MIC2026A_09 Datasheet, PDF (11/16 Pages) Micrel Semiconductor – Dual-Channel Power Distribution Switch

Micrel, Inc.
Block Diagram
MIC2026A/2076A
MIC2026A/2076A Block Diagram
Functional Description
Input and Output
IN is the power supply connection to the logic circuitry
and the drain of the output MOSFET. OUT is the source
of the output MOSFET. In a typical circuit, current flows
from IN to OUT toward the load when the switch is
enabled.
An important consideration in choosing a switch is
whether it has “reverse voltage protection.” This is
accomplished by eliminating the body diode during the
fabrication process. Reverse voltage protection is
important when the switch is disabled and a voltage is
presented to the OUT pin that is greater than the VIN pin
voltage. The reverse voltage protection prevents current
flow in the reverse path from OUT to IN.
On other hand when the switch is enabled the switch is
bidirectional. In this case when a voltage is presented to
the OUT pin that is greater than the VIN voltage, current
will flow from OUT to IN.
Thermal Shutdown
Thermal shutdown is employed to protect the device
from damage should the die temperature exceed safe
margins due mainly to short circuit faults. Each channel
employs its own thermal sensor. Thermal shutdown
shuts off the output MOSFET and asserts the FLG
July 2009
output if the die temperature reaches 140°C and the
overheated channel is in current limit. The other channel
is not affected. If however, the die temperature exceeds
160°C, both channels will be shut off.
The MIC2026A will automatically reset its output when
the die temperature cools down to 120°C. The
MIC2026A’s output and FLG signal will continue to cycle
on and off until the device is disabled or the fault is
removed. Figure 2 depicts typical timing.
On the other hand, the MIC2076A’s output will be turned
off, and remain off until the MIC2076A is reset. This is
often called latched output, that is, the output is “latched”
off and stays off. This is different from the MIC2026A’s
output that will cycle on and off. The MIC2076A will
latch off the output when the MIC2076A is in current
limiting and the switch goes in to thermal shutdown.
Upon entering thermal shutdown, the output will be
immediately latched off. The MIC2076A (latched output)
can be reset by any of the following three methods:
1. Remove the fault load
2. Toggle the EN (Enable) pin
3. Cycle VIN (input power supply)
Resetting the MIC2076A will return it to normal
operation.
Depending on PCB layout, package, ambient
temperature, etc., it may take several hundred
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M9999-072309-B
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