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Original question:

TPS723: TPS723 feedback resistor range

TPS723: Positive LDO from the same series

Selvedin Hodzic
Prodigy 210 points
Part Number: TPS723
Other Parts Discussed in Thread: OPA855, , TPS7A39, TPS730, LP2992

Hello together,

I would like to supply the operational amplifier OPA855 with ±2.5 V. I wanted to use two LDOs (positive and negative separated).There is a switching regulator before the LDOs. The output voltage of the switching regulator is ±3.3 V. Using LDOs I bring this voltage to ±2.5 V. I have chosen a negative liner regulator.

The series is TPS723. Now I need a positive one from the same series. Can you suggest one that I can combine with TPS723 to power the OPA855?

Kind Regards

Selvedin Hodzic

  • 0
    TI__Mastermind 47300 points

    Hi Selvedin,

    The LP2992 might be a good compliment to the TPS723.  However, a few years ago we did release the TPS7A39 which is a dual +/- LDO with a startup tracking feature. This makes it so both rails come up simultaneously. 

    I hope this works for you.

  • 0 in reply to JCHK
    Prodigy 210 points

    Hi John,

    Thanks for your suggestion and other information. TPS7A39 is also good but is problematic for me because of the package(WSON(10). Pins are difficult to solder by hand. 

    Would TPS730 also be a good choice in combination with TPS723?

    If I now wire these two LDOs TPS723 and LP2992 with OPA855,  are there limitations regarding the operational amplifier?. It has an output current of ±100mA. Can you explain me how the output current of the LDO and the output current of the operational amplifier are related?

    Best Regards

    Selvedin Hodzic

  • 0 in reply to Selvedin Hodzic
    TI__Mastermind 47300 points

    HI Selvedin,

    The TPS730 is another choice that can work well. 

    The Positive LDO can only source current and the negative LDO can only sink current. So as long as the absolute maximum voltage across the operational amplifier is not exceeded, the LDO's only need to be sized such that that can support the maximum output current+ the maximum Iq of the device. For the OPA855 this looks like 100mA+19.5mA or ~120mA.

    I hope this answers your question. If you need more details on the OP-amp, please post your question to the high-speed Op-amp forum.

  • 0 in reply to JCHK
    Prodigy 210 points

    Hi John,

    Thank you  for your kindly support!

    Kind Regards

    Selvedin Hodzic