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FAN5307SX View Datasheet(PDF) - Fairchild Semiconductor

Part Name
Description
View to exact match
FAN5307SX
Fairchild
Fairchild Semiconductor Fairchild
FAN5307SX Datasheet PDF : 13 Pages
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N-channel rectifier switch. The device stays in sleep
mode until the output voltage falls below the low thresh-
old. The FAN5307 enters the PWM mode as soon as the
output voltage can no longer be regulated in PFM with
constant peak current.
100% Duty Cycle Operation
As the input voltage approaches the output voltage and
the duty cycle exceeds the typical 95%, the converter
turns the P-channel transistor continuously on. In this
mode the output voltage is equal to the input voltage
minus the voltage drop across the P-channel transistor:
VOUT = VIN – ILOAD × (RdsON + RL), where
RdsON = P-channel switch ON resistance
ILOAD = Output current
RL = Inductor DC resistance
Soft Start
The FAN5307 has an internal soft-start circuit that limits
the inrush current during start-up. This prevents possible
voltage drops of the input voltage and eliminates the out-
put voltage overshoot. The soft-start is implemented as a
digital circuit increasing the switch current in four steps to
the P-channel current limit (520mA). Typical start-up time
for a 10µF output capacitor and a load current of 200mA
is 500µs.
Short-Circuit Protection
The switch peak current is limited cycle by cycle to a typ-
ical value of 520mA. In the event of a output voltage
short circuit the device operates at minimum duty cycle,
therefore the average input current is typically 100mA.
8
www.fairchildsemi.com
FAN5307 Rev. 1.0.4
 

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