APL5913 Anpec Electronics, APL5913 Datasheet - Page 12

• Manufacturer Part Number: APL5913
• Description: 0.8V Reference Ultra Low Dropout Linear Regulator
• Manufacturer: Anpec Electronics

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APL5913
Functional Description (Cont.)
Output Voltage Regulation (Cont.)
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
NMOS which provides load current from VIN to VOUT.
Current-Limit
The APL5913 monitors the current via the output
NMOS and limits the maximum current to prevent load
and APL5913 from damages during overload or short-
circuit conditions.
Under-Voltage Protection (UVP)
The APL5913 monitors the voltage on FB pin after
soft-start process is finished. Therefore the UVP is
disable during soft-start. When the voltage on FB pin
falls below the under-voltage threshold, the UVP
circuit shuts off the output immediately. After a while,
the APL5913 starts a new soft-start to regulate output.
Thermal Shutdown
A thermal shutdown circuit limits the junction temperature
of APL5913. When the junction temperature exceeds
+150°C, a thermal sensor turns off the output NMOS,
allowing the device to cool down. The regulator regulates
the output again through initiation of a new soft-start
cycle after the junction temperature cools by 50°C,
resulting in a pulsed output during continuous thermal
overload conditions. The thermal shutdown designed
Application Information
Power Sequencing
The power sequencing of VIN and VCNTL is not necessary
to be concerned. But do not apply a voltage to VOUT
for a long time when the main voltage applied at VIN is
not present. The reason is the internal parasitic diode
from VOUT to VIN conducts and dissipates power
without protections due to the forward-voltage.
Copyright
Rev. A.4 - May., 2005
ANPEC Electronics Corp.
12
with a 50
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 temperatures will
not exceed +125°C.
Enable Control
The APL5913 has a dedicated enable pin (EN). A logic
low signal (V
the output. Following a shutdown, a logic high signal
re-enables the output through initiation of a new
softstart cycle. Left open, this pin is pulled up by an
internal current source (10 A typical) to enable
operation. It’ s not necessary to use an external transistor
to save cost.
Power-OK and Delay
The APL5913 indicates the status of the output voltage
by monitoring the feedback voltage (V
As the V
threshold (V
perform a delay time. At the end of the delay time, the
IC turns off the internal NMOS of the POK to indicate
the output is OK. As the V
falling Power-OK threshold (V
turns on the NMOS of the POK to indicate the output
is not OK without a delay time.
Output Capacitor
The APL5913 requires a proper output capacitor to
maintain stability and improve transient response over
temperature and current. The output capacitor selection
is to select proper ESR(equivalent series resistance)
and capacitance of the output capacitor for good stability
and load transient response.
FB
o
C hysteresis lowers the average junction
rises and reaches the rising Power-OK
POK
EN
< 0.3V) applied to this pin shuts down
), an internal delay function starts to
FB
PNOK
falls and reaches the
), the IC immediately
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FB
) on FB pin.