LD7577JA 데이터 시트보기 (PDF) - Unspecified

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LD7577JA

High Voltage Green-Mode PWM Controller with Brown-Out Protection

Unspecified 

Line

Voltage

LD7577JA

pulled low to maintain in a off-state no matter the gate

resistor is disconnected or opened in any case.

V BNO

4.16

3.92

1.05V

Vcc

UVLO- ON

UVLO- OFF

AC OK area

OUT

Switching

Non- Switching

Fig.21

t

t

AC OK area

t

Switching

t

Pull-Low Resistor on the Gate Pin of

MOSFET

An anti-floating resistor is implemented in the OUT pin to

prevent any uncertain output, which may cause MOSFET

to work abnormally or false trigger on. However, such

design may not apply in all the disconnection of gate

resistor RG. It is still strongly recommended to have a

resistor connected at the MOSFET gate terminal (as

shown in figure 22) to provide extra protection in fault

conditions.

This external pull-low resistor is to prevent the MOSFET

from being damaged during power-on when the gate

resistor is disconnected. In such single-fault condition,

as shown in figure 23, the resistor R8 can provide a

discharge path to avoid the MOSFET from being

false-triggered by the coupling through the gate-to-drain

capacitor CGD. Therefore, the MOSFET gate should be

Fig. 22

i = Cgd ⋅ dVbulk

dt

Fig. 23

Leadtrend Technology Corporation

LD7577JA-DS-00b August 2010

14

www.leadtrend.com.tw

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