ld7576a Leadtrend Technology, ld7576a Datasheet - Page 13

• Manufacturer Part Number: ld7576a
• Description: Green-mode Pwm Controller With High-voltage Start-up Circuit And Adjustable Olp Delay Time
• Manufacturer: Leadtrend Technology

Protection Resistor on the Hi-V Path
In some other Hi-V process and design, there may be a
parasitic SCR caused around HV pin, Vcc and GND. As
shown in figure 21, a small negative spike on the HV pin
may trigger this parasitic SCR and cause latchup between
Vcc and GND. It will intend to damage the chip because
Leadtrend Technology Corporation
LD7576A-DS-00b November, 2009
Fig. 19
Fig. 20
i
=
Cgd
⋅
dV
www.leadtrend.com.tw
dt
bulk
13
of the equivalent short-circuit induced by such latchup
behavior.
Leadtrend’s proprietary of Hi-V technology eliminate
parasitic SCR in LD7576A.
equivalent
Accordingly, LD7576A is more capable to sustain negative
voltage than other similar products. Nevertheless, a 40KΩ
resistor is recommended to be added on the Hi-V path to
play as a current limit resistor whenever a negative voltage
is applied.
Frequency Trembling
The LD7576A is built in with adjustable frequency
trembling function, which provides the power supply
designers to optimize EMI performance and system cost.
The Trembling frequency was internally set for ±4KHz
when incorporating with 65KHz switching frequency. On
circuit
of
LD7576A
Fig. 21
Fig. 22
LD7576A
Figure 22 shows the
of
Hi-V
structure.