AS1363
Datasheet - Detailed Description
Power-OK
The AS1363 features a power-ok indicator that asserts when the output voltage falls out of regulation. The open-drain
POK output goes low when output voltage at OUT falls 6% below its nominal value. A 100kΩ pull-up resistor from POK
to a (typically OUT) provides a logic control signal.
POK can be used as a power-on-reset (POR) signal to a microcontroller or can drive an external LED to indicate a
power failure condition.
Note: POK is low during shutdown.
Current Limit
The AS1363 features current limiting circuitry that monitors the pass transistor, limiting short-circuit output current to
0.8A (typ). The circuitry of the AS1363 allows that the output can be shorted to ground for an indefinite period of time
without damaging the device.
Thermal Overload Protection
Integrated thermal overload protection limits the total power dissipation in the AS1363. When the junction temperature
(TJ) exceeds +170ºC typically, the pass transistor is turned off. Normal operation is continued when TJ drops approxi-
mately 20ºC.
Note: Regardless of the hysteresis, continuous short-circuit condition will result in a pulsed output.
Operating Region and Power Dissipation
Maximum power dissipation depends on the thermal resistance of the IC package and circuit board, the temperature
difference between the die junction and ambient air, and the rate of air flow.
The power dissipated in the device is given as:
PD = IOUT × (VIN – VOUT
)
(EQ 2)
The AS1363 can deliver up to 0.5A RMS and operates with input voltages up to +5.5V, but not at the same time. High
output currents can only be sustained when input/output differential voltages are low.
The maximum allowed power dissipation is 800mW at TAMB = +70ºC or:
T
J(max) – TAMB
-------------------------------------
PDMAX =
(EQ 3)
θ
JC + θCA
Where:
TJ(MAX) - TAMB is the temperature difference between the device die junction and the surrounding air.
θJC is the thermal resistance of the junction to the case.
θCA is the thermal resistance from the case through the PCB, copper traces, and other materials to the surrounding air.
Note: For best heat transfer, the copper area should be equally shared between the IN, OUT, and GND pins.
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