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UCC28220: conduction time limitation and delay time

Fabio Gou
Expert 4405 points
Part Number: UCC28220

Tool/software:

We used the UCC28220 PWM controller for BB-BOOST control and found that the minimum conduction time was about 270ns, then conduction time couldn't decrease. Is it because this chip has a minimum conduction time limit?

Also, I am looking the curve below. For example, when the junction temperature  increase to Tj=105 ℃, the 0.6V delay suddenly increases to 100ns, and there is no indication above 100ns. Could you please help confirm the maximum delay?

  • 0
    TI__Guru 73345 points

    Hi,

    Based on the data sheet, each pulse starts with CLK set and terminates with CSx + slope after compare to PWM comparator threshold set up by the feedback loop. You need to capture waveforms to find why 270ns min pulse which is affected by your design and operation conditions. For example Vin, inductor value load condition. The IC does not have a purposely setup for minimum pulse.

    CSx have internal shift 0.5V so basically that is why figure you show has vertical change of the delay time. 25C is for typical then at different temperature that shift changes.