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LM27761: Query regarding LM27761 LDO regulator

Tejashwini R
Prodigy 20 points
Part Number: LM27761

Hi team,

We are working on a new design where the LDO requirement is

Input Voltage : 5V

Output Voltage : -5V

Current : 200mA

And we are planning to use LM27761 LDO regulator.

Since this device is being operated at maximum input(5.5V) and maximum output(-5V), will the output be a stable -5V. Is this approach feasible to get a stable -5V output or Do we need to look for an alternate part for this?

  • 0
    TI__Mastermind 25430 points

    Hi Tejashwini,

    With a 5V Vin, you cannot achieve -5V Vout. This is because you need to compute both the voltage drop from the charge pump’s output impedance (figure 4 d/s) and the LDO drop for the negative output rail. Please consider a different Vout setting. If this is not possible then you may have to look into other devices. But we do not have newer charge pumps that can be used here. Depending on the application requirements, you can use any buck converter by reversing the polarity. But you may have to test it thoroughly before actual implementation. But to be sure, LM2776x is a charge pump with integrated LDOs. Do you need an LDO or Buck converter?

    Regards,

    Febin

  • 0
    Prodigy 20 points

    Hi,

    Sorry for the inconvenience, the input voltage is 5.5V.

  • 0 in reply to Tejashwini R
    TI__Mastermind 25430 points

    Hi Tejashwini,

    With 5.5V input you can achieve -5V Vout. But please ensure that AMR (Vin=5.8V) will not be violated in worst case as well.

    Thanks,

    Febin

  • +1 in reply to Febin
    TI__Mastermind 25430 points

    Hi Tejashwini,

    Do you have further questions? If not, I will go ahead and close this thread. 

    Please hit Resolved if you agree.

    Regards,

    Febin