sg6741a Fairchild Semiconductor, sg6741a Datasheet - Page 9

• Manufacturer Part Number: sg6741a
• Description: Sg6741a ? Highly Integrated Green-mode Pwm Controller
• Manufacturer: Fairchild Semiconductor

© 2008 Fairchild Semiconductor Corporation
SG6741A • Rev. 1.0.1
V
V
damage due to abnormal conditions. Once the V
voltage is over the V
(V
disabled until the V
then starts again. Over-voltage conditions are usually
caused by open feedback loops.
Limited Power Control
The FB voltage increases every time the output of the
power supply is shorted or overloaded. If the FB voltage
remains higher than a built-in threshold for longer than
t
turned off, the supply voltage V
D-OLP
DD
DD
DD-OVP
over-voltage protection has been built in to prevent
Over-voltage Protection (OVP)
, PWM output is turned off. As PWM output is
) and lasts for t
DD
DD
voltage drops below the UVLO,
over-voltage protection voltage
D-VDDOVP
DD
, the PWM pulses are
begins decreasing.
DD
9
When V
the controller is totally shut down. V
the turn-on threshold voltage of 16V through the startup
resistor until PWM output is restarted. This protection
feature continues as long as the overloading condition
persists.
overheating due to overloading conditions.
Noise Immunity
Noise on the current sense or control signal may cause
significant pulse-width jitter, particularly in continuous-
conduction mode. Slope compensation helps alleviate
this problem. Good placement and layout practices
should be followed. Avoiding long PCB traces and
component leads, locating compensation and filter
components near the SG6741A, and increasing the
power MOS gate resistance improve performance.
DD
This
goes below the turn-off threshold (~10.5V)
prevents
the
power
DD
is charged up to
supply
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from