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TPS62560 /phase margin

Tsukui Yusuke
Guru 21930 points
Other Parts Discussed in Thread: TPS62560, TPS62230, TLV62565, TLV62080

Hi,

Could you review an attached circuit?
Customer want advice about phase margin and stability of the output voltage.

2514.TPS62560.pdf

I tried to confirm with the simulation tool.
However,It did not correspond to phase measurement.
we have seen TPS62230 support in Webench and both TPS62560 & TPS62230 looks very similar part.
So can we use TPS62230 webench simulation for TPS62560 part?

Could you give me your advice?

[my e-mail address]
tsukui-y@clv.macnica.co.jp

Best Regards,
Yusuke/Japan Disty

  • 0
    TI__Guru*** 142860 points
    No, the TPS62560 and TPS62230 are completely different devices with different control methods, as explained in the D/S.

    The attached TINA model used the transient model. You cannot measure the bode plot without an average model.

    As well, the load current is only 70 mA. This is PFM mode, where the bode plot is not meaningful.

    Finally, this is a very old device for which the TLV62080 or TLV62565 would be recommended instead. If you insist on using the TPS62560, please change the inductor to the 2.2uH recommended.
  • 0 in reply to Chris Glaser
    Guru 21930 points

    Chris-san,

    Thank you for your response and support.
    I understood about simulation.
    I introduced TLV62080. However,Customers want to use actual devices.

    Customer order to decrease ripple current, using 4.7uH inductor.
    Also,It was the purpose of the inductor current to not to break the 0.

    In the simulation result, it is not in PFM mode.
    TPS62560 sim waveform.pdf
    I would be grateful if you could review the customer circuit phase margin.

    Best Regards,
    Yusuke/Japan Disty





  • 0 in reply to Tsukui Yusuke
    TI__Guru*** 142860 points
    Per the D/S, 4.7uH and 10uF is stable. But stability will change when the customer adds more capacitance to the output bus downstream.

    You can also improve the stability as described here: www.ti.com/.../slva289a.pdf
  • 0 in reply to Chris Glaser
    Guru 21930 points

    Chris-san,

    Thank you for your kind support.
    I will inform customers about the materials you gave me.

    However,Customers can not prepare equipment.
    Therefore, customers need simulation tools or reference values.
    Could you tell me the actual value or simulation correspondence schedule?

    Best Regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Guru*** 142860 points
    Stability will change as output cap is added at the load side. Thus, it does not make sense to simulate/measure the above, but only the final circuit which includes all the components.

    This app note gives a method to determine stability: www.ti.com/.../slva381b.pdf