FAN400A Fairchild Semiconductor, FAN400A Datasheet - Page 10

• Manufacturer Part Number: FAN400A
• Description: This highly integrated PWM controller provides several features to enhance the performance of low-power flyback converters
• Manufacturer: Fairchild Semiconductor

© 2008 Fairchild Semiconductor Corporation
FAN400A Rev. 1.0.2
Operation Description
Slope Compensation
The sensed voltage across the current sense resistor is
used for current mode control and pulse-by-pulse
current limiting. The built-in slope compensation
improves
prevents sub-harmonic oscillations that normally would
occur because of peak current mode control. A
positively sloped, synchronized ramp is activated with
every switching cycle. The slope of the ramp is:
0.33 ×
Duty(max.)
Duty
power
supply
stability.
(Continued)
Furthermore,
(1)
it
10
Noise Immunity
Noise from the current sense or the control signal may
cause significant pulse-width jitter, particularly in
continuous-conduction
helps alleviate this problem. Good placement and
layout practices should be followed. The designer
should avoid long PCB traces and component leads.
Compensation and filter components should be located
near the FAN400A. Finally, increasing the power-MOS
gate resistance is advised.
mode.
Slope
compensation
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