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LM27761: Effect on TLV4170 op-amp

Aditya Teja Damera1
Prodigy 120 points
Part Number: LM27761
Other Parts Discussed in Thread: TLV4170

Hi,

We are planning to supply the op-amp TLV4170 negative supply with the LM27761 to generate at -5V.

As we are using the Op-amp for ADC channels which are very sensitive to noise, will the LM27761 circuit cause any issue due to its high frequency (2 MHz) operation?

One of the main concern is the PSRR of TLV4170. We don't want to change the TLV4170 for this design.

Please suggest.

  • 0
    TI__Mastermind 34201 points

    Hi Aditya,

    I'm check internally and get back to you immediately.

    Best regards,

    Excel

  • 0
    Guru 298340 points

    A higher switching frequency actually results in a lower output ripple:

    You can reduce the ripple further by enlarging the output capacitor.

  • 0 in reply to Clemens Ladisch
    Prodigy 120 points

    Hi Clemens,

    Thanks for the reply. Yes. Higher the frequency, lower is the ripple. But our concern is that will the higher frequency operation effect the op-amps TLV4170?

    We thinking to add an LC post filter. What do you suggest, will it help? 

    Please confirm if TLV4170 will be effected by this high frequency operating LM27761 output.

    Thanks,

    Aditya Teja

  • 0 in reply to Aditya Teja Damera1
    Guru 298340 points

    The effect of the power supply on the opamp output is measured by the power-supply rejection ratio:

    Having half the noise at double the frequency might not make a difference by itself. But when the noise frequency is further away from your signal, it is easier to filter out.