Output Voltage Regulation
The APL5325 is an adjustable low dropout linear
regulator. The output voltage set by the resistor-divider is
= 0.8 ⋅ 1 +
Where R1 is connected from VOUT to SET with Kelvin
sensing and R2 is connected from SET to GND. The rec-
ommended value of R2 is in the range of 100 to100kΩ.
An error amplifier works with a temperature compensated
0.8V reference and an output PMOS regulates the output
to the presetting voltage. The error amplifier is designed
with high bandwidth and DC gain provides very fast tran-
sient response and less load regulation. It compares the
reference with the feedback voltage and amplifies the dif-
ference to drive the output PMOS which provides load
current from VIN to VOUT.
A thermal shutdown circuit limits the junction tempera-
ture of APL5325. When the junction temperature exceeds
+160οC, a thermal sensor turns off the output PMOS, al-
lowing the device to cool down. The regulator regulates
the output again through initiation of a new soft-start cycle
after the junction temperature is cooled down by 40oC.
The thermal shutdown is designed with a 40oC hyster-
esis to lower the average junction temperature during
continuous thermal overload conditions, extending life-
time of the device.
For normal operation, device power dissipation should
be externally limited so that junction temperature will not
The APL5325 has an active-low shutdown function. Force
SHDN high (>1.6V) enables the V ; force SHDN low
(<0.4V) disables the VOUT. SHDN is internally pulled low
by a resistor (3mΩ typical). If it is not used, connect to VIN
for normal operation.
Copyright © ANPEC Electronics Corp.
Rev. A.1 - Nov., 2008