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TPS769: Minimum Input Voltage

Franz Figueroa32
Intellectual 2660 points
Part Number: TPS769

Hi E2E,

Good day!

We just need some clarification regarding the minimum required input voltage for this part. On page 3, note 2 states that Vin mimum is equal to Vo + Vdo. Vdo values are indicated on page 5. However, on page 4, Note 4 states that the Vin minimum is either 2.7V or Vo + 1V, whichever is higher. Also, note 5 states that if Vo is less than or equal to 1.8V then Vin minimum is 2.7V. Else, if Vo is greater than or equal to 2.5V then Vin minimum is Vo + 1V.

Kindly explain these conditions.Thank you.

Best regards,

Franz

  • 0
    TI__Mastermind 43630 points

    Hi Franz,

    The minimum input voltage is 2.7V.  If you are looking for lower VIN and even lower IQ, we now have the TPS7A24. This works down to 2.4V and has only 2uA of IQ.

    Does this answer your question?

  • 0 in reply to JCHK
    TI__Intellectual 2660 points

    Hi John,

    Thank you for your response.

    Actually, we are looking for the required minimum voltage equation for a given output. There are two equations given on the datasheet. One is on note 2 and one is on note 4. We would like to know which is the correct one. Or if both are correct, on which conditions are those equations applicable?

    Best regards,

    Franz

  • 0 in reply to Franz Figueroa32
    TI__Mastermind 43630 points

    Hi Franz,

    Note 2 is really just saying to make sure you have enough headroom for regulation.  For example, if VOUT is 2.8V, the VDO can be as high as 245mV. So to regulate properly VIN should be VOUT+VDO or 2.8+0.245= 3.045V. 

    Note 4 states clearly that VIN_MIN is 2.7V. But here in contradict note 2 by saying VOUT(TYP)+1V. The reason for this is that any LDO is able to better filter input ripple with more headroom. For example figure 11 shows PSRR with the TPS73933 (3.3VOUT) using 4.3VIN:

    If you do not require VIN up to 10V, the TPS7A20 has a VIN_MIN of 1.6V.

    Does this help to clarify?

  • 0 in reply to JCHK
    TI__Intellectual 2660 points

    Hi John,

    From what I understand, TPS769 will work using the equation on note 2. However, to have a better ripple rejection, it is best to consider the equation on note 4. Is that correct?

    Best regards,

    Franz

  • 0 in reply to Franz Figueroa32
    TI__Mastermind 43630 points

    Hi Franz,

    Yes. That is correct. 

    Regards,