Copyright ANPEC Electronics Corp.
Rev. A.5 - Jul., 2010 www.anpec.com.tw9
APL5601/5602
Function Description
A thermal shutdown circuit limits the junction tempera-
ture of APL5601/5602. When the junction temperature
exceeds +150oC, the thermal shutdown circuitry disables
the output, allowing the device to cool down. The output
circuitry is enabled again after the junction temperature
cools down by 40oC, resulting in a pulsed output during
continuous thermal overload conditions. Thermal pro-
tection is designed to protect the IC in the event of over
temperature conditions. For reliable operation, the junc-
tion temperature cannot exceed TJ=+125 oC.
Under Voltage Lockout (UVLO)
The APL5601/5602 regulators have built-in under-volt-
age lock-out circuits to keep the output shuting off until
internal circuitry is operating properly. The UVLO function
initiates a soft-start process after input voltage exceeds
its rising UVLO threshold during power on. Typical UVLO
threshold is 2.5V with 0.15V hysteresis.
Soft-Start
The APL5601/5602 provide an internal soft-start circuitry
to control rise rate of the output voltage and limit the cur-
rent surge during start-up. Approximate 20µs delay time
after the VIN is over the UVLO threshold, the output voltage
starts the soft-start. The typical soft-start interval is about
130µs.
Current-Limit
The APL5601/5602 provides a current-limit circuitry, which
monitors and controls P-MOS’s gate voltage, limiting the
output current to 700mA. For reliable operation, the de-
vice should not be operated in current-limit for extended
period.
Short Circuit Current-Limit
When the output voltage drops below 0.6V, which is
caused by the over load or short circuit, the internal short
circuit current-limit circuitry limits the output current down
to 250mA. The short circuit current-limit is used to reduce
the power dissipation during short circuit condition. In
some high VIN-VOUT conditions, if the junction tempera-
ture is over the thermal shutdown temperature, the de-
vice will enter the thermal shutdown. Please refer to the
section on thermal considerations for power dissipation
calculations. The short circuit current-limit has a blank-
ing time feature after the UVLO threshold is reached, so
that it will avoid the output causing short circuit current-
limit protection during start-up; the blanking time is about
600µs.
Thermal Shutdown