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TPS62615: Use Feedback network to push Vout to 1.26V on TPS62615

Sebastian Wissig
Prodigy 70 points
Part Number: TPS62615
Other Parts Discussed in Thread: TPS62801

Hello,

is it possible to push the output voltage with a feedback network to 1.26V? The input resistance of the Pin is 480 kOhm (or 2.5 µA).

So it should be possible to have a resistor feedback in the 10-kOhm range to manipulate the feedback voltage.

Can you please confirm?!

Best regards

Sebastian Wissig

  • 0
    TI__Expert 5425 points
    Sebastian,

    in theory this may work. Unfortunately the internal resistors are not very accurate regarding absolute value, just the resistor ratio is accurate. This means it will be very hard to get a circuit which is reliable in production. We have devices with different fixed output voltages in this family. e.g. TPS62617 (Vout 1.3V). I would guess this would be more accurate although the nominal value is +3% off.

    Best regards,
    Juergen
  • 0 in reply to Juergen
    Prodigy 70 points

    Hello Juergen,

    the TPS62617 is not widely available.  I already considered that the resistors inside the package are accurate in ratio, but not in absolute value. That is the reason why I have chosen the feedback network with low value resistors (see picture below). The resistance seen from the FB pin is roughly 1 kOhm. So if the internal network in the IC (specified with 480 kOhm) should not make any difference.

    Best regards

  • 0 in reply to Sebastian Wissig
    TI__Expert 5425 points
    Hello Sebastian,

    Your picture did not come through. I guess you just add an external low impedance feedback divider using the 1.2V as a reference/FB voltage. I don't see a technical reason why this should not work with this device. It is not TI's recommended way of using the device, of course.

    Another option for your circuit could be using the new TPS62801. The device can be set to a fixed output voltage of 1.25V and it should be available.

    Best regards,
    Juergen
  • 0 in reply to Juergen
    Prodigy 70 points
    Yes, did also look into the TPS62801. Lets say there are other drawback...

    I will stick with the low impedance resistor divider, even if it is not recommended by TI. When the 1.3V version becomes widely available I can use that one as a drop in replacement.

    Thank you for your support
    Sebastian