MIC29712BT Micrel Inc, MIC29712BT Datasheet - Page 8

• Manufacturer Part Number: MIC29712BT
• Description: IC REG LDO 7.5A ADJ TO-220-5
• Manufacturer: Micrel Inc

Specifications of MIC29712BT

• Applications: Converter, Intel Pentium® Plus
• Voltage - Input: 2.25 ~ 16 V
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 16 V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: TO-220-5 (Straight Leads)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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
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
pinouts.
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:
Micrel, Inc.
Figure 3. The MIC29710 requires only two capacitors for
October 2006
•
•
•
•
Maximum ambient temperature, T
Output Current, I
Output Voltage, V
Input Voltage, V
operation
IN
OUT
.
OUT
®
regulators have identical
A
CE
saturation
®
8
First, we calculate the power dissipation of the regulator
from these numbers and the device parameters from this
datasheet.
Where the ground current is approximated by 3% of
IOUT. Then the heat sink thermal resistance is
determined with this formula:
Where T
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,
considered.
P
θ
JMAX
D
SA
= I
=
≤ 125°C and θ
OUT
especially
T
JMAX
× (1.03V
P
D
−
T
A
IN
−
CS
when
– V
(
θ
is between 0 and 2°C/W.
JC
OUT
+
)
θ
all
CS
MIC29710/29712
)
tolerances
M9999-101906
are