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TPS7A8300

Hue Phung
Prodigy 140 points
Other Parts Discussed in Thread: TPS7A8300

Hi,

I would like to use the TPS7A8300 in my new design, I just like to be sure that I will get the lowest drop out voltage possible. The specification indicates that the DOV of this part at 2A is 200mV when Vin > 1.4V, Vbias=open; and DOV=125mV when Vin=1.1, Vbias=5V. From these figures, it seems that the lowest DOV is achieved by having high Vbias.

How can I be sure that I will get the lowest DOV? I can always make  the Vbias=5V, but the input voltage varies between 2 and 3.3V,  how can I ensure that this part  will use the Vbias for the  charge pump and not the input 3.3V? What control the switch for the charge pump?

Thanks

Hue

  • 0
    TI__Guru 55940 points

    Hi Hue,

    You are correct, adding Vbias will improve dropout; however, the improvement is on the order of mV.

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Prodigy 140 points

    Hi Ryan,

    This 75mV difference is very important for me though. I read the datasheet a bit more carefully and it SEEMS to say that if the input voltage is greater than 1.4V, the part will not use the Vbias at all, that is the switch is moved over to select Vin, not Vbias, and as a result I will end up with a higher drop out voltage because my Vin >2V.

    The datasheet does not state categorically if this is really the case, so I can only guess, but I want to be more certain than that, so could you please confirm how the switch in the block diagram work? Is controlled  but the voltage level of the input voltage only?

    Also, if the part does not use Vbias once Vin>1.4V, then I should not be bothered to connect Vbias to the device, this is effectively what the datasheet says, I just like to confirm if this is really the case. Thanks

    Hue Phung

  • 0 in reply to Hue Phung
    TI__Guru 55940 points

    Hi Hue,

    The charge pump is powered by the higher voltage.  Over your conditions, there minimal gain by adding Vbias.

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Prodigy 140 points

    Got it, thanks Ryan.

    Hue