complicated
design parameters to consider are thermal characteristics.
Thermal design requires the following application-specific
parameters:
Maximum ambient temperature (T
A
)
Output current (I
OUT
)
Output voltage (V
OUT
)
Input voltage (V
IN
)
Ground current (I
GND
)
First, calculate the power dissipation of the regulator from
these numbers and the device parameters from this datasheet.
P
D
= (V
IN
V
OUT
) I
OUT
+ V
IN
I
GND
where the ground current is approximated by using numbers
from the
"Electrical Characteristics"
or
"Typical Characteris-
tics."
Then, the heat sink thermal resistance is determined
with this formula:
SA
=
(
(T
J
(max) T
A
)/ P
D
)
(
JC
+
CS
)
Where T
J
(max)
125
C and
CS
is between 0
C and 2
C/W.
The heat sink may be significantly reduced in applications
where the minimum input voltage is known and is large
compared with the dropout voltage. Use a series input
resistor to drop excessive voltage and distribute the heat
between this resistor and the regulator. The low dropout
properties of Micrel Super eta PNP
regulators allow signifi-
cant reductions in regulator power dissipation and the asso-
ciated heat sink without compromising performance. When
this technique is employed, a capacitor of at least 1.0
F is
needed directly between the input and regulator ground.
Refer to
"Application Note 9"
for further details and examples
on thermal design and heat sink applications.
Output Capacitor
The MIC37139 requires an output capacitor for stable opera-
tion. As a
Cap LDO, the MIC37139 can operate with ceramic
output capacitors as long as the amount of capacitance is
47
F or greater. For values of output capacitance lower than
47
F, the recommended ESR range is 200m
to 2
. The
minimum value of output capacitance recommended for the
MIC37139 is 10
F.
For 47
F or greater, the ESR range recommended is less
than 1
. Ultra-low ESR ceramic capacitors are recommended
for output capacitance of 47
F or greater to help improve
transient response and noise reduction at high frequency.
X7R/X5R dielectric-type ceramic capacitors are recom-
mended because of their temperature performance. X7R-
type capacitors change capacitance by 15% over their op-
erating temperature range and are the most stable type of
ceramic capacitors. Z5U and Y5V dielectric capacitors change
value by as much as 50% and 60%, respectively, over their
operating temperature ranges. To use a ceramic chip capaci-
tor with Y5V dielectric, the value must be much higher than an
X7R ceramic capacitor to ensure the same minimum capaci-
tance over the equivalent operating temperature range.
MIC37139
IN
OUT
GND
C
IN
C
OUT
V
IN
V
OUT
Figure 1. Capacitor Requirements
Input Capacitor
An input capacitor of 1.0
F or greater is recommended when
the device is more than 4 inches away from the bulk and
supply capacitance, or when the supply is a battery. Small,
surface-mount chip capacitors can be used for the bypass-
ing. The capacitor should be place within 1" of the device for
optimal performance. Larger values will help to improve
ripple rejection by bypassing the input to the regulator, further
improving the integrity of the output voltage.
Transient Response and 3.3V to 2.5V, 2.5V to 1.8V or
1.65V, or 2.5V to 1.5V Conversions
The MIC37139 has excellent transient response to variations
in input voltage and load current. The device has been
designed to respond quickly to load current variations and
input voltage variations. Large output capacitors are not
required to obtain this performance. A standard 10
F output
capacitor, preferably tantalum, is all that is required. Larger
values help to improve performance even further.
November 2003
9
M9999-112003
MIC37139
Micrel
By virtue of its low-dropout voltage, this device does not
saturate into dropout as readily as similar NPN-based de-
signs. When converting from 3.3V to 2.5V, 2.5V to 1.8V or
1.65V, or 2.5V to 1.5V, the NPN-based regulators are already
operating in dropout, with typical dropout requirements of
1.2V or greater. To convert down to 2.5V without operating in
dropout, NPN-based regulators require an input voltage of
3.7V at the very least. The MIC37139 regulator will provide
excellent performance with an input as low as 3.0V or 2.25V,
respectively. This gives the PNP-based regulators a distinct
advantage over older, NPN-based linear regulators.
Minimum Load Current
The MIC37139 regulator is specified between finite loads. If
the output current is too small, leakage currents dominate
and the output voltage rises. A 10mA minimum load current
is necessary for proper operation.
MIC37139
Micrel
M9999-112003
10
November 2003
Package Information
16
10
0.84 (0.033)
0.64 (0.025)
1.04 (0.041)
0.85 (0.033)
2.41 (0.095)
2.21 (0.087)
4.7 (0.185)
4.5 (0.177)
6.70 (0.264)
6.30 (0.248)
7.49 (0.295)
6.71 (0.264)
3.71 (0.146)
3.30 (0.130)
3.15 (0.124)
2.90 (0.114)
10
MAX
0.10 (0.004)
0.02 (0.0008)
0.38 (0.015)
0.25 (0.010)
C
L
DIMENSIONS:
MM (INCH)
C
L
1.70 (0.067)
1.52 (0.060)
0.91 (0.036) MIN
SOT-223 (S)
MICREL, INC.
1849 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
http://www.micrel.com
The information furnished by Micrel in this datasheet 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 at Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
2003 Micrel, Incorporated.
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