A8425 데이터 시트보기 (PDF) - Allegro MicroSystems

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A8425

High Current Photoflash Capacitor Charger with IGBT Driver for Two Li+ Batteries

Allegro MicroSystems 

A8425

High Current Photoflash Capacitor Charger

with IGBT Driver for Two Li+ Batteries

Timing and IGBT Interlock Function

The two TRIGGER signals are internally ANDed together. As

shown in the timing diagram, below, triggering is enabled when

the CHARGE pin is low. This feature improves noise immunity.

VIN

CHARGE

SW

VOUT

DONE

UVLO

Target VOUT

TRIGGER

T1

T2

T3

IGBTDRV

A

BC

D

E

F

Explanation of Events

A Start charging process by pulling CHARGE pin high, provided that VIN is above the UVLO level.

Triggering (T1) is locked during the charging process (CHARGE and ¯D¯¯O¯¯N¯¯E¯ pins are both high).

B Charging stops when VOUT reaches the target voltage level. Triggering (T2) is enabled after

completion of charging (CHARGE pin is high and ¯D¯¯O¯¯N¯¯E¯ pin is low).

C Start a new charging process with a low-to-high transition at the CHARGE pin.

D Pull the CHARGE pin low to put the controller into the low-power standby mode. Triggering (T3) is

always enabled when CHARGE is low.

E Charging does not start, because VIN is below the UVLO level when the CHARGE pin goes high.

F After VIN goes above the UVLO level, another low-to-high transition at the CHARGE pin is required

to start the charging process.

IGBT Drive Timing Definition

TRIGGER

GSOURCE

or GSINK

50%

50%

tdr

tr

tdf

tf

90%

10%

90%

10%

Allegro MicroSystems, Inc.

9

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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