June 1999
1
MIC39500/39501
MIC39500/39501
Micrel
Ordering Information
Part Number
Voltage
Junction Temp. Range
Package
MIC39500-2.5BT
2.5V
40
C to +125
C
3-lead TO-220
MIC39500-2.5BU
2.5V
40
C to +125
C
3-lead TO-263
MIC39501-2.5BT
2.5V
40
C to +125
C
5-lead TO-220
MIC39501-2.5BU
2.5V
40
C to +125
C
5-lead TO-263
MIC39500/39501
5A Low-Voltage Low-Dropout Regulator
Advance Information
General Description
The MIC39500 and MIC39501 is a 5A low-dropout linear
voltage regulator that provides a low-voltage, high-current
output with a minimum of external components. Utilizing
Micrel's proprietary Super
eta PNPTM pass element, the
MIC39500 offers extremely low dropout (typically 400mV at
5A) and low ground current (typically 70mA at 5A).
The MIC39500 is ideal for PC Add-In cards that need to
convert from standard 5V or 3.3V, down to new, lower core
voltages. A guaranteed maximum dropout voltage of 500mV
over all operating conditions allows the MIC39500 to provide
2.5V from a supply as low as 3V. The MIC39500 also has fast
transient response, for heavy switching applications. The
device requires only 47
F of output capacitance to maintain
stability and achieve fast transient response
The MIC39500 is fully protected with overcurrent limiting,
thermal shutdown, reversed-battery and reversed-lead in-
sertion protection. The MIC39501 offers a TTL-logic-compat-
ible enable pin and an error flag that indicates undervoltage
and overcurrent conditions. The MIC39500 comes in the TO-
220 and TO-263 packages and is an ideal upgrade to older,
NPN-based linear voltage regulators.
For applications requiring input voltage
greater than 16V, see the
MIC29500/1/2/3 family.
Typical Application
IN
OUT
GND
V
IN
3.3V
V
OUT
2.5V
1.0F
47F
MIC39500-2.5
MIC39500
Features
5A minimum guaranteed output current
500mV maximum dropout voltage over temperature
1% initial accuracy
Low ground current
Current limiting and thermal shutdown
Reversed-battery and reversed-lead insertion protection
Fast transient response
TO-263 and TO-220 packages
TTL/CMOS compatible enable pin (MIC39501 only)
Error flag output (MIC39501 only)
Applications
LDO linear regulator for PC add-in cards
PowerPCTM power supplies
High-efficiency linear power supplies
SMPS post regulator
Multimedia and PC processor supplies
Low-voltage microcontrollers
StrongARMTM processor supply
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
StrongARM is a trademark of Advanced RISC Machines, Ltd.
MIC39501-2.5
FLG
OUT
ERROR
FLAG OUTPUT
47F
EN
GND
IN
V
OUT
2.5V
1.0F
Enable
Shutdown
V
IN
3.3V
100K
MIC39501
MIC39500/39501
Micrel
MIC39500/39501
2
June 1999
Pin Description
Pin Number
Pin Number
Pin Name
Pin Function
MIC39500
MIC39501
1
EN
Enable (Input): TTL/CMOS compatible input. Logic high = enable; logic low
or open = shutdown
1
2
IN
Unregulated Input: +16V maximum supply.
2,
TAB
3,
TAB
GND
Ground: Ground pin and
TAB
are internally connected.
3
4
OUT
Regulator Output
5
FLG
Error Flag (Ouput): Open collector output. Active low indicates an output
fault condition.
Pin Configuration
TAB
3
OUT
2
GND
1
IN
MIC39500-x.xBT
TO-220 (T)
TAB
5
FLG
4
OUT
3
GND
2
IN
1
EN
MIC39501-x.xBT
TO-220-5 (T)
TAB
3
OUT
2
GND
1
IN
MIC39500-x.xBU
TO-263 (U)
TAB
5
FLG
4
OUT
3
GND
2
IN
1
EN
MIC39501-x.xBU
TO-263-5 (U)
June 1999
3
MIC39500/39501
MIC39500/39501
Micrel
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
IN
) ..................................... 20V to +20V
Enable Voltage (V
EN
) .................................................. +20V
Storage Temperature (T
S
) ....................... 65
C to +150
C
Lead Temperature (soldering, 5 sec.) ....................... 260
C
ESD, Note 3
Operating Ratings
(Note 2)
Supply Voltage (V
IN
) .................................. +2.25V to +16V
Enable Voltage (V
EN
) .................................................. +16V
Maximum Power Dissipation (P
D(max)
) ..................... Note 4
Junction Temperature (T
J
) ....................... 40
C to +125
C
Package Thermal Resistance
TO-263
(
JC
) ......................................................... 2
C/W
TO-220 (
JC
) ......................................................... 2
C/W
Electrical Characteristics
T
J
= 25
C, bold values indicate 40
C
T
J
+125
C; unless noted
Symbol
Parameter
Condition
Min
Typ
Max
Units
V
OUT
Output Voltage
10mA
I
OUT
5A, V
OUT
+ 1V
V
IN
16V
1
1
%
2
2
%
Line Regulation
I
OUT
= 10mA, V
OUT
+ 1V
V
IN
16V
0.06
0.5
%
Load Regulation
V
IN
= V
OUT
+ 1V, 10mA
I
OUT
5A
0.2
1
%
V
OUT
/
T
Output Voltage Temp. Coefficient,
20
100
ppm/
C
Note 5
V
DO
Dropout Voltage, Note 6
I
OUT
= 250mA,
V
OUT
= 2%
125
250
mV
I
OUT
= 2.5A,
V
OUT
= 2%
320
mV
I
OUT
= 5A,
V
OUT
= 2%
400
500
mV
I
GND
Ground Current, Note 7
I
OUT
= 2.5A, V
IN
= V
OUT
+ 1V
15
50
mA
I
OUT
= 5A, V
IN
= V
OUT
+ 1V
70
mA
I
GND(do)
Dropout Ground Pin Current
V
IN
V
OUT(nominal)
0.5V, I
OUT
= 10mA
2.1
mA
I
OUT(lim)
Current Limit
V
OUT
= 0V, V
IN
= V
OUT
+ 1V
7.5
A
e
n
Output Noise Voltage
C
OUT
= 47
F, I
OUT
= 100mA, 10Hz to 100kHz
260
V(rms)
Enable Input (MIC39501)
V
EN
Enable Input Voltage
logic low (off)
0.8
V
logic high (on)
2.4
V
I
IN
Enable Input Current
V
EN
= V
IN
30
35
A
75
A
V
EN
= 0.8V
2
A
4
A
I
OUT(shdn)
Shutdown Output Current
Note 8
10
20
A
Flag Output (MIC39501)
I
FLG(leak)
Output Leakage Current
V
OH
= 16V
0.01
1
A
2
A
V
FLG(do)
Output Low Voltage
V
IN
= 2.250V, I
OL
, = 250
A, Note 9
125
150
mV
200
mV
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.
Devices are ESD sensitive. Handling precautions recommended.
Note 4.
P
D(max)
= (T
J(max)
T
A
)
JA
, where
JA
depends upon the printed circuit layout. See "Applications Information."
Note 5.
Output voltage temperature coefficient is
V
OUT(worst case)
(T
J(max)
T
J(min)
) where T
J(max)
is +125
C and T
J(min)
is 0
C.
Note 6.
V
DO
= V
IN
V
OUT
when V
OUT
decreases to 98% of its nominal output voltage with V
IN
= V
OUT
+ 1V.
Note 7.
I
GND
is the quiescent current. I
IN
= I
GND
+ I
OUT
.
Note 8.
V
EN
0.8V, V
IN
8V, and V
OUT
= 0V
Note 9.
For a 2.5V device, V
IN
= 2.250V (device is in dropout).
MIC39500/39501
Micrel
MIC39500/39501
4
June 1999
Functional Diagram
Ref.
18V
O.V.
I
LIMIT
Thermal
Shut-
down
1.240V
1.180V
EN*
IN
FLAG*
GND
OUT
* MIC39501 only
June 1999
5
MIC39500/39501
MIC39500/39501
Micrel
Applications Information
The MIC39500/1 is a high-performance low-dropout voltage
regulator suitable for moderate to high-current voltage regu-
lator applications. Its 500mV dropout voltage at full load
makes it especially valuable in battery-powered systems and
as a high-efficiency noise filter in post-regulator applications.
Unlike older NPN-pass transistor designs, where the mini-
mum dropout voltage is limited by the base-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 V
CE
saturation voltage.
A trade-off for the low dropout voltage is a varying base drive
requirement. Micrel's Super
eta PNPTM process reduces
this drive requirement to only 2% to 5% of the load current.
The MIC39500/1 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 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.
MIC39500-x.x
IN
OUT
GND
C
IN
C
OUT
V
IN
V
OUT
Figure 1. Capacitor Requirements
Thermal Design
Linear regulators are simple to use. The most complicated
design parameters to consider are thermal characteristics.
Thermal design requires four application-specific param-
eters:
Maximum ambient temperature (T
A
)
Output Current (I
OUT
)
Output Voltage (V
OUT
)
Input Voltage (V
IN
)
Ground Current (I
GND
)
Calculate the power dissipation of the regulator from these
numbers and the device parameters from this datasheet,
where the ground current is taken from data sheet.
P
D
= (V
IN
V
OUT
)
I
OUT
+ V
IN
I
GND
The heat sink thermal resistance is determined by:
SA
J(max)
A
D
JC
CS
T
T
P
=
-
-
+
(
)
where:
T
J (max)
125
C and
CS
is between 0
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
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 specification.
Output capacitor
The MIC39500/1 requires an output capacitor to maintain
stability and improve transient response. Proper capacitor
selection is important to ensure proper operation. The
MIC39500/1 output capacitor selection is dependent upon
the ESR (equivalent series resistance) of the output capacitor
to maintain stability. When the output capacitor is 47
F or
greater, the output capacitor should have less than 1
of
ESR. This will improve transient response as well as promote
stability. Ultra-low-ESR capacitors, such as ceramic chip
capacitors may promote instability. These very low ESR
levels may cause an oscillation and/or underdamped tran-
sient response. A low-ESR solid tantalum capacitor works
extremely well and provides good transient response and
stability over temperature. Aluminum electrolytics can also
be used, as long as the ESR of the capacitor is < 1
.
The value of the output capacitor can be increased without
limit. Higher capacitance values help to improve transient
response and ripple rejection and reduce output noise.
Input capacitor
An input capacitor of 1
F or greater is recommended when
the device is more than 4 inches away from the bulk ac supply
capacitance, or when the supply is a battery. Small surface-
mount ceramic chip capacitors can be used for bypassing.
Larger values will help to improve ripple rejection by bypass-
ing the input to the regulator, further improving the integrity of
the output voltage.
Transient Response
The MIC39500/1 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, preferably tantalum, is all that is required. Larger
values improve performance even further.
3.3V to 2.5V Conversion
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, 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
MIC39500/1 regulator provides excellent performance with
MIC39500/39501
Micrel
MIC39500/39501
6
June 1999
an input as low as 3.0V. This gives PNP-based regulators a
distinct advantage over older, NPN-based linear regulators.
A typical NPN regulator does not have the headroom to do
this conversion.
Minimum Load Current
The MIC39500/1 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 regulation.
Error Flag
The MIC39501 version features an error flag circuit which
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 MIC39501 version features 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 20V.
June 1999
7
MIC39500/39501
MIC39500/39501
Micrel
Package Information
0.018
0.008
(0.46
0.020)
0.100
0.005
(2.54
0.13)
0.030
0.003
(0.76
0.08)
0.050
0.003
(1.27
.08)
7
1.140
0.010
(28.96
0.25)
0.356
0.005
(9.04
0.13)
0.590
0.005
(14.99
0.13)
0.108
0.005
(2.74
0.13)
0.050
0.005
(1.27
0.13)
0.151 D
0.005
(3.84 D
0.13)
0.410
0.010
(10.41
0.25)
0.176
0.005
(4.47
0.13)
0.100
0.020
(2.54
0.51)
0.818
0.005
(20.78
0.13)
7
3
DIMENSIONS: INCH
(MM)
TO-220 (T)
0.018
0.008
(0.46
0.20)
0.268 REF
(6.81 REF)
0.032
0.005
(0.81
0.13)
0.550
0.010
(13.97
0.25)
7
Typ.
SEATING
PLANE
0.578
0.018
(14.68
0.46)
0.108
0.005
(2.74
0.13)
0.050
0.005
(1.27
0.13)
0.150 D
0.005
(3.81 D
0.13)
0.400
0.015
(10.16
0.38)
0.177
0.008
(4.50
0.20)
0.103
0.013
(2.62
0.33)
0.241
0.017
(6.12
0.43)
0.067
0.005
(1.70
0.127)
inch
(mm)
Dimensions:
TO-220-5 (T)
MIC39500/39501
Micrel
MIC39500/39501
8
June 1999
0.360
0.005
0.600
0.025
0.405
0.005
0.100 BSC
0.050
0.050
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
TO-263 (U)
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
TO-263-5 (U)
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.
1999 Micrel Incorporated
PDF 
ZIP