BD8966FVM(2009) Просмотр технического описания (PDF) - ROHM Semiconductor

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BD8966FVM
(Rev.:2009)

Low Noise High Efficiency Step-down Switching Regulator with Built-in Power MOSFET

ROHM Semiconductor 

BD8966FVM

Technical Note

●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

N-channel MOS FET is turned OFF), and an inductor current IL increases. The current comparator (Current Comp)

receives two signals, a current feedback control signal (SENSE: Voltage converted from IL) and a voltage feedback

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.

VOUT

SENSE

Current

Comp

RESET

Level

RQ

Shift FB

Gm Amp.

SET S

ITH

OSC

Driver

Logic

IL

SW

Load

VOUT

Fig.20 Diagram of current mode PWM control

Current

Comp

SET

RESET

SW

IL

VOUT

PVCC

SENSE

FB

GND

GND

GND

IL(AVE)

VOUT(AVE)

Fig.21 PWM switching timing chart

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

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2009.05 - Rev.A

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