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UC2845AQ / to disable OUTPUT

K.Yaita
Guru 29720 points
Other Parts Discussed in Thread: UC2845AQ

Hi TI members,

I was asked the following question from my customer.
Is there any method to disable OUTPUT except applying COMP pin to low?
He assumes VCC is applied in this case.

Best Regards,
Yaita / Japan disty

  • 0
    TI__Guru* 85926 points

    Hello Yaita,

     

    I reviewed the block diagram and there is a VREF good comparator. If you pull down on VREF this would shut down the device.  However this short circuit current is 60 + mA so this is not advisable.

    The other option is to force the device into UVLO by dropping or removing the VDD voltage.

    I did review the data sheet and the comp pin is current limited to you can pull it down to ground to demand 0% duty cycle. The block diagram in figure 14 has this limited to 500uA.  The data sheet give a 500 uA typical.

    I know that your customer was looking for other options to shut down the gate drive; however, pulling down on the COMP pin is probably the best choice.

    Regards,

    Mike

  • 0 in reply to Mike O'
    Guru 29720 points

    Hi Mike-san,

    I appreciate for your support!

    >If you pull down on VREF this would shut down the device.  However this short circuit current is 60 + mA so this is not advisable.
    I understood I should see Figure 5.
    Could you tell me threshold voltage of VREF good comparator as a reference?

    In addition, Can I see the following datasheet for UC2845AQ?
    http://www.tij.co.jp/jp/lit/ds/symlink/uc2845.pdf
    I have seen the following datasheet until now.
    http://www.tij.co.jp/jp/lit/ds/symlink/uc2845aq.pdf

    Best Regards,
    Yaita