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UCC2808A: Voltage and current feedback calculation

Other Parts Discussed in Thread: TL431

Hi,


We are using UCC2808A for our isolated power supply design, but datasheet doesn't have much info on designing. Have some of following doubts:

Q1. for type-II compensator across TL431, what decides the frequency of poles and zero ?

Q2. Assuming cross-over frequency as 1/10th of converter's switching frequency, how far is it correct to consider.

Q3. there's no pull-up Resistor provided from NPN Photo-transistor (Pin#5 of H11A1) to Vdd, where as most of TI application note has included it.

Q4. Compensation loop across COMP-FB pin, current sense circuit.

Any assistance on above queries will be very kind and helpful of you.

Thanks & Regards,

Varun Jaiswal