FAN6753 Fairchild Semiconductor, FAN6753 Datasheet - Page 10

• Manufacturer Part Number: FAN6753
• Description: The highly integrated FAN6753 PWM controller provides several features to enhance the performance of flyback converters
• Manufacturer: Fairchild Semiconductor

© 2009 Fairchild Semiconductor Corporation
FAN6753 • Rev. 1.0.3
Functional Description
Limited Power Control
The feedback (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
PWM output is turned off, V
When V
controller is totally shut down. V
turn-on threshold voltage of 15.5V through the startup
resistor until PWM output is restarted. This protection
feature continues as long as the overloading condition
persists.
Over-Temperature Protection
(Internal OTP)
The built-in temperature-sensing circuit shuts down
PWM output once the junction temperature exceeds
135°C. While PWM output is shut down, V
drops to the UVLO voltage (around 7.5V). Then V
charges up to the startup threshold voltage of 15.5V
through the startup resistor until PWM output is
restarted.
repeatedly as long as the temperature remains above
130°C. The temperature hysteresis window for the OTP
circuit is 25°C.
DD
goes below the turn-off threshold (~9.5V), the
This
D-OLP
“hiccup”
, PWM output is turned off. As
DD
mode
begins decreasing.
DD
(Continued)
is charged up to the
protection
DD
gradually
occurs
DD
10
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 FAN6753, and increasing the
power MOS gate resistance also improve performance.
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