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TPS40170: Low Duty operation

Guru 20090 points
Part Number: TPS40170

Hello,

Could you please let me know the low duty operation of TPS40170?

For example in the condition of Vin=60V, Vout=1V, Iout=7A, fsw=600kHz, the on time will be smaller than minimum controlled pulse.
In this case, is the device skipping the pulse and does the low frequency spectrum occur?

In the webench simulation, the Vswitch is in pulse skip when low duty.

 

Best Regards,
Ryuji

  • The TPS40170 publishes a Ton min of 50ns typical at 60V in, it can be as high as 80ns. If the Ton requirement to regulate the output is lower than this, there will be more energy delivered to the output cap than the output is delivering to the load, then the result will be the output voltage will rise, such that the TPS40170 will start pulse skipping in order to maintain output voltage regulation. You can reduce the switching frequency which will help with this issue. The approx. equation for the min on time is D*(1/FSW), where D = Vout/Vin and Fsw = the Switching frequency.