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UCC28950: The operation when EA+ is not entered.

Guru 10385 points
Part Number: UCC28950

Hi team,

I'd like to know the operation when EA+ is not entered.
What happens to the output when EA+ is 0V when there is an input in VDD and EN/SS?
I want to know when there is no input and input in EA-.

Sincerely.
Kengo.

  • Hello,

    The common mode range of the amplifier is 0.5 V to 3.6V.  So the amplifier should not be set with EA+ = 0.  The device does have a VREF good comparator so during power up  the controller should not respond to 0 V on EA+ when VERF is not operation.

    Condition two should not occur.

    When EA- is at zero voltage and EA+ is in the common mode range.  The amplfier's output should drive high demanding duty cycle.

    Regards,

  • Hi Mike,

    Thank you for your reply.

    There is a description as follows in the test condition.


    I think that there is no problem with an input of 0.5V or less.
    Could you tell me what the output looks like when EA + is 0V.

    Sincerely.
    Kengo.

  • Hello,

    You should not set EA + to zero volts.  This is the reference voltage you are controlling the loop too.  We have not tested the EA+ with less than 0.5V because this is outside the common mode range.

    If you are testing this amplifier open loop and bringing down the EA + to 0V you may have misbehavior due to the Error Amplifier offset which is +/- 7 mV.

    The other issue you may be having is the amplifier was not design to have an EA of less than -0.5V.  This is specified in the VICIM range in the data sheet.

    Regards,

  • Thank you for your quick reply.

    I'm sorry, I don't understand well.
    What does the test condition mean?

    Does this mean that this condition is excluded?

    And, should I if I connect EA+ to VREF as in the datasheet, it won't be 0V?

    Sincerely.
    Kengo.

  • Hello,

    The common mode range is 0.5V to 3.6V.

    The -0.4V to 0.5V is not the common mode range and is listed as a test condition.

    Not sure why they listed this as a test condition because the common range is 0.5 to 3.6V.

    I believe this is type-o in the test conditions.  

    Regards,