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TLV70033EVM-503: Trying to decide between TLV70033DDCR and TLV70032DDCR

Daniel Rhodes
Prodigy 70 points
Part Number: TLV70033EVM-503
Other Parts Discussed in Thread: TLV700

Tool/software:

Our optical sensor manufacturer recommends using LDO to filter each power rail.  Unfortunately our sensor board only has 3.3V available and the sensor requires 3.2V to 3.4V for this supply.  Does it make more sense to use the 3.2V LDO for a guaranteed output at under 100mA or use the 3.3V regulator and assume about 50mV drop giving me 3.25V.  I would prefer the higher voltage as it's more in line with the operational voltage the sensor is specified for.

  • 0
    TI__Expert 6370 points

    Hi Daniel,

    Given that the output accuracy is ±2%, a 3.3V output would make more sense since the output deviation would be ±66mV in the worst case. This would allow the output voltage to remain within the limits of 3.2V to 3.4V.

    Regards,

    Andres 

  • 0 in reply to Andres Sagredo
    Prodigy 70 points

    When running the 3.3V LDO with a 3.3V input, will it still provide the high PSRR from the spec sheet even though it is out of regulation?  An LDO is recommended by the sensor manufacturer for the power supply filtering, otherwise we would just use the 3.3V directly.

  • 0 in reply to Daniel Rhodes
    TI__Expert 6370 points

    Hi Daniel,

    My mistake, I misunderstood the issue here. The input voltage is 3.3V and the load also requires 3.3V, correct?

    If this is the case, then an LDO will not be feasible given that there needs to be a difference between Vin and Vout, also known as dropout. If there is a way to increase the input voltage to meet the condition dropout < Vin - Vout, then it would be possible to use TLV700, which has a dropout of 175mV at full load.

    Regards,

    Andres

  • 0 in reply to Andres Sagredo
    Prodigy 70 points

    Perhaps the TPS73101DBVR set for 3.24V might work?

  • +1 in reply to Daniel Rhodes
    TI__Expert 6370 points

    Hi Daniel,

    The dropout spec is very tight for TPS73101DBVR, probably setting the output voltage a littler higher to roughly 3.25V would be better to account for the accuracy as well. Given how tight this output voltage will be, it is recommended to use resistors with good tolerance and to follow the recommendations in the datasheet:

    Regards,

    Andres