SC4524A Datasheet, PDF (5/18 Pages) Semtech Corporation – 28V 2A Step-Down Switching Regulator

SC4524A
Pin Descriptions
SO-8
1
2
3
4
5
6
7
8
9
Pin Name Pin Function
SW
Emitter of the internal NPN power transistor. Connect this pin to the inductor, the freewheeling diode and the
bootstrap capacitor.
IN
ROSC
GND
SS/EN
COMP
Power supply to the regulator. It is also the collector of the internal NPN power transistor. It must be closely by-
passed to the ground plane.
An external resistor from this pin to ground sets the oscillator frequency.
Ground pin
Soft-start and regulator enable pin. A capacitor from this pin to ground provides soft-start and overload hiccup
functions. Hiccup can be disabled by overcoming the internal soft-start discharging current with an external pull-
up resistor connected between the SS/EN and the IN pins. Pulling the SS/EN pin below 0.2V completely shuts off
the regulator to low current state.
The output of the internal error amplifier. The voltage at this pin controls the peak switch current. A RC compensa-
tion network at this pin stabilizes the regulator.
FB
The inverting input of the error amplifier. If V_FB falls below 0.8V, then the switching frequency will be reduced to
improve short-circuit robustness (see Applications Information for details).
BST
Exposed Pad
Supply pin to the power transistor driver. Tie to an external diode-capacitor bootstrap circuit to generate drive
voltage higher than V_IN in order to fully enhance the internal NPN power transistor.
The exposed pad serves as a thermal contact to the circuit board. It is to be soldered to the ground plane of the
PC board.