ld7578j Leadtrend Technology, ld7578j Datasheet - Page 13

• Manufacturer Part Number: ld7578j
• Description: High Voltage Green-mode Pwm Controller With Over Temperature Protection
• Manufacturer: Leadtrend Technology

have a resistor connected at the MOSFET gate terminal (as
shown in Fig. 20) to provide extra protection for fault
conditions.
This external pull-low resistor is to prevent the MOSFET
from damage during power-on when the gate resistor R
disconnected. In such a fault condition, as show in Fig. 21,
the resistor R8 can provide a discharge path to avoid the
MOSFET from being falsely triggered by the current through
the gate-to-drain capacitor C
will be always pulled-low and persist in off-state.
Leadtrend Technology Corporation
LD7578J-DS-00 March 2009
UVLO(on)
UVLO(off)
PDR (8V)
AC input Voltage
1.05V
0.95V
V
(-)Latch
OUT
VCC
Switching
OTP
OTP Release
Non-Switching
Fig. 19
AC Off
GD
. Therefore, the MOSFET
Latch Released
AC On (Recycle)
www.leadtrend.com.tw
Switching
t
t
t
t
g
is
13
Protection Resistor on the Hi-V Path
In some other Hi-V processes and designs, there may be a
parasitic SCR between HV pin, Vcc and GND. As shown
in Fig. 22, a small negative spike on the HV pin may trigger
this parasitic SCR and cause latchup between Vcc and
Fig. 20
Fig. 21
i
=
Cgd
LD7578J
⋅
dV
dt
bulk