APL5317 查看數據表（PDF） - Anpec Electronics
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APL5317 Datasheet PDF : 17 Pages
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APL5317
Function Description
Internal Soft-Start
An internal soft-start function controls rising rate of the
output voltage to limit the surge current at start-up. The
typical soft-start interval is about 80µs.
Output Voltage Regulation
The APL5317 can work in either fixed or adjustable mode
by connecting the SET to GND or a resistor-divider which
receives the feedback voltage of the regulator. The output
voltage set by the resistor-divider is determined by:
VOUT
= 0.8 ⋅ 1 + R1
R2
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 to 100kΩ.
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.
Thermal Shutdown
A thermal shutdown circuit limits the junction tempera-
ture of APL5317. 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 by 40οC.The ther-
mal shutdown is designed with a 40οC hysteresis to lower
the average junction temperature during continuous ther-
mal overload conditions, extending lifetime of the device.
For normal operation, device power dissipation should
be externally limited, so that junction temperature will not
exceed 125οC.
Under-Voltage Lock Out (UVLO)
The APL5317 monitors the input voltage to prevent wrong
logic control. The UVLO function initiates a soft-start pro-
cess after input voltage exceeds its rising UVLO thresh-
old during power on. The UVLO function also shuts off
the output when the input voltage falls below its falling
threshold. Typical UVLO hysteresis voltage is 0.8V.
Shutdown Control
The APL5317 has an active-low shutdown function. Force
SHDN high (>1.6V) enables the V ; force SHDN low
OUT
(<0.4V) disables the V . SHDN is internally pulled low
OUT
by a resistor (3MΩ typical). If SHDN is not used, it will
connect to VIN for normal operation.
Copyright © ANPEC Electronics Corp.
10
Rev. A.4 - Mar., 2009
www.anpec.com.tw
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