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TPS61022: Enable with Vin == 0.5V && Vout == 3.3V?

Bill Gray
Prodigy 30 points
Part Number: TPS61022
Other Parts Discussed in Thread: TIDA-050039,

My current project needs to boost a single cell PV panel @ 0.5-0.6v to charge a Li Ion battery @ 4.2v.  The PV will be coming on and off line with the daily solar cycle.

In this application, Vout will never drop below 3.3v.  But in the early morning Vin < 0.2v and will rise to 0.5-0.6v.

Will the TPS61022 turn in this situation?  The datasheet feels a bit ambiguous on this point.

Thank you,

Bill

  • 0
    TI__Mastermind 34231 points

    Hi Bill,

    TPS61022 needs a 1.8V rising UVLO minimum and falling UVLO threshold is 0.5V. So cannot be used for this application.

    The TI design TIDA-050039 may fit for your application, please take a look at it: http://www.ti.com/lit/ug/tiduew2/tiduew2.pdf?ts=1591235756820

  • 0 in reply to Zack Liu
    Prodigy 30 points

    Zack,

    Thanks for your response.  I read the Application Note you linked thoroughly.  Then I read and re-read the spec sheets to see if my thinking on this issue was flawed, and I found that the spec sheets were a bit ambiguous, but seemed to indicate that Vout > 2.2v would negate the need for rising 1.8v on Vin to overcome the UVLO.

    So I bought a TPS61022EVM-034 Evaluation module to test this idea in hardware.

    Turns out that I was correct.  The TPS61022 will turn on if Vout and EN are held above 2.2 with a Vin voltage of 0.6 volts.  In other words, a 1.8v rising on Vin is not required for turn on if Vout is held above 2.2v.

    Bill

     

  • 0 in reply to Bill Gray
    TI__Mastermind 34231 points

    Hi Bill,

    TPS61022 Vin pin rising UVLO threshold is 1.8V (Vout = 0V), which means the device starts regulating the Vout. When Vout > 2.2V, the device could keep working until Vin votlage drops to 0.5V. 0.5V is the falling threshold spec when Vout > 2.2V.

    However, the datasheet never says the rising UVLO threshold is 0.5V with a 2.2V voltage pre-biased at Vout. Actually this device rising UVLO threshold is around 1.55V with 2.2V pre-biased at Vout (This is not list in datasheet)

    To verify it, use a 2.2V DC source pre-biased at Vout pin, then increase the input voltage and see when the SW pin starts switching.