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www.fairchildsemi.com/fps
FPS
™
Design Guide
Green FPS™ Feature – Frequency Modulation for EMI
130kHz
131kHz
132kHz
133kHz
134kHz
135kHz
136kHz
137kHz
138kHz
2mS
A
B
C
130kHz
134kHz
138kHz
Sawtooth
Waveform
Ton
Vfb
Vdrain
Idrain
A
B
C
• Fixed frequency oscillators generate Electromagnetic
Interference (EMI) in a narrow band of the frequency spectrum
• Fairchild’s latest FPS devices modulate its frequency over a
±4kHz frequency range
• EMI is thus spread over a wider range of frequencies
• Allows simple EMI filters to be employed for meeting world
wide EMI requirements
• Refer to Application Note AN-4145 Electromagnetic
Compatibility for Power Converters for additional information
Below shows the frequency spectrum waveforms of a fixed frequency device versus a device that employs
frequency modulation.
100kHz Fixed Frequency
FSDH0165
134kHz with Frequency Modulation
FSD210
Peak Level Limit
Peak Level Limit
Peak Waveform
Quasi Peak Waveform
Summary of Contents for FPS Series
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