January 2002
1
MIC37500/37501/37502
MIC37500/37501/37502
Micrel
MIC37500/37501/37502
5A, Low Voltage
Cap LDO Regulator
Advance Information
General Description
The Micrel MIC37500/01/02 is a 5A low-dropout linear volt-
age regulator that provides a low voltage, high current output
with a minimum of external components. It offers high preci-
sion, ultra low dropout (500mV), and low ground current.
The MIC37500/01/02 operates from an input of 2.3V 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. The adjustable version is capable of
1.24V to 5.5V.
Features of the MIC37500/01/02 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 MIC37500/01/02 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
VOUT
VIN
FLG
GND
VEN
C
OUT
100
F, Ceramic
100k
MIC37500
V
IN
= 3.0V
V
OUT
= 2.5V
C
IN
Fixed 2.5V Regulator with Error Flag
Features
5A minimum guaranteed output current
500mV maximum dropout voltage
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
: 2.3V 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 is a trademark of Micrel, Inc.
VOUT
VIN
VOUT
VIN
ADJ
GND
VEN
C
OUT
100
F, Ceramic
R1
R2
1.3V
MIC37502
V
IN
C
IN
Adjustable Regulator
MIC37500/37501/37502
Micrel
MIC37500/37501/37502
2
January 2002
Ordering Information
Output
Part Number
Current
Voltage*
Junction Temp. Range
Package
MIC37502BR
5A
ADJ.
40
C to +125
C
S-Pak-7
MIC37501-1.5BR
5A
1.5V
40
C to +125
C
S-Pak-7
*For other voltages contact Micrel.
Pin Configuration
TA
B
7
FLG/ADJ
6
VOUT
5
VOUT
4
GND
3
VIN
2
VIN
1
EN
S-PAK7
Pin Description
Pin Number
Pin Name
Pin Function
1
EN
Enable (Input): CMOS compatible input. Logic high = enable, logic
low = shutdown
2, 3
VIN
Input voltage which supplies current to the output power device. Connect
pins 2 and 3 together externally.
4
GND
Ground (TAB is connected to ground on S-Pak)
5, 6
VOUT
Regulator Output. Connect pins 5 and 6 together externally.
7
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
3
MIC37500/37501/37502
MIC37500/37501/37502
Micrel
Electrical Characteristics
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 5A
0.2
1
%
V
IN
V
OUT
; Dropout Voltage ;
I
L
= 2.5A
350
mV
Note 5
I
L
= 5A
330
500
mV
Ground Pin Current, Note 6
I
L
= 5A
57
mA
Ground Pin Current in Shutdown
V
IL
< 0.5V, V
IN
= V
OUT
+ 1V
1.0
A
Current Limit
V
OUT
= 0
7.5
A
Start-up Time
V
EN
= V
IN
, I
OUT
= 10mA, C
OUT
= 22
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
mV
mV
V
FLG
Low Threshold, % of Vout below nominal
93
%
Hysteresis
2
%
High Threshold, % of Vout below nominal
99.2
%
MIC37502 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
) ....................................... 2.3V 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
MIC37500/37501/37502
Micrel
MIC37500/37501/37502
4
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 2.3V.
Note 6.
I
GND
is the quiescent current. I
IN
= I
GND
+ I
OUT
.
Note 7.
For a 2.5V device, V
IN
= 2.3V (device is in dropout).
January 2002
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MIC37500/37501/37502
MIC37500/37501/37502
Micrel
Applications Information
The MIC37500/01/02 is a high-performance low-dropout
voltage regulator suitable for moderate to high-current regu-
lator applications. Its 500mV dropout voltage at full load
makes it especially valuable in battery-powered systems and
as high-efficiency noise filters in post-regulator applications.
Unlike older NPN-pass transistor designs, there the minimum
dropout voltage is limited by the based-to-emiiter voltage
drop and collector-to-emitter saturation voltage, dropout per-
formance 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 Beta PNPTM process reduces
this drive requirement to only 2% to 5% of the load current.
The MIC37500/01/02 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) sur-
vival 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 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 Beta 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 MIC37500/01/02 requires an output capacitor for stable
operation. As a
Cap LDO, the MIC37500/01/02 can operate
with ceramic output capacitors as long as the amount of
capacitance is 100
F or greater. For values of output capaci-
tance lower than 100
F, the recommended ESR range is
200m
to 2
. The minimum value of output capacitance
recommended for the MIC37500/01/02 is 47
F.
For 100
F or greater the ESR range recommended is less
than 1
ultra-low ESR ceramic capacitors are recommended
for output capacitance of 100
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. The
MIC37500/01/02 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 MIC37500/01/02 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 47
F output
capacitor, 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 MIC37500/01/02 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.
MIC37500/37501/37502
Micrel
MIC37500/37501/37502
6
January 2002
Minimum Load Current
The MIC37500/01/02 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 MIC37501 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 MIC37501/37502 also feature 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
MIC37502
ENABLE
SHUTDOWN
V
1.240V 1
R1
R2
OUT
=
+
Figure 2. Adjustable Regulator with Resistors
The MIC37502 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
7
MIC37500/37501/37502
MIC37500/37501/37502
Micrel
Package Information
SCALE 20:1
0.375 (9.52)
0.365 (9.27)
0.360 (9.14)
0.350 (8.89)
0.080 (2.03)
0.070 (1.78)
0.010 BSC
(0.25 BSC)
0.045 (1.14)
0.035 (0.89)
0.316 BSC
(8.03 BSC)
0.256 BSC
(6.50 BSC)
0.031 (0.79)
0.025 (0.63)
0.005 (0.13)
0.001 (0.03)
6
0
0.010 BSC
(0.25 BSC)
0.050 BSC
(1.27 BSC)
0.420 (10.67)
0.410 (10.41)
0.050 (1.27)
0.030 (0.76)
0.320 (8.13)
0.310 (7.87)
DIMENSIONS:
INCH (MM)
7-Lead S-PAK (R)
MIC37500/37501/37502
Micrel
MIC37500/37501/37502
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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