Micrel, Inc.
MIC2544A/2548A
Block Diagram
switch is enabled.
Functional Description
The MIC2548A features an internal latch which causes
the part to remain off after thermal shutdown until a reset
pulse is provided via the enable pin (pin 1). While in
current-limit, the thermal shutdown latch prevents on/off
cycling of the output.
The MIC2544A and MIC2548A are high-side N-channel
switches available with either active-high or active-low
enable inputs. Fault conditions turn-off or inhibit turn-on
of the output transistor and activate the open-drain error
flag transistor making it sink current-to-ground.
Refer to Figures 2a and 2b for timing diagram. The flag
remains low until reset.
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. If VOUT is greater than
VIN, current will flow from OUT to IN since the switch is
bidirectional when enabled.
Enable Input
EN must be driven logic high or logic low, or be pulled
high or low for a clearly defined input. Floating the input
may cause unpredictable operation. EN should not be
allowed to go negative with respect to GND, and VEN
should be less than or equal to VIN.
The output MOSFET and driver circuitry are also
designed to allow the MOSFET source to be externally
forced to a higher voltage than the drain (VOUT > VIN)
when the switch is disabled. In this situation, the
MIC2544A/48A avoids undesirable current flow from
OUT to IN. Both OUT pins must be connected together.
Thermal Shutdown
Thermal shutdown shuts off the output MOSFET and
signals the fault flag if the die temperature exceeds
150°C. 5°C of hysteresis prevents the switch from
turning on until the die temperature drops to 145°C.
Over-temperature detection functions only when the
M9999-043010
April 2010
14
MICREL [ MICREL SEMICONDUCTOR ]
