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TPS61089: Vin near to Vout behavior

Daria Kiseleva
Intellectual 2755 points
Part Number: TPS61089

Hello colleagues,

I am going to hold up a display backlight supply voltage during pulses. The main 12V will start to drop down and the only one deactivating will be the display internal backlight driver circuit leading to flicker.

TPS61089 working as a boost DCDC with the output voltage quite similar to the 12V rail nominal voltage. How is this chip going to act if I set this one to 11V for example so that it will be (nearly) invisible during the normal operation but will go to regulation in case of a drop. Is this possible? (stable running at lowest Fsw in PFM for example or stopping switching and just bypass)

Thanks,

Daria

  • 0
    TI__Genius 16325 points

    Hi Daria,

    I'm not quite understand about the display backlight situation.

    But I'm wonder that you are asking about what TPS61089 act when output voltage is 12V and its target output voltage is 11V.

    For TPS61089, when Vout is higher than target, it will shut down both low side and high side switches and waiting for voltage to drop.

    the body diode of high side mos will conduct and current can flow through the diode from input to output.

    Please be noted the device will work in 'large ripple mode' when Vin is sightly lower than Vout. Please refer to below answer.

    (+) TPS61089: ripple @ below conditions - Power management - INTERNAL forum - Power management - INTERNAL - TI E2E support forums

    So, it will be ok to use TPS61089 from another source like 5V to transfer to 11V as a backup of 12V,

    but not a good solution for an input from 5 to 12V boost to 12V.

    I hope the answer can help.

    Best Regards

    Fergus