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CS and REF of UCC28220

Masami Michino
Genius 5070 points
Other Parts Discussed in Thread: UCC28220


Dear, All

A customer would like to use UCC28220 as a flyback controller.
There are 2 questions about UCC28220 to use.

Question 1
About CS pin.
A customer doesn't want to use a Current Sense Transformers.
Are they able to input to CS pin using sense resistance with Op-AMP?

Question 2
About REF pin.
A customer would like to use output of REF outside.
Is it usable outside?
If it is usable, how many mA is it?

Thanks, Masami M.

  • 0
    TI__Mastermind 34465 points
    Hi Masami,
    The CS1 and CS2 inputs can be used with a resistor sensing the current. The input voltage range is 0 to 1.5V which in most cases requires the use of an OPAMP circuit. An issue with using this method of current sensing is that the sensed voltage is more prone to noise pickup from the power MOSFET switching. Therefore care must be used in the circuit layout and a differential type OPAMP is recommended. Also the GND pin of the UCC28220 should be routed away from the negative return of the power and tied together at a single point.

    VREF is rated at 10mA min when the outputs are not switching so a realistic number is probably 5mA in an actual application
    and it is important that VREF be decoupled with at least 0.1uF high frequency ceramic capacitors.

    Regards,
    John Griffin
  • 0 in reply to John Griffin1
    Genius 5070 points
    Hi, John Griffin-san,

    Thank you for your reply.
    I answer it to the customer.

    Thanks, Masami M.