UCC28740: Question regarding CS, Ipp (min)

Xiaoying Lu

Expert 4270 points

Part Number: UCC28740

Hi team,

There is a description in the datasheet that the minimum current-sense threshold (VCST(min)) is 0.194 V for IPP(min).

Can you help explain more about the details? What will happen if it is lower than 0.194V?

Regards,

Xiaoying

over 1 year ago

0 Manuel Alva Hernandez over 1 year ago

TI__Genius 15536 points

Hi Xiaoying,

VCST is the output of the Control Law block (see Block Diagram below). It goes from a minimum value (VCSTmin) to a maximum value (VCSTmax) depending on the load conditions. At no load or light load, Vcs voltage should be higher than VCSTmin and at full load Vcs voltage should be lower than VCSTmax. If current sense resistor Rcs was designed for an overcurrent condition (CC mode), Vcs voltage should be in that range.

Thank you.

0 Xiaoying Lu over 1 year ago in reply to Manuel Alva Hernandez

TI__Expert 4270 points

Hi Manuel,

Thanks for your reply. Can I know what will happen if Vcs voltage is lower than the minimum value (VCSTmin)? Can you explain more details?

Xiaoying

+1 Manuel Alva Hernandez over 1 year ago in reply to Xiaoying Lu

TI__Genius 15536 points

If Vcs voltage is lower than VCSTmin, the IC will never command pulses at the DRV signal. Meaning 0% duty cycle. This event means that the feedback current is greater than 35uA at no load (see below), which is uncommon to happen.

Thank you.

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UCC28740: Question regarding CS, Ipp (min)