From Worst Case Analysis Analyst :
The TPS50601 datasheet specifies a typical minimum-off time of 500ns with no tolerances. Therefore, we assumed that the tolerances specified for the minimum on-time were also applicable to the off-time.
The typical minimum on-time specified in the TI TPS50601 datasheet is 101ns. The MIL-SPEC specifies a maximum of 175ns at 25C. Lastly, the datasheet specifies a typical of 127ns at 80 deg C.
We normalized these tolerances and assumed they also applied to the 500ns typical minimum off-time. The result of this process is the 995.05ns worst-case minimum off-time.
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I am wondering when it would actually be applicable to apply a worst-case specification on the minimum off time. This depends on duty-cycle and PVin. Setting PVin to 3V and a duty cycle of 85% as specified by the WebBench tools and 3.3V input and 2.5V output is non-complaint by a wide margin at our switching frequency (340kHz). It would require a switching frequency of 145kHz in order to achieve this T-off min time.
PVin=Vin=3.0V
Switching Freq = 376KHz
Vin = 3.3V
Vout = 2.5V
Duty Cycle = ~85% (WebBench).
I am trying to collect some more datapoints on the operation of the regulator so I can go back to the analyst and discuss whether the min-time off would apply to our design.
Do you have a graph of time-off min vs temperature?
Does the oscillator frequency equal the switching frequency of the output?
