March 2001
1
MIC29710/29712
MIC29710/29712
Micrel
Ordering Information
Part Number
Temp. Range*
Voltage
Current
Package
MIC29710-3.3BT
0
C to +125
C
3.3V
7.5A
TO-220-3
MIC29710-5.0BT
0
C to +125
C
5.0V
7.5A
TO-220-3
MIC29712BT
0
C to +125
C
Adj.
7.5A
TO-220-5
* Junction Temperature
General Description
The MIC29710 and MIC29712 are high-current, high-accu-
racy, low-dropout voltage regulators featuring fast transient
recovery from input voltage surges and output load current
changes. These regulators use a PNP pass element that
features Micrel's proprietary Super eta PNPTM process.
The MIC29710/2 is available in two versions: the three pin
fixed output MIC29710 and the five pin adjustable output
voltage MIC29712. All versions are fully protected against
overcurrent faults, reversed lead insertion, overtemperature
operation, and positive and negative transient voltage spikes.
A TTL compatible enable (EN) control pin supports external
on/off control. If on/off control is not required, the device may
be continuously enabled by connecting EN to IN.
The MIC29710/2 is available in the standard three and five
pin TO-220 package with an operating junction temperature
range of 0
C to +125
C. The MIC29710 is also available in the
5-lead TO-263 package.
For applications requiring even lower dropout voltage or input
voltage greater than 16V, see the MIC29750/29752.
Features
Fast transient response
7.5A current capability
700mV dropout voltage at full load
Low ground current
Accurate 2% guaranteed tolerance
"Zero" current shutdown mode (MIC29712)
Fixed voltage and adjustable versions
Applications
PentiumTM, Pentium PlusTM, and Power PCTM
processor supplies
High-efficiency "green" computer systems
High-efficiency linear power supplies
High-efficiency switching supply post regulator
Battery-powered equipment
MIC29710/29712
7.5A Fast-Response LDO Regulator
Final Information
Fixed Regulator Configuration
Adjustable Regulator Configuration
Typical Application
MIC29712
OUT
ADJ
R1
V
OUT
R2
EN
GND
V
IN
IN
On
Off
V
OUT
= 1.240
R1
R2
1
MIC29710
OUT
V
OUT
IN
GND
V
IN
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
MIC29710/29712
Micrel
MIC29710/29712
2
March 2001
Pin Description
3-Pin TO-220 (MIC29710)
Pin Number
Pin Name
Pin Function
1
IN
Unregulated Input: +16V maximum supply.
2
GND
Ground: Internally connected to tab (ground).
3
OUT
Regulated Output
5-Pin TO-220 (MIC29712)
Pin Number
Pin Name
Pin Function
1
EN
Enable (Input): Logic-level ON/OFF control.
2
IN
Unregulated Input: +16V maximum supply.
3
GND
Ground: Internally connected to tab (ground).
4
OUT
Regulated Output
5
ADJ
Output Voltage Adjust: 1.240V feedback from external resistive divider.
Operating Ratings
Operating Junction Temperature ................. 0
C to +125
C
JC
(TO-220) ............................................................. 2
C/W
JA
(TO-220) ........................................................... 55
C/W
Absolute Maximum Ratings
Input Supply Voltage, Note 1 ...................... 0.7 V to +20V
Power Dissipation .................................... Internally Limited
Storage Temperature Range ................... 65
C to +150
C
Lead Temperature (Soldering, 5 sec.) ...................... 260
C
Pin Configuration
MIC29712BT
1 2 3
MIC29710BT
On all devices, the Tab is grounded.
1 2 3 4 5
March 2001
3
MIC29710/29712
MIC29710/29712
Micrel
Reference (MIC29712 only)
Reference Voltage
10mA
I
O
7.5A, V
OUT
+ 1V
V
IN
8V, Note 2
1.215
1.240
1.265
V
MAX
Adjust Pin Bias Current
40
80
nA
120
nA
Reference Voltage
Note 7
20
ppm/
C
Temperature Coefficient
Adjust Pin Bias Current
0.1
nA/
C
Temperature Coefficient
Electrical Characteristics
(Note 9)
All measurements at T
J
= 25
C unless otherwise noted. Bold values are guaranteed across the operating temperature range.
Parameter
Condition
Min
Typ
Max
Units
Output Voltage
10mA
I
O
7.5A, (V
OUT
+ 1V)
V
IN
8V, Note 2
2
2
%
Line Regulation
I
O
= 10mA, (V
OUT
+ 1V)
V
IN
8V
0.06
0.5
%
Load Regulation
V
IN
= V
OUT
+ 1V, 10mA
I
OUT
7.5A, Notes 2, 6
0.2
1
%
Output Voltage
V
O
/
T, Note 6
20
100
ppm/
C
Temperature Coefficient
Dropout Voltage
V
OUT
= 1%, (Note 3)
MIC29710/29712
I
O
= 100mA
80
200
mV
I
O
= 750mA
180
mV
I
O
= 1.5A
220
mV
I
O
= 3A
300
mV
I
O
= 5A
450
mV
I
O
= 7.5A
700
1000
mV
Ground Current
MIC29710/29712
I
O
= 750mA, V
IN
= V
OUT
+ 1V
6
20
mA
I
O
= 1.5A
20
mA
I
O
= 3A
36
mA
I
O
= 5A
100
mA
I
O
= 7.5A
250
375
mA
I
GNDDO
Ground Pin
V
IN
= 0.5V less than specified V
OUT
. I
OUT
= 10mA
1
2
mA
Current at Dropout
Current Limit
MIC29710/29712 V
OUT
= 0V, Note 4
11
15
A
e
n
, Output Noise Voltage
C
L
= 47
F
I
o
= 100mA
260
V
RMS
(10Hz to 100kHz)
V
OUT
= 5.0V
MIC29710/29712
Micrel
MIC29710/29712
4
March 2001
On/Off
Reference
Bias
Feed-
back
GND
28V
OUT
ADJ
EN
IN
O.V.
I
LIMIT
Thermal
Shut-
down
Block Diagram
Enable Input (MIC29712 only)
Input Logic Voltage
Low (Off)
0.8
V
High (On)
2.4
V
Enable (EN) Pin Input Current
V
EN
= V
IN
15
30
A
75
A
V
EN
= 0.8V
2
A
4
A
Regulator Output
(Note 8)
10
A
Current in Shutdown
20
A
General Note: Devices are ESD sensitive. Handling precautions are recommended.
Note 1:
The maximum continuous supply voltage is 16V.
Note 2:
For testing, MIC29712 V
OUT
is programmed to 5V.
Note 3:
Dropout voltage is defined as the input-to-output differential when the output voltage drops to 99% of its nominal value with V
OUT
+ 1V applied
to V
IN
.
Note 4:
For this test, V
IN
is the larger of 8V or V
OUT
+ 3V.
Note 5:
Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground
pin current.
Note 6:
Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 7:
V
REF
V
OUT
(V
IN
1 V), 2.4V
V
IN
8V, 10mA < I
L
7.5A, T
J
T
J MAX.
Note 8: V
EN
0.8V and V
IN
16V, V
OUT
= 0.
Note 9:
Specification for packaged product only.
Parameter
Conditions
Min
Typical
Max
Units
16V
March 2001
5
MIC29710/29712
MIC29710/29712
Micrel
0
0.1
0.2
0.3
0.4
0.5
0.6
0
2
4
6
8
DROPOUT VOLTAGE (V)
OUTPUT CURRENT (A)
MIC29710/2 Dropout Voltage
vs. Output Current
0
0.2
0.4
0.6
0.8
1.0
-60 -30
0
30
60
90 120 150
DROPOUT VOLTAGE (V)
TEMPERATURE (
C)
MIC29710/2 Dropout Voltage
vs. Temperature
I
LOAD
= 7.5A
0
1
2
3
4
0
4
8
12
16
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
MIC29710-3.3
Dropout Characteristics
I
LOAD
= 7.5A
I
LOAD
= 10mA
Typical Characteristics
0A
3.525V
+50mV
50mV
LOAD CURRENT OUTPUT VOLTAGE
MIC29712 Load Transient Response
(See Test Circuit Schematic)
1ms/division
2A
200mA
4A
6A
8A
6.525V
4.525V
3.525V
+20mV
20mV
OUTPUT VOLTAGE INPUT VOLTAGE
MIC29712 Line Transient Response
with 10mA Load, 10
F Output Capacitance
200
s/division
I
OUT
= 10mA
C
OUT
=10
F
6.525V
4.525V
3.525V
+20mV
20mV
OUTPUT VOLTAGE INPUT VOLTAGE
MIC29712 Line Transient Response
with 10mA Load, 100
F Output Capacitance
200
s/division
I
OUT
= 10mA
C
OUT
= 100
F
V
IN
= V
OUT
+ 1V
MIC29712
EN
IN
OUT
ADJ
GND
0.1F
93.1k
1%
49.9k
1%
V
OUT
3.525V nominal
6
330F
AVX
TPSE337M006R0100
tantalum
V
OUT
load (not shown): Intel Power Validator
MIC29712 Load Transient Response Test Circuit
MIC29710/29712
Micrel
MIC29710/29712
6
March 2001
0
2
4
6
8
10
0
2
4
6
8
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
MIC29710/2 Ground Current
vs. Input Voltage
I
OUT
= 10mA
0
50
100
150
200
250
300
350
0
2
4
6
8
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
MIC29710/2 Ground Current
vs. Input Voltage
I
OUT
= 7.5A
0
2
4
6
8
10
12
-60 -30
0
30
60
90 120 150
GROUND CURRENT (mA)
TEMPERATURE (
C)
MIC29710/2 Ground Current
vs. Temperature
I
OUT
= 750mA
V
IN
= V
OUT
+ 1
0
10
20
30
40
50
-60 -30
0
30
60
90 120 150
GROUND CURRENT (mA)
TEMPERATURE (
C)
MIC29710/2 Ground Current
vs. Temperature
I
OUT
= 3.75A
V
IN
= V
OUT
+ 1
0
50
100
150
200
250
300
350
-100
-50
0
50
100
150
GROUND CURRENT (mA)
TEMPERATURE (
C)
MIC29710/2 Ground Current
vs. Temperature
I
OUT
= 7.5A
V
IN
= V
OUT
+ 1
0
50
100
150
200
250
0
2
4
6
8
GROUND CURRENT (mA)
OUTPUT CURRENT (A)
MIC29710/2 Ground Current
vs. Output Current
V
IN
= V
OUT
+ 1
3.20
3.22
3.24
3.26
3.28
3.30
3.32
3.34
3.36
3.38
3.40
-60 -30
0
30
60
90 120 150
OUTPUT VOLTAGE (V)
TEMPERATURE (
C)
MIC29710-3.3 Output Voltage
vs. Temperature
3 DEVICES
0
2
4
6
8
10
12
-60 -30
0
30
60
90 120 150
CURRENT (A)
TEMPERATURE (
C)
MIC29710/2 Short Circuit
Current vs. Temperature
V
OUT
= 0V
0
5
10
15
20
25
30
35
40
-60 -30
0
30
60
90 120 150
ENABLE CURRENT (
A)
TEMPERATURE (
C)
MIC29712 Enable Current
vs. Temperaure
V
EN
= 5V
V
EN
= 2V
0
10
20
30
40
50
-60 -30
0
30
60
90 120 150
ADJUST PIN CURRENT (nA)
TEMPERATURE (
C)
MIC29712 Adjust Pin Current
vs. Temperature
0.001
0.01
0.1
1
10
10x10
0
100x10
0
1x10
3
10x10
3
100x10
3
1x10
6
OUTPUT IMPEDANCE (
)
FREQUENCY (Hz)
MIC29710/2 Output Impedance
vs. Frequency
March 2001
7
MIC29710/29712
MIC29710/29712
Micrel
Applications Information
The MIC29710 and MIC29712 are high performance low-
dropout voltage regulators suitable for all moderate to high-
current voltage regulator applications. Their 700mV of drop-
out voltage at full load make them especially valuable in
battery powered systems and as high efficiency noise filters
in "post-regulator" applications. Unlike older NPN-pass tran-
sistor designs, where the minimum dropout voltage is limited
by the base-emitter voltage drop and collector-emitter satu-
ration voltage, dropout performance of the PNP output of
these devices is limited merely by the low V
CE
saturation
voltage. Output regulation is excellent across the input volt-
age, output current, and temperature ranges.
A trade-off for the low dropout voltage is a varying base drive
requirement. But Micrel's Super eta PNPTM process re-
duces this drive requirement to merely 2 to 5% of the load
current.
MIC29710/712 regulators are fully protected from damage
due to fault conditions. Current limiting is provided. The
output current under overload conditions is limited to a
constant value. Thermal shutdown disables the device when
the die temperature exceeds the maximum safe operating
temperature. Transient protection allows device (and load)
survival even when the input voltage spike above and below
nominal. The MIC29712 version offers a logic level ON/OFF
control: when disabled, the devices draw nearly zero current.
An additional feature of this regulator family is a common
pinout: a design's current requirement may change up or
down yet use the same board layout, as all of Micrel's high-
current Super eta PNPTM regulators have identical pinouts.
IN
OUT
GND
V
IN
V
OUT
Figure 3. The MIC29710 requires only two capacitors
for operation.
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
First, we calculate the power dissipation of the regulator from
these numbers and the device parameters from this datasheet.
P
D
= I
OUT
(1.03V
IN
V
OUT
)
Where the ground current is approximated by 3% of I
OUT
.
Then the heat sink thermal resistance is determined with this
formula:
T
J MAX
T
A
SA
= ------------ (
JC
+
CS
)
P
D
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 very
significant reductions in regulator power dissipation and the
associated heat sink without compromising performance.
When this technique is employed, a capacitor of at least
0.1
F is needed directly between the input and regulator
ground.
Please refer to Application Note 9 for further details and
examples on thermal design and heat sink specification.
Capacitor Requirements
For stability and minimum output noise, a capacitor on the
regulator output is necessary. The value of this capacitor is
dependent upon the output current; lower currents allow
smaller capacitors. MIC29710/2 regulators are stable with a
minimum capacitor value of 47
F at full load.
This capacitor need not be an expensive low ESR type:
aluminum electrolytics are adequate. In fact, extremely low
ESR capacitors may contribute to instability. Tantalum ca-
pacitors are recommended for systems where fast load
transient response is important.
Where the regulator is powered from a source with a high AC
impedance, a 0.1
F capacitor connected between Input and
GND is recommended. This capacitor should have good
characteristics to above 250kHz.
Transient Response and 5V to 3.3V Conversion
The MIC29710/2 have excellent response to variations in
input voltage and load current. By virtue of their low dropout
voltage, these devices do not saturate into dropout as readily
as similar NPN-based designs. A 3.3V output Micrel LDO will
maintain full speed and performance with an input supply as
low as 4.2V, and will still provide some regulation with
supplies down to 3.8V, unlike NPN devices that require 5.1V
or more for good performance and become nothing more
than a resistor under 4.6V of input. Micrel's PNP regulators
provide superior performance in "5V to 3.3V" conversion
applications, especially when all tolerances are considered.
MIC29710/29712
Micrel
MIC29710/29712
8
March 2001
Adjustable Regulator Design
The adjustable regulator version, MIC29712, allows pro-
gramming the output voltage anywhere between 1.25V and
the 16V maximum operating rating of the family. Two resis-
tors are used. Resistors can be quite large, up to 100k
,
because of the very high input impedance and low bias
current of the sense comparator. The resistor values are
calculated by:
V
OUT
R1 = R2
( ------ 1)
1.240
Where V
O
is the desired output voltage. Figure 4 shows
component definition.
R1
100k
R2
56.2k
VOUT = 1.240V
[1 + (R1 / R2)]
VIN
4.75 to 5.25
VOUT
3.45V
MIC29712BT
33F
10F
Figure 4. Adjustable Regulator with Resistors
Enable Input
The MIC29712 versions features an enable (EN) input that
allows ON/OFF control of the device. Special design allows
"zero" current drain when the device is disabled--only micro-
amperes of leakage current flows. The EN input has TTL/
CMOS compatible thresholds for simple interfacing with
logic, or may be directly tied to V
IN
. Enabling the regulator
requires approximately 20
A of current into the EN pin.
Minimum Load Current
The MIC29710/12 regulators are specified between finite
loads. If the output current is to small, leakage currents
dominate and the output voltage rises. A 10mA minimum load
current is necessary for proper regulation.
Voltage
Standard (
)
R1
R2
2.85
100k
76.8k
2.9
100k
75.0k
3.0
100k
69.8k
3.1
100k
66.5k
3.15
100k
64.9k
3.3
100k
60.4k
3.45
100k
56.2k
3.525
93.1k
51.1k
3.6
100k
52.3k
3.8
100k
48.7k
4.0
100k
45.3k
4.1
100k
43.2k
Figure 5. MIC29712 Resistor Table
March 2001
9
MIC29710/29712
MIC29710/29712
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)
3-Lead 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:
5-Lead TO-220 (T)
MIC29710/29712
Micrel
MIC29710/29712
10
March 2001
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)
March 2001
11
MIC29710/29712
MIC29710/29712
Micrel
MIC29710/29712
Micrel
MIC29710/29712
12
March 2001
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.
March 2001 Micrel Incorporated
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