APL5315(2007) Ver la hoja de datos (PDF) - Anpec Electronics
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APL5315 Datasheet PDF : 16 Pages
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APL5315
Typical Application Circuits (Cont.)
2. Adjustable Output Voltage Mode
VIN
CIN
1µF
Enable
APL5315
3
VIN
4
VOUT
1 SHDN
5
SET
GND
2
Shutdown
Functional Descriptions
VOUT
= 0.8 ⋅ 1+
R1
R2
VOUT
R1
COUT
2.2µF
R2
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 APL5315 can works 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
recommended value of R2 is in the range of 100~100KΩ.
An error amplifier working with a temperature compen-
sated 0.8V reference and an output PMOS regulates the
output to the presetting voltage. The error amplifier
designed with high bandwidth and DC gain provides
very fast transient response and less load regulation.
It compares the reference with the feedback voltage and
amplifies the difference 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 APL5315. When the junction temperature exceeds
+160οC, a thermal sensor turns off the output PMOS,
allowing the device to cool down. The regulator regu-
lates the output again through initiation of a new soft-
start cycle after the junction temperature cools by 40οC.
The thermal shutdown designed with a 40οC hysteresis
lowers the average junction temperature during continu-
ous 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
exceed 125οC.
Under-Voltage Lock Out (UVLO)
The APL5315 monitors the input voltage to prevent
wrong logic control. The UVLO function initiates a soft-
start process after input voltage exceeds its rising
UVLO threshold during power on. The UVLO function
also shuts off the output when the input voltage falls
below it’s falling threshold. Typical UVLO hysteresis
voltage is 0.8V.
Shutdown Control
The APL5315 has an active-low shutdown function. Force
SHDN high (>1.6V) enables the VOUT; force SHDN low
(<0.4V) disables the V . SHDN is internally pulled low
OUT
by a resistor (3MΩ typical). If it is not used, connect to VIN
for normal operation.
Copyright © ANPEC Electronics Corp.
9
Rev. A.2 - Mar., 2007
www.anpec.com.tw
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