ld7578h Leadtrend Technology, ld7578h Datasheet - Page 15

• Manufacturer Part Number: ld7578h
• Description: High Voltage Green-mode Pwm Controller With Over Temperature Protection
• Manufacturer: Leadtrend Technology

discharge path to avoid the MOSFET from being
false-triggered by the coupling through the gate-to-drain
capacitor CGD. Therefore, the gate of MOSFET should
be pulled low to maintain MOSFET in a off-state no matter
the gate resistor is disconnected or opened in any case.
Leadtrend Technology Corporation
LD7578H-DS-00 February 2010
Fig. 20
Fig. 21
i
=
Cgd
⋅
dV
dt
bulk
www.leadtrend.com.tw
15
Protection Resistor on the Hi-V Path
In some other Hi-V processes and designs, there is
probably some parasitic SCR caused around HV pin, V
and GND. As shown in figure 22, a small negative spike
in the HV pin may trigger this parasitic SCR and cause the
latchup between V
damage the chip easily because of the equivalent
short-circuit induced.
LD7578H has eliminated the parasitic SCR efficiently.
Figure 23 shows the equivalent circuit of LD7580’s Hi-V
structure. It tells LD7578H is capable to sustain negative
voltage and superior than similar products. Even though,
a 40KΩ resistor is still recommended to be placed on the
Hi-V path
CC
and GND.
Fig. 22
Fig. 23
LD7578H
Such latchup will
CC