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TPS65177 HAVDD Duty Cycle limitation and behavior at less than 12Vin

Kevin Wen
Intellectual 2235 points
Other Parts Discussed in Thread: TPS65177

Hi Team,

My customer is evaluating TPS65177 behavior at low input voltage (Vin less than 12V due to cable loss, poor adapter etc). Would you please suggest the maximum duty cycle of Buck 3 (HAVDD) converter in TPS65177? And how does HAVDD behave at low input voltage? For example, if the Vin is 8.6 volt and HAVDD is set at 11V, will this trig the UVP of HAVDD? thanks.

Kevin

  • 0
    TI__Expert 8010 points
    Hello Kevin,

    As a buck converter HAVDD can never get higher than VIN. This means that the given example (VIN = 8.6 V and HAVDD = 11 V) is not possible.
    For VIN = 8.6 V HAVDD can achieve maximum VIN - 0.5 V that means a maximum duty cycle of ~94%. Additionally you have to be aware that the switching frequency will decrease down to ~150 kHz under this conditions.
    What is the programmed HAVDD voltage at your customer? Did they have seen problems with the current setup?

    Thank you.
    Best Regards.
    Ilona