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TPS61022: datasheet description about pass through mode

Ann_Lien
Genius 14730 points
Part Number: TPS61022


Hello expert,

Base on datasheet description on section 7.3.5 pass through operation, may we know if we need to meet both Vin>Vout and Vout>101% then pass through operation will be enabled? Or we will turn on high side MOSFET when Vout>101%?

Customer has a situation in high temperature reverse current will flow into output capacitance then raise output voltage, but Vin keeps stable. They would like to know if there is chance to turn on high side MOSFET and reverse current will flow through TPS61022. Thanks a lot!

Datasheet description : 

When the input voltage is higher than the setting output voltage, the output voltage is higher than the target

regulation voltage.

When the output voltage is 101% of the setting target voltage, the TPS61022 stops switching

and fully turns on the high-side PMOS FET. The device works in pass-through mode.

Best regards,

Ann Lien

  • 0
    TI__Genius 9046 points

    Hi Ann,

    What is their input voltage and output voltage? Is MODE PFM or FPWM?

    -Wenhao

  • 0 in reply to Wenhao Wu
    TI__Genius 14730 points

    Hello Wenhao,

    input voltage should be 1.8V~2.3V and output voltage should be 3.8V. Thanks!

    Best regards.

    Ann Lien

  • 0 in reply to Ann_Lien
    TI__Genius 9046 points

    Hi Ann,

    I tested this on bench. You case has nothing to do with pass-through mode.

    If you are using PFM, when there is a reverse voltage higher than 3.8V on Vout, there will be no reverse back to Vin side;

    But if you are using FPWM and the reverse current will flow from HSFET back to Vin.

    -Wenhao

  • 0 in reply to Wenhao Wu
    TI__Genius 14730 points

    Hello Wenhao,

    Thanks for your great effort on bench test! Will check with customer, thanks a lot!

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    TI__Genius 14730 points

    Hello Wenhao,

    Customer has other two questions on TPS61022 shown below. May i have your help on it? Thanks a lot!!

    1. how much is the reverse current on high side MOSFET body diode? They would like to estimate the risk when they use FPWM. 

    2. Will reverse current occur in high temperature?

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    TI__Genius 9046 points

    Hi Ann,

    See my comments.

    1. how much is the reverse current on high side MOSFET body diode? They would like to estimate the risk when they use FPWM. 

    [WW]Not sure. The current would not flow from bode diode. Instead it flows through the HSFET and generates heat with I^2*Rds(on). How much current can flow from HSFET depends on reverse strength and input source and is out of TPS61022's control. 

    2. Will reverse current occur in high temperature?

    [WW]if you are using FPWM there will be reverse current flowing from HSFET back to Vin, when Vout>Vout_target, no matter it is high or low temp.

    -Wenhao