ld7576a Leadtrend Technology, ld7576a Datasheet - Page 12

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

OVP (Over Voltage Protection) on Vcc - Auto
Recovery
The maximum V
mostly for 30V. To prevent the V
LD7576A is implemented with OVP function on Vcc.
Whenever the Vcc voltage is higher than the OVP
threshold, the output gate drive circuit will be shutdown
simultaneously and the switching of the power MOSFET is
disabled until the next UVLO(on).
The Vcc OVP functions of LD7576A is auto-recoverable.
If the OVP condition, usually caused by open-loop of
feedback, is not released, the Vcc will trip the OVP level
again and re-shutdown the output.
hiccup mode as shown in Figure 18.
Otherwise, when the OVP condition is removed, the Vcc
level will be resumed and the output will automatically
return to the normal operation.
Leadtrend Technology Corporation
LD7576A-DS-00b November, 2009
GS
ratings of the power MOSFETs are
Fig. 17
GS
enter fault condition,
The Vcc works in
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12
Pull-Low Resistor on the Gate Pin of
MOSFET
The LD7576A is internally equipped with an anti-floating
resistor on the OUT pin to protect the output from
abnormal operation or false triggering of MOSFET. Even
so, we still recommend adding an external one on the
MOSFET gate terminal to provide more protection in case
of disconnection of gate resistor R
19.
In such single-fault condition, as show in figure 20, 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
MOSFET is always pulled low and placed in the off-state
even if the gate resistor is disconnected or opened in any
case.
Fig. 18
LD7576A
G
during power-on in Fig.
GD
. Therefore, the