July 2003 1 MIC37500/37501/37502
MIC37500/37501/37502 Micrel
MIC37500/37501/37502
5A, Low Voltage µCap LDO Regulator
General Description
The MIC37500/01/02 is a 5A 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), 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, DSPs, microcontrollers, etc.). It is
available in fixed and adjustable output voltages. Fixed
voltages include 1.5V, 1.65V, 1.8V, 2.5V and 3.3V. 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 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.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Typical Application
VOUTVIN
VOUTVIN
FLG
GND
VEN
C
OUT
100µF, Ceramic
100k
MIC37501
V
IN
= 3.0V V
OUT
= 2.5V
C
IN
Fixed 2.5V Regulator with Error Flag
VOUTVIN
VOUTVIN
ADJ
GND
VEN C
OUT
100µF, Ceramic
R1
R2
1.3V
MIC37502
V
IN
C
IN
Adjustable Regulator
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:
VIN: 2.3V to 6.0V
•±1.0% initial output tolerance
•Fixed and adjustable output voltages
MIC37500—3 terminal fixed voltage
MIC37501—5 terminal fixed voltage
MIC37502—5 terminal adjustable voltage
•Excellent line and load regulation specifications
•Logic controlled shutdown
•Thermal shutdown and current limit protection
•Reverse-leakage protection
•Low profile S-Pak and TO-263 packages
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
0
50
100
150
200
250
300
350
400
450
012345
DROPOUT (mV)
OUTPUT CURRENT (A)
Dropout
vs. Output Current
2.5VOUT
MIC37500/37501/37502 Micrel
MIC37500/37501/37502 2 July 2003
Ordering Information
Output
Part Number Current Voltage* Junction Temp. Range Package
MIC37500-1.5BR 5A 1.5V –40°C to +125°C S-Pak-5
MIC37500-1.65BR 5A 1.65V –40°C to +125°C S-Pak-5
MIC37500-1.8BR 5A 1.8V –40°C to +125°C S-Pak-5
MIC37500-2.5BR 5A 2.5V –40°C to +125°C S-Pak-5
MIC37500-3.3BR 5A 3.3V –40°C to +125°C S-Pak-5
MIC37501-1.5BR 5A 1.5V –40°C to +125°C S-Pak-7
MIC37501-1.65BR 5A 1.65V –40°C to +125°C S-Pak-7
MIC37501-1.8BR 5A 1.8V –40°C to +125°C S-Pak-7
MIC37501-2.5BR 5A 2.5V –40°C to +125°C S-Pak-7
MIC37501-3.3BR 5A 3.3V –40°C to +125°C S-Pak-7
MIC37502BR 5A ADJ. –40°C to +125°C S-Pak-7
MIC37502BU 5A ADJ –40°C to +125°C TO-263-5
*For other voltages contact Micrel.
Pin Configurations
TAB
5 VOUT
4 VOUT
3 GND
2 VIN
1 VIN
S-PAK-5
Pin Descriptions
Pin Number Pin Number Pin Number Pin Name Pin Function
TO-263-5 S-PAK-5 S-PAK-7
1—1 EN Enable (Input): CMOS compatible input. Logic high = enable, logic
low = shutdown
2 1, 2 2, 3 VIN Input voltage which supplies current to the output power device. Connect
pins 2 and 3 together externally.
3 3 4 GND Ground (TAB is connected to ground on S-Pak)
4 4, 5 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.
5—7 ADJ Adjustable regulator feedback input. Connect to resistor voltage divider.
TAB
7 FLG/ADJ
6 VOUT
5 VOUT
4 GND
3 VIN
2 VIN
1EN
S-PAK-7
TAB
5 ADJ
4 VOUT
3 GND
2 VIN
1EN
TO-263-5
July 2003 3 MIC37500/37501/37502
MIC37500/37501/37502 Micrel
Electrical Characteristics (Note 5)
TA = 25°C with VIN = VOUT + 1V; VEN = VIN; bold values indicate –40°C < TJ < +125°C; unless otherwise noted.
Parameter Condition Min Typ Max Units
Output Voltage Accuracy IL = 10mA –1+1%
10mA < IOUT < IL(max), VOUT + 1 ≤ VIN ≤ 6V –2+2%
Output Voltage Line Regulation VIN = VOUT +1.0V to 6.0V 0.06 0.5 %
Output Voltage Load Regulation IL = 10mA to 5A 0.2 1%
VIN – VOUT, Dropout Voltage, IL = 2.5A 350 mV
Note 6 IL = 5A 330 500 mV
Ground Pin Current, Note 7 IL = 5A 57 100 mA
Ground Pin Current in Shutdown VIL < 0.5V, VIN = VOUT + 1V 1.0 µA
Current Limit VOUT = 0 5 7.5 10 A
Start-up Time VEN = VIN, IOUT = 10mA, COUT = 100µF 170 500 µs
Enable Input
Enable Input Threshold Regulator enable 2.25 V
Regulator shutdown 0.8 V
Enable Pin Input Current VIL < 0.8V (Regulator shutdown) 2 µA
4µA
VIH > 2.25V (Regulator enabled) 1 15 30 µA
75 µA
Flag Output
IFLG(LEAK) VOH = 6V 1µA
2µA
VFLG(LO) VIN = 2.25V, IOL = 250µA, Note 8 210 400 mV
500 mV
VFLG 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 (VIN) ....................................................6.5V
Enable Input Voltage (VEN) ..........................................6.5V
Power Dissipation ....................................Internally Limited
Junction Temperature ........................–40°C ≤ TJ ≤ +125°C
Storage Temperature ........................ –65°C ≤ TJ ≤ +150°C
Lead Temperature (soldering, 5 sec.) ....................... 260°C
ESD, Note 3
Operating Maximum Rating (Note 2)
Supply Voltage (VIN) ....................................... 2.3V to 6.0V
Enable Input Voltage (VEN) ................................ 0V to 6.0V
Junction Temperature Range............ –40°C ≤ TJ ≤ +125°C
Maximum Power Dissipation.................................... Note 4
Package Thermal Resistance
S-Pak(θJC).........................................................2°C/W
TO-263(θJC) ......................................................2°C/W
MIC37500/37501/37502 Micrel
MIC37500/37501/37502 4 July 2003
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. PD(MAX) = (TJ(MAX) – TA) / θJA, where θJA, depends upon the printed circuit layout. See
“Applications Information.”
Note 5. Specification for packaged product only.
Note 6. VDO = VIN – VOUT when VOUT decreased to 98% of its nominal output voltage with VIN = VOUT +1V. For output voltages below 1.75V, dropout
voltage specification does not apply due to a minimum input operating voltage of 2.3V.
Note 7. IGND is the quiescent current. IIN = IGND + IOUT.
Note 8. For a 2.5V device, VIN = 2.3V (device is in dropout).
July 2003 5 MIC37500/37501/37502
MIC37500/37501/37502 Micrel
Typical Characteristics
0
50
100
150
200
250
300
350
400
450
012345
DROPOUT (mV)
OUTPUT CURRENT (A)
Dropout
vs. Output Current
2.5VOUT
250
300
350
400
450
500
-40 -20 0 20 40 60 80 100120
DROPOUT (mV)
TEMPERATURE (°C)
Dropout
vs. Temperature
2.5VOUT
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.5 1.7 1.9 2.1 2.3 2.5
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Dropout Characteristics
(1.5V)
10mA load
5A load
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
1.5 1.7 1.9 2.1 2.3 2.5 2.7
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Dropout Characteristics
(1.8V)
5A load
10mA load
0
0.5
1.0
1.5
2.0
2.5
3.0
1.5 2.0 2.5 3.0 3.5
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Dropout Characteristics
(2.5V)
5A load
10mA load
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
1.5
1.8
2.0
2.3
2.5
2.8
3.0
3.3
3.5
3.8
4.0
4.3
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Dropout Characteristics
(3.3V)
10mA load
5A load
0
5
10
15
20
25
30
35
40
45
50
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
GROUND CURRENT (mA)
OUTPUT CURRENT (A)
Ground Current
vs. Output Current
2.5VOUT
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
012345
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
Ground Current
vs. Suppl
y
Volta
g
e (1.5V)
10mA
100mA
0
10
20
30
40
50
60
70
80
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
Ground Current
vs. Supply (1.5V)
2.5A
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
012345
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
Ground Current
vs. Supply (1.8V)
10mA
100mA
0
10
20
30
40
50
60
70
80
90
012345
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
Ground Current
vs. Suppl
y
(1.8V)
2.5A
5A
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
012345
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
Ground Current
vs. Supply (2.5V)
10mA
100mA
MIC37500/37501/37502 Micrel
MIC37500/37501/37502 6 July 2003
0
0.02
0.04
0.06
0.08
0.10
0.12
012345
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
Ground Current
vs. Suppl
y
(2.5V)
2.5A
5A
0
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
012345
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
Ground Current
vs. Suppl
y
(3.3V)
100mA
10mA
0
20
40
60
80
100
120
012345
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
Ground Current
vs. Suppl
y
(3.3V)
2.5A
5A
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-40 -20 0 20 40 60 80 100120
GROUND CURRENT (mA)
TEMPERATURE (°C)
Ground Current
vs. Temperature
100mA
10mA
0
10
20
30
40
50
60
-40 -20 0 20 40 60 80 100120
GROUND CURRENT (mA)
TEMPERATURE (°C)
Ground Current
vs. Temperature
2.5A
1A
5A
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 100120
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
Output Voltage
vs. Temperature
0
1
2
3
4
5
6
7
8
9
10
2.25 3 3.75 4.5 5.25 6
SHORT CIRCUIT CURRENT (A)
SUPPLY VOLTAGE (V)
Short Circuit Current
vs. Suppl
y
Volta
g
e
0
1
2
3
4
5
6
7
8
9
10
-40 -20 0 20 40 60 80 100120
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
Short Circuit Current
vs. Temperature
0
1
2
3
4
5
6
0.01 0.1 1 10 100 100010000
ERROR FLAG (V)
RESISTANCE (kΩ)
Error Fla
g
Pull-Up Resistor
VIN = 5V
Flag High (OK)
Flag Low (FAULT)
0
2
4
6
8
10
12
-40 -20 0 20 40 60 80 100120
ENABLE CURRENT (µA)
TEMPERATURE (°C)
Enable Current
vs. Temperature
July 2003 7 MIC37500/37501/37502
MIC37500/37501/37502 Micrel
Functional Characteristics
TIME (20µs/div.)
ENABLE
(1V/div.) OUTPUT VOLTAGE
(1V/div.)
VIN = 3.3V
VOUT = 2.5V
COUT = 100µF Ceramic
IOUT = 5A
Enable T ransient Response
TIME (100µs/div.)
INPUT V OLTAGE
(2V/div.) OUTPUT VOLTAGE
(20mV/div.)
VIN = 3.3V
VOUT = 2.5V
COUT = 100µF Ceramic
Line T ransient Response
3.3V
5V
TIME (100µs/div.)
LOAD TRANSIENT
(2A/div.) OUTPUT VOLTAGE
(100mV/div.)
VIN = 3.3V
VOUT = 2.5V
COUT = 100µF Ceramic
Load T ransient Response
1A
5A
TIME (100µs/div.)
LOAD TRANSIENT
(2A/div.) OUTPUT VOLTAGE
(100mV/div.)
VIN = 3.3V
VOUT = 2.5V
COUT = 100µF Ceramic
Load T ransient Response
100mA
5A
MIC37500/37501/37502 Micrel
MIC37500/37501/37502 8 July 2003
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-emitter voltage
drop and collector-to-emitter saturation voltage, dropout per-
formance of the PNP output of these devices is limited only
by the low VCE saturation voltage.
A trade-off for the low dropout voltage is a varying base drive
requirement. Micrel’s Super Beta PNP™ 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. 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 (TA)
•Output current (IOUT)
•Output voltage (VOUT)
•Input voltage (VIN)
•Ground current (IGND)
First, calculate the power dissipation of the regulator from
these numbers and the device parameters from this datasheet.
PD = (VIN – VOUT) IOUT + VIN IGND
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:
θSA = ((TJ(MAX) – TA)/ PD) – (θJC + θCS)
Where TJ(MAX) ≤ 125°C and θCS 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 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 1.0µF 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 µCap LDO, the MIC37500/01/02 can operate
with ceramic output capacitors as long as the amount of
capacitance is 100µF or greater. For values of output capaci-
tance lower than 100µF, the recommended ESR range is
200mΩ to 2Ω. The minimum value of output capacitance
recommended for the MIC37500/01/02 is 47µF.
For 100µF or greater the ESR range recommended is less
than 1Ω. Ultra-low ESR, ceramic capacitors are recom-
mended for output capacitance of 100µF or greater to help
improve transient response and noise reduction at high
frequency. X7R/X5R dielectric-type ceramic capacitors are
recommended because of their temperature performance.
X7R-type capacitors change capacitance by 15% over their
operating 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.
Input Capacitor
An input capacitor of 1.0µF or greater is recommended when
the device is more than 4 inches away from the bulk 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 47µF 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.
July 2003 9 MIC37500/37501/37502
MIC37500/37501/37502 Micrel
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 microamperes of leakage). The enable input is TTL/
CMOS compatible for simple logic interface, but can be
connected to up to VIN. When enabled, it draws approxi-
mately 15µA.
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 1MΩ, 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 VOUT 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).
MIC37500/37501/37502 Micrel
MIC37500/37501/37502 10 July 2003
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)
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)
July 2003 11 MIC37500/37501/37502
MIC37500/37501/37502 Micrel
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.
0.067±0.005 0.032 ±0.003
0.360±0.005
0.600±0.025
0.405±0.005
0.060±0.005
0.176±0.005
8° MAX 0.100±0.01
0.050±0.005
0.015 ±0.002
0.004+0.004
–0.008
SEATING PLANE
0.065±0.010
20°±2°
DIM. = INCH
5-Lead TO-263 (U)