MIC29710/29712
7.5A Fast-Response LDO Regulator
Super ßeta PNP is a registered trademark of Micrel, Inc. Pentium is a registered trademark of Intel Corporation.
PowerPC is a registered trademark of IBM Corporation.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
October 2006 1 M9999-101906
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 ßeta PNP
®
process.
The MIC29710 is available in the 3-pin fixed output and
the MIC29712 is available in the 5-pin adjustable output
voltage. Both versions are fully protected against
overcurrent faults, reversed lead insertion, over-
temperature 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 maybe continuously enabled by connecting EN to
IN.
The MIC29710 is available in the standard 3-pin TO-220
package the MIC29712 is available in the 5-pin TO-220
package with an operating junction temperature range of
0°C to +125°C.
For applications requiring even lower dropout voltage or
input voltage greater than 16V, see the MIC297 50/29752.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
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
• Pentium
®
, Pentium
®
Plus, and Power PC
®
processor
supplies
• High-efficiency “green” computer systems
• High-efficiency linear power supplies
• High-efficiency switching supply post regulator
• Battery-powered equipment
Typical Application
⎟
⎠
⎞
⎜
⎝
⎛+= 1
R2
R1
1.240V
OUT
Fixed Regulator Configuration
Adjustable Regulator Configuration
Micrel, Inc. MIC29710/29712
October 2006 2 M9999-101906
Ordering Information(1)
Part Number
Standard RoHS Compliant*
Voltage Junction
Temp. Range Package
MIC29710-3.3BT MIC29710-3.3WT 3.3V 0°C to +125°C 3-Pin TO-220
MIC29710-5.0BT MIC29710-5.0WT 5.0V 0°C to +125°C 3-Pin TO-220
MIC29712BT MIC29712WT Adj 0°C to +125°C 5-Pin TO-220
Note:
* RoHS Compliant with ‘high-melting solder’ exemption.
Pin Configuration
1 2 3
12345
MIC29710BT/WT
MIC29712BT/WT
On both devices, the Tab is grounded
Pin Description
Pin Number
3-Pin TO-220
Pin Number
5-Pin TO-220
Pin Name Pin Name
– 1 EN Enable (Input): Logic-level ON/OFF control.
1 2 IN Unregulated Input: +16V maximum supply.
2 3 GND Ground: Internally connected to tab (ground).
3 4 OUT Regulated Output
– 5 ADJ
Output Voltage Adjust: 1.240V feedback from external resistive
divider.
Micrel, Inc. MIC29710/29712
October 2006 3 M9999-101906
Absolute Maximum Ratings
Input Supply Voltage (V
IN
)
(1)
......................... –0.7V to +20V
Power Dissipation. ....................................Internally Limited
Lead Temperature (soldering, 5 sec.)........................ 260°C
Storage Temperature (T
s
) ........................... –65°C to 150°C
EDS Rating
(2)
Operating Ratings
Junction Temperature (T
J
) ............................ 0°C to +125°C
Thermal Resistance
TO-220 (θ
JC
) ........................................................2°C/W
TO-220 (θ
JA
) ......................................................55°C/W
Electrical Characteristics(3)
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 4 –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 4, 8 0.2 1 %
Output Voltage
Temperature Coefficient
∆V
O
/∆T, Note 8 20 100
ppm/°C
Dropout Voltage ∆V
OUT
= – 1%, Note 5
MIC29710/29712
I
O
= 100mA
I
O
= 750mA
I
O
= 1.5A
I
O
= 3A
I
O
= 5A
I
O
= 7.5A
80
180
220
300
450
700
200
1000
mV
mV
mV
mV
mV
mV
Ground Current MIC29710/29712 I
O
= 750mA, V
IN
= V
OUT
+ 1V
I
O
= 1.5A
I
O
= 3A
I
O
= 5A
I
O
= 7.5A
6
20
36
100
250
20
375
mA
mA
mA
mA
mA
I
GNDDO
Ground Pin
Current at Dropout
V
IN
= 0.5V less than specified V
OUT
. I
OUT
= 10mA 1 2 mA
Current Limit MIC29710/29712 V
OUT
= 0V, Note 6 11 15 A
e
n
, Output Noise Voltage
(10Hz to 10kHz)
V
OUT
= 5.0V
C
L
= 47µF I
O
= 100mA 260 µV
RMS
Reference (MIC29712 only)
Reference Voltage 10mA ≤ I
O
≤ 7.5A, V
OUT
+ 1V ≤ V
IN
≤ 8V, Note 4 1.215 1.240 1.265 V
MAX
Adjust Pin Bias Current 40 80
120
nA
nA
Reference Voltage
Temperature Coefficient
Note 9 20 ppm/°C
Adjust Pin Bias Current
Temperature Coefficient
0.1 nA/°C
Enable Input (MIC29712 only)
Input Logic Voltage Low (Off)
High (On)
2.4
0.8 V
V
V
EN
= V
IN
15
30
75
µA
µA
Enable (EN) Pin
Input Current
V
EN
= 0.8V – 2
4
µA
µA
Regulator Output
Current in Shutdown
Note 10 10
20
µA
µA
Micrel, Inc. MIC29710/29712
October 2006 4 M9999-101906
Notes:
1. The maximum continuous supply voltage is 16V.
2. Devices are ESD sensitive. Handling precautions are recommended.
3. Specification for packaged product only.
4. For testing, MIC29712 V
OUT
is programmed to 5V.
5. 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
.
6. For this test, V
IN
is the larger of 8V or V
OUT
+ 3V.
7. 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.
8. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
9. V
REF
≤ V
OUT
≤ (V
IN
– 1 V), 2.4V ≤ V
IN
≤ 8V, 10mA < I
L
≤ 7.5A, T
J
≤ T
J MAX
.
10. V
EN
≤ 0.8V and V
IN
≤ 16V, V
OUT
= 0.
Micrel, Inc. MIC29710/29712
October 2006 5 M9999-101906
Typical Characteristics
MIC29710 Load Transient Response Test Circuit
Micrel, Inc. MIC29710/29712
October 2006 6 M9999-101906
Micrel, Inc. MIC29710/29712
October 2006 7 M9999-101906
Functional Diagram
Micrel, Inc. MIC29710/29712
October 2006 8 M9999-101906
Application 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” applica-
tions. Unlike older NPN-pass transistor designs, where
the minimum dropout voltage is limited by the base-
emitter voltage drop and collector-emitter saturation
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
voltage, output current, and temperature ranges.
A trade-off for the low dropout voltage is a varying base
drive requirement. But Micrel’s Super ßeta PNP
®
process reduces 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 ßeta PNP
®
regulators have identical
pinouts.
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
IOUT. Then the heat sink thermal resistance is
determined with this formula:
()
CSJC
D
AJMAX
SA
θθ
P
TT
θ+−
−
=
Where T
JMAX
≤ 125°C and θ
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
ßeta 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 0.1µF 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 regula-
tors are stable with a minimum capacitor value of 47µF
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 capacitors 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 0.1µF 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.
Micrel, Inc. MIC29710/29712
October 2006 9
M9999-101906
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 resistors are used. Resistors can be quite large, up
to 100kΩ, because of the very high input impedance and
low bias current of the sense comparator. The resistor
values are calculated by:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−×= 1
1.240
V
R2R1
OUT
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
33µF
10µF
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 20µA 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.
Standard (Ω)
Voltage 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
Micrel, Inc. MIC29710/29712
October 2006 10
M9999-101906
Package Information
3-Pin TO-220 (T)
5-Pin TO-220 (T)
Micrel, Inc. MIC29710/29712
October 2006 11
M9999-101906
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet 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 a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2004 Micrel, Incorporated.
