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TPS53681: UVLO

Naizeng Wang
Expert 5450 points
Part Number: TPS53681

Hi team,

I have two questions about TPS53681. 

1. Why the UVLO is 4.25V rather than lower voltage such as 3V? What issue will occur when this voltage is much lower?

2. Does the 1.125 mean Vomax=1.125*2.5V=2.8V? Can this ratio be larger? Why?

Br,

naizeng

  • 0
    TI__Expert 5450 points

    Hi team,

    Sorry for the wrong picture. 

    The first picture should be 

  • 0 in reply to Naizeng Wang
    TI__Genius 11095 points

    Hi Naizeng,

    1- The minimum UVLO threshold was defined as 4.25V because the target application for this product is appx 5V to 12V input voltage. TI does not have optimized 3.3V smart power stages, and so it did not make much sense to have a lower UVLO threshold. 

    2- You can use a larger ratio, but TPS53681 only includes internal scaling for up to 1.125. If you use a scale factor which does not match VOUT_SCALE_LOOP/VOUT_SCALE_MONITOR, you will see the READ_VOUT values being scaled in the GUI/PMBus interface. The output voltage is also used to set the correct on-time (DCAP+ behaves like a constant on time controller), and you may also see the switching frequency get scaled. However, TPS53681 also has a frequency correction control loop, which may be able to compensate for the frequency change within about ~30-40%.