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TPS543C20A: Cramp value, transfer characteristics

Part Number: TPS543C20A

Hello team,

TPS543C20A's control mode is ACM and we can select Cramp for better performance.

How does Cramp value affect loop transfer characteristics? Will the Ramp signal affect output ripple on current? or voltage? in terms of transfer characteristics.

Could you let me know any material which explains ACM transfer characteristics, if you have?

Best regards,

  • Hello,

    Increasing the RAMP resistance and ramp capacitance will increase the gain, crossover frequency, and bandwidth of the the converter's control loop. This will typically improve peak-to-peak transient performance. However, the RAMP selection must take into account the sacrifice in gain margin and phase margin that a larger bandwidth provides, so a higher RAMP setting will not always guarantee stability.

    The RAMP selection will not impact output ripple current or voltage in a static mode analysis assuming the device is stable.

    Regards,

    Alec Biesterfeld

  • Hello Alec-san,

    Thank you for your comment.

    In my customer case, there is a case that load is not a simple capacitor load, and concern the stability with the case. So they concern that selecting the value from load capacitor type may not work in the case. Therefore it is preferable for customer that they understand ACM transfer characteristics.

    Do you have any good application note or training material for ACM control?

    Best regards,

  • Hi Taketo-san,

    I recommend using WebBench to simulate the design as a first step in designing with the TPS543C20A. The Webench model will provide a good idea of how the customer's design may perform as it relates to load transient and frequency domain stability.

    Unfortunately, a lot of the good app notes for ACM are works in progress at the moment and have not been released on the ti.com. 

    Please email me at a-biesterfeld@ti.com and I would be happy to provide documentation to you to support the customer's design.

    Sincerely,

    Alec Biesterfeld