January 2002
1
MIC37300/01/02/37152
MIC37300/37301/37302
Micrel
MIC37300/37301/37302
3.0A, Low Voltage
Cap LDO Regulator
Final Information
General Description
The Micrel MIC37300/01/02 is a 3.0A low-dropout linear
voltage regulator that provides a low voltage, high current
output with a minimum of external components. It offers high
precision, ultra low dropout (500mV over temperature), and
low ground current.
The MIC37300/01/02 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, DSP, microcontroller,
etc.). It is available in fixed and adjustable output voltages.
Fixed voltages include 1.5V, 1.8V and 2.5V. The adjustable
version is capable of 1.24V to 5.5V.
Features of the MIC37300/01/02 LDO include thermal and
current limit protection, and reverse current & reverse battery
protection. Logic enable and error flag pins are available.
Junction temperature range of the MIC37300/01/02 is from
40
C to 125
C.
For applications requiring input voltage greater than 6.0V,
see MIC3910x, MIC3915x, MIC3930x, and MIC3950x LDOs.
Typical Application
VOUT
VIN
FLG
GND
VEN
C
OUT
47
F, Ceramic
100k
MIC37301
V
IN
= 3.0V
V
OUT
= 2.5V
C
IN
Fixed 2.5V Regulator with Error Flag
VOUT
VIN
ADJ
GND
VEN
C
OUT
47
F, Ceramic
R1
R2
1.3V
MIC37302
V
IN
C
IN
Adjustable Regulator
Features
3.0A minimum guaranteed output current
500mV maximum dropout voltage over temperature
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 and adjustable output voltages
Excellent line and load regulation specifications
Logic controlled shutdown
Thermal shutdown and current limit protection
Reverse-leakage protection
Low profile S-Pak package
Applications
LDO linear regulator for low-voltage digital IC
PC add-in cards
High efficiency linear power supplies
SMPS post regulator
Battery charger
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
SuperSwitcher and Super
eta PNP are trademarks of Micrel, Inc.
MIC37300/37301/37302
Micrel
MIC37300/01/02/37152
2
January 2002
Ordering Information
Output
Part Number
Current
Voltage*
Junction Temp. Range
Package
MIC37302BR
3.0A
ADJ.
40
C to +125
C
S-Pak
MIC37301-1.5BR
3.0A
1.5V
40
C to +125
C
S-Pak
MIC37301-1.8BR
3.0A
1.8V
40
C to +125
C
S-Pak
MIC37301-2.5BR
3.0A
2.5V
40
C to +125
C
S-Pak
*For other voltages contact Micrel.
Pin Configuration
TA
B
5
FLG/ADJ
4
VOUT
3
GND
2
VIN
1
EN
S-PAK5 (R)
Pin Description
Pin Number
Pin Name
Pin Function
1
EN
Enable (Input): CMOS compatible input. Logic high = enable, logic
low = shutdown
2
VIN
Input voltage which supplies current to the output power device.
3
GND
Ground (TAB is connected to ground on S-Pak)
4
VOUT
Regulator Output
5
FLG
Error Flag (Output): Open collector output. Active low indicates an output
fault condition.
ADJ
Adjustable regulator feedback input. Connect to resistor voltage divider.
January 2002
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MIC37300/01/02/37152
MIC37300/37301/37302
Micrel
Electrical Characteristics
T
A
= 25
C with V
IN
= V
OUT
+ 1V; V
EN
= V
IN
; I
L
= 10mA; 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 < Iout < I
L(max)
, Vout + 1
Vin
6V
-2
+2
%
Output Voltage Line Regulation
V
IN
= V
OUT
+1.0V to 6.0V, I
L
= 10mA
0.02
0.5
%
Output Voltage Load Regulation
I
L
= 10mA to 3A
0.2
1
%
V
IN
V
OUT
; Dropout Voltage ;
I
L
= 1.5A
175
350
mV
Note 5
I
L
= 3A
310
500
mV
Ground Pin Current, Note 6
I
L
= 3A
27
40
mA
50
mA
Ground Pin Current in Shutdown
V
IL
< 0.5V, V
IN
= V
OUT
+ 1V
1.0
5
A
Current Limit
V
OUT
= 0
4.75
6.5
A
Start-up Time
V
EN
= V
IN
, I
OUT
= 10mA, C
OUT
= 47
F
170
500
s
Enable Input
Enable Input Threshold
Regulator enable
2.25
V
Regulator shutdown
0.8
V
Enable Pin Input Current
V
IL
< 0.8V (Regulator shutdown)
2
A
4
A
V
IH
> 2.25V (Regulator enabled)
1
15
30
A
75
A
Flag Output
I
FLG(LEAK)
V
OH
= 6V
1
A
2
A
V
FLG(LO)
V
IN
= 2.25V, I
OL
= 250uA, Note 7
210
400
mV
500
mV
V
FLG
Low Threshold, % of Vout below nominal
93
%
Hysteresis
2
%
High Threshold, % of Vout below nominal
99.2
%
MIC37302 only
Reference Voltage
1.228
1.240
1.252
V
1.215
1.265
V
Adjust Pin Bias Current
40
80
nA
120
nA
Absolute Maximum Rating (Note 1)
Supply Voltage (V
IN
) .................................................... 6.5V
Enable Input Voltage (V
EN
) .......................................... 6.5V
Power Dissipation .................................... Internally Limited
Junction Temperature ........................ 40
C
T
J
+125
C
Storage Temperature ......................... 65
C
T
J
+150
C
Lead Temperature (soldering, 5 sec.) ....................... 260
C
ESD, Note 3
Operating Maximum Rating (Note 2)
Supply Voltage (V
IN
) ..................................... 2.25V to 6.0V
Enable Input Voltage (V
EN
) ................................ 0V to 6.0V
Junction Temperature Range ............. 40
C
T
J
+125
C
Maximum Power Dissipation ................. ............... Note 4
Package Thermal Resistance
S-Pak(
JC
) ........................ ............. ............2
C/W
MIC37300/37301/37302
Micrel
MIC37300/01/02/37152
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January 2002
Note 1.
Exceeding the absolute maximum ratings may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Device is ESD sensitive. Handling precautions recommended.
Note 4.
P
D(MAX)
= (T
J(MAX)
T
A
) /
JA
, where
JA
, depends upon the printed icurcuit layout. See "Applications Information."
Note 5.
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.
Note 6.
I
GND
is the quiescent current. I
IN
= I
GND
+ I
OUT
.
Note 7.
For a 2.5V device, V
IN
= 2.250V (device is in dropout).
January 2002
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MIC37300/01/02/37152
MIC37300/37301/37302
Micrel
Applications Information
The MIC37300/01/02 is a high-performance low-dropout
voltage regulator suitable for moderate to high-current regu-
lator 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-emiiter 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 MIC37300/01/02 regulator is fully protected from dam-
age 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 temperature exceeds the maximum safe operating tem-
perature. 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
o
C and
CS
is between 0
o
C and 2
o
C/W.
The heat sink may be significantly reduced in applications
where the minimum input votlage 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 MIC37300/01/02 requires an output capacitor for stable
operation. As a
Cap LDO, the MIC37300/01/02 can operate
with ceramic output capacitors as long as the amount of
capacitance is 47
F or greater. For values of output capaci-
tance lower than 47
F, the recommended ESR range is
200m
to 2
. The minimum value of output capacitance
recommended for the MIC37300 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 tran-
sient response and noise reduction at high frequency. X7R/
X5R dielectric-type ceramic capacitors are recommended
because of their temperature performance. X7R-type capaci-
tors change capacitance by 15% over their operating tem-
perature 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 capacitor with
Y5V dielectric, the value must be much higher than an X7R
ceramic capacitor to ensure the same minimum capacitance
over the equivalent operating temperature range. The
MIC37300/01/02 has excellent transient response to varia-
tions 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 47
F output
capacitor, is all that is required. Larger values help to improve
performance even further.
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 ad supply
capacitance, or when the supply is a battery. Small, surface-
mount chip capacitors can be used for the bypassing. The
capacitor should be place within 1" of the device for optimal
performance. Larger values will help to improve ripple rejec-
tion 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 MIC37300/01/02 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.
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 MIC37300/01/02 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.
MIC37300/37301/37302
Micrel
MIC37300/01/02/37152
6
January 2002
Minimum Load Current
The MIC37300/01/02 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.
Error Flag
The MIC37301 features an error flag circuit that monitors the
output voltage and signals an error condition when the
voltage 5% below the nominal output voltage. The error flag
is an open-collector output that can sink 10mA during a fault
condition.
Low output voltage can be caused by a number of problems,
including an overcurrent fault (device in current limit) or low
input voltage. The flag is inoperative during overtemperature
shutdown.
Enable Input
The MIC37301/37302 also features an enable input for on/off
control of the device. Its shutdown state draws "zero" current
(only micoamperes of leakage). The enable input is TTL/
CMOS compatible for simple logic interface, but can be
connected to up to V
IN
. When enabled, it draws approxi-
mately 15
A.
Adjustable Regulator Design
IN
R1
V
OUT
V
IN
C
OUT
R2
EN
OUT
ADJ
GND
MIC37302
ENABLE
SHUTDOWN
V
1.240V 1
R1
R2
OUT
=
+
Figure 2. Adjustable Regulator with Resistors
The MIC37302 allows programming the output voltage any-
where between 1.24V and the 5.5V maximum operating
rating of the family. Two resistors are used. Resistors can be
quite large, up to 1M
, because of the very high input
impedance and low bias current of the sense comparator:
The resistor values are calculated by:
R1 R2
V
1.240
1
OUT
=
-
Where V
OUT
is the desired output voltage. Figure 2 shows
component definition. Applications with widely varying load
currents may scale the resistors to draw the minimum load
current required for proper operation (see above).
January 2002
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MIC37300/01/02/37152
MIC37300/37301/37302
Micrel
Package Information
0.370
0.005
9.395
0.125
0.355
0.005
9.015
0.125
0.315
0.005
8.000
0.130
0.415
0.005
10.54
0.130
0.028
0.003
0.710
0.080
0.075
0.005
1.905
0.125
0.040
0.005
1.015
0.125
0.003
0.002
0.080
0.050
0.036
0.005
0.915
0.125
INCHES
MILLIMETER
0
min
6
max
0.010
0.250
0.010
0.250
0.067
1.700
0.040
0.010
1.015
0.255
0.256
6.50
5-Lead S-PAK (R)
MIC37300/37301/37302
Micrel
MIC37300/01/02/37152
8
January 2002
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
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
2002 Micrel Incorporated
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