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TPS7A57: Charge pump or BIAS?

Kei Kuwahara
Expert 8160 points
Part Number: TPS7A57


Tool/software:

Hello team,

I am getting confused looking at the Typical Circuit of TPS7A57, which is placed on 1st page of the datasheet.

For this circuit, BIAS is supplied with 5V, but at the same time, internal charge pump is also enabled.
My understanding is we don't need charge pump, because BIAS is supplied externally.

Which will source the power supply for this configuration, BIAS rail or internal charge pump?
Is there any advantages by supplying BIAS and enabling charge pump at the same time?

Best Regards,
Kei Kuwahara

  • +1
    TI__Guru 50025 points

    Hi Kei,

    I believe the information you are looking for is in Section 7.3.5:

    In the circuit diagram you mentioned VIN is 0.9V < 1.1V, and so BIAS is required and supplies the internal biasing current, and the charge pump can be enabled or disabled. This implies that the charge pump doesn't supply any current in this scenario. Even though the charge pump doesn't supply current in this scenario there will still be some switching noise, so it would be best to disable the charge pump in this case. This diagram represents the case that the switching noise can be tolerated in the system and so the charge pump is left enabled. 

    Regards,

    Nick