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LP5900: Regulation at dropout voltage less than 1 V

Mikhail Matusov
Intellectual 340 points
Part Number: LP5900

The datasheet says that at least 1 V dropout voltage is required for achieving good regulation, however the minimum dropout voltage is a lot less. How bad the regulation will be with let's say Vin=Vout + 0.5V? Thanks.

  • 0
    TI__Genius 12345 points

    Hi Mikhail, 

    The LP5900 device will regulate with 0.5V of headroom. 

    The device was tested with Vin=Vout+1V, therefore, the EC table shows specs with such condition, unless otherwise noted.

    The device is capable of regulating with 150mV of headroom, however, PSRR and other of its dynamic performance will be impacted by this, therefore, having a recommendation of 1V of headroom is given. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    Intellectual 340 points

    I appreciate your answer but 1 V dropout is a strange choice for testing an LDO, which is supposed to work down to 150 mV. I am sure your customers would like to see some plots showing how various parameters are affected by running with lower dropout voltages. Thanks.

  • +1 in reply to Mikhail Matusov
    TI__Genius 12345 points

    Hi Mikhail, 

    It was a common practice to use 1V of headroom even for LDOs. As already mentioned, PSRR is one of the affected specs.

    We do show plots to showcase this, as an example:

    Notice that Vin-Vout=0.5V, and there is some degradation in lower frequencies. 

    Best, 

    Edgar Acosta