MIC49500 Datasheet, PDF (9/11 Pages) Micrel Semiconductor – 5A Dual Supply, Low Voltage, High Bandwidth LDO

Micrel, Inc.
The heat sink may be significantly reduced in
applications where the maximum input voltage is
known and 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 the MIC49500
allow significant reductions in regulator power
dissipation and the associated heat sink without
compromising performance. When this technique is
employed, a capacitor of at least 1µF 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.
Minimum Load Current
The MIC49500, unlike most other high current
regulators, does not require a minimum load to
maintain output voltage regulation.
Power Sequencing
There is no power sequencing requirement for V_IN and
V_BIAS, giving more flexibility to the user.
MIC49500
Adjustable Regulator Design
The MIC49500 adjustable version allows
programming the output voltage anywhere between
0.7Vand 6V. Two resistors are used. The resistor
value between VOUT and the adjust pin should not
exceed 10kΩ. Larger values can cause instability. The
resistor values are calculated by:
V_OUT
R1 = R2 ×
±1
0.7
Where V_OUT is the desired output voltage.
Enable
The fixed output voltage versions of the MIC49500
feature an active high enable input (EN) that allows
on-off control of the regulator. Current drain reduces
to “zero” when the device is shutdown, with only
microamperes of leakage current. The EN input has
TTL/CMOS compatible thresholds for simple logic
interfacing. EN may be directly tied to V_IN and pulled
up to the maximum supply voltage.
November 2005
9
M9999-110805
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