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TPS560200: Accuracy of zero-cross current to enter into pulse skip mode

Takahiro Saito
Expert 5365 points
Part Number: TPS560200
Other Parts Discussed in Thread: TPS561208, TLV62565

Hi team,

My customer wants to use TPS560200 in PWM mode not to affect the switching noise to other IC.

I understand TPS560200 enters the pulse skip mode when the integrated current sense amp detect zero-cross of inductor current.

If possible, could you give me the accuracy of zero current detection? How much does the zero-cross current for entering PSM mode vary?

Regards,

Saito  

  • 0
    TI__Mastermind 18510 points

    Hi Saito,

    Drafty you can cal the 1/2 pk-pk current of inductor based on Vin/Vout/L/Fsw, which represents enter PSM at that DC loading point.

    And if customer want to use PWM part, TPS561208 should be a choice.

    Yuchang

  • 0 in reply to Yuchang Zhang
    TI__Expert 5365 points

    Hi Yuchang-san,

    Thank you for your answer. Customer calculated the threshold current by fomula (1) in datasheet.

    I think the device detects the zero valley current of inductor current. Could you check the accuracy of the zero current detection?

    Regards,

    Saito

  • 0 in reply to Takahiro Saito
    TI__Mastermind 18510 points

    Saito-San,

    Yes, the IC detects the valley Zero inductor value to enter DCM, what I thought is customer would like to get the DC loading point of entering DCM, if so, the formula 1 is for that.

    I would let team guy help to check the ZC corrossing variation if customer really need it, before that I Suppose the inductor Zero detection limitation is +/-300mA. why customer would like to get this? What I mean is if they don’t want to use PSM, Why don’t use a FCCM part directly.

    Yuchang

  • 0 in reply to Yuchang Zhang
    TI__Expert 5365 points

    Hi Yuchang-san,

    They were going to use TLV62565 originally, but they found the PFM ripple affects to the other devices performance just before the mass production. Since they are in just before mass production, they can't change the layout. They tried to change external components, but there was no improvement. As a try, they changed TLV62565 to p2p device, TPS560200, they could see the improvement. So, they wants to go with TPS560200. I think there is no p2p FCCM device in TI portfolio. So, they need to use TPS560200. 

    When TPS560200 entered into PFM mode, they found the issue again. So, they are going to use TPS560200 in CCM mode by flowing an extra load current with dammy load at the expense of the power consumption. They wants to know how much extra load current is needed to keep TPS560200 in CCM mode. That's why customer ask us the accuracy of zero valley current detection.

    I appreciate if you help chencking the current detection accuracy.

    Regards,

    Saito  

       

  • 0 in reply to Takahiro Saito
    TI__Mastermind 18510 points

    Hi Saito-san,

    Seems no P2P solution for 560200, please close this thread first and let me forward this to lead engineer to look into this by Email.

    Yuchang