BD8966FVM

Technical Note

6/14

www.rohm.com

2009.05 - Rev.A

© 2009 ROHM Co., Ltd. All rights reserved.

●

Operation

BD8966FVM is a synchronous rectifying step-down switching regulator that achieves faster transient response by employing

current mode PWM control system.

○

Synchronous rectifier

It does not require the power to be dissipated by a rectifier externally connected to a conventional DC/DC converter IC,

and its P.N junction shoot-through protection circuit limits the shoot-through current during operation, by which the power

dissipation of the set is reduced.

○

Current mode PWM control

Synthesizes a PWM control signal with a inductor current feedback loop added to the voltage feedback.

・

PWM (Pulse Width Modulation) control

The oscillation frequency for PWM is 1 MHz. SET signal form OSC turns ON a P-channel MOS FET (while a

control signal (FB), and issues a RESET signal if both input signals are identical to each other, and turns OFF the

P-channel MOS FET (while a N-channel MOS FET is turned ON) for the rest of the fixed period. The PWM control

repeat this operation.

Fig.20 Diagram of current mode PWM control

OSC

Level

Shift

Driver

Logic

RQ

S

SW

ITH

Current

Comp

Gm Amp.

SET

RESET

FB

Load

SENSE

Fig.21 PWM switching timing chart

Current

Comp

SET

RESET

SW

PVCC

GND

GND

GND

SENSE

FB