I used Switcher Pro and the TPS40210 switcher to design a circuit. I noticed the foot note indicating the " Duty cycle is too low for the device in this situation. Calculated on time is below the minimum controlllable on time of the device! " From the analysis data the design has a switching freq of 700 khz and the device has a minimum controllable on time of 400ns.
What do I need to do to increase the duty cycle?
Thank you,
Hello Keith
OnTime is calculated in the Analysis page under the "Output Tab" it's at the bottom. If that goes below the minimum on time of the device then you will get this warning. For your case you can calcualte that minimum duty cycle like this
400ns * 700kHz = 28% duty
if in your analysis /output tab/ duty cycle min field you have something less than 28% it's going to get flagged as a possible issue.
Don't forget that Duty is more than just Ideal vout/vin = 1/(1-D)
we're using a more accurate method like this
I hope this helps!
