Advanced Power

Electronics Corp.

APE1701

BLOCK DIAGRAM

FUNCTION DESCRIPTION

VCC

VSS

SW

FEEDBACK

EN

5

This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor

must be presented at this pin to minimize voltage transients and to supply the switching currents

needed by the regulator.

Circuit ground.

Internal switch. The voltage at this pin switches between (+VCC – VSAT) and approximately –

0.5V, with a duty cycle of approximately VOUT / VCC. To minimize coupling to sensitive circuitry, the

PC board copper area connected to this pin should be minimized.

Senses the regulated output voltage to complete the feedback loop.

150kHz

OSC.

START

UP

+

+

+

_

Thermal

Shutdown

CONTROL

+

DRIVER

COMP.

COMP.

Vss

SW

EN

FB

200mV

220mV

SWITCH

COMP.

Current

limit

+

_

AMP

COMP.

CURRENT

SOURCE

BIAS

1.235V

REFERENCE

2.5V

REGULATOR

R2

R1

ADJ : R2=0Ω, R1=OPEN

Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the

total input supply current to approximately 100uA. Pulling this pin below a threshold voltage of

shuts the regulator down. If this shutdown feature is not needed, the EN pin can be wired to the ground

pin.