A8740 데이터 시트보기 (PDF) - Allegro MicroSystems

부품명

상세내역

일치하는 목록

A8740

Ultra Small Mobile Phone Xenon Photoflash Capacitor Charger with IGBT Driver

Allegro MicroSystems 

A8740

Ultra Small Mobile Phone Xenon Photoflash

Capacitor Charger with IGBT Driver

As soon as a sufficient voltage has built up at the output capaci-

tor, the IC enters Fast-Charging mode. In this mode, the next

switching cycle starts after the secondary side current has stopped

flowing, and the switch voltage has dropped to a minimum value.

A proprietary circuit is used to allow minimum-voltage switch-

ing, even if the SW pin voltage does not drop to 0 V. This enables

Fast-Charging mode to start earlier, thereby reducing the overall

charging time. Minimum-voltage switching is shown in figure 4.

During Fast-Charging mode, when VOUT is high enough (over

50 V), true zero-voltage switching (ZVS) is achieved. This

further improves efficiency as well as reduces switching noise. A

ZVS interval is shown in figure 5.

ISW

ISW

C4

C4

C2,C3

VSW

VBAT

VOUT

C1

Figure 4. Minimum-voltage switching: VOUT ≥ 35 V, VBAT = 5.5 V,

Ch1: VOUT = 20 V / div., Ch2: VBAT = 5 V / div., Ch3: VSW = 5 V / div.,

Ch4: ISW = 750 mA / div., t = 1 μs / div.

C2,C3

VSW

VBAT

VOUT

C1

Figure 5. True zero-voltage switching (ZVS): VOUT = 75 V, VBAT = 5.5 V,

Ch1: VOUT = 20 V / div., Ch2: VBAT = 5 V / div., Ch3: VSW = 5 V / div.,

Ch4: ISW = 750 mA / div., t = 0.5 μs / div.

Allegro MicroSystems, Inc.

11

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Share Link: