UCC28950

Dimit Ariti

Other Parts Discussed in Thread: UCC28950

I’m using UCC28950 to implement a 2.1 kW phase shifted full bridge dc/dc converter. Since the output voltage is high 170V I’m not using synchronous switch instead I’m using ultra fast diodes. No the question is that should I just leave the OUTE and OUTF pin float and N/C? Or should I connect the DCM pin to VREF to cheat the UCC28950 so that it assumes it’s always in DCM mode and so not generating any OUTE or OUTF signal. Or should I connect DCM pin to GND?

Thanks

over 9 years ago

0 Oliver Pan91 over 9 years ago

TI__Intellectual 2230 points

Hi Mosi,

Please just connect the DCM pin to VREF to shuts both outputs OUTE and OUTF if you don't need synchronous rectification.

Thanks
Oliver

0 Dimit Ariti over 9 years ago in reply to Oliver Pan91

Prodigy 110 points

What about other pins related to OUTE and OUTF like ADELEF and DELEF? should I just let them to be float and N/C similar to OUTE and OUTF pins?

0 Colin Gillmor over 9 years ago in reply to Dimit Ariti

TI__Mastermind 25570 points

Hi Mosi

In general it's not a good idea to allow pins to 'float' unless the IC datasheet specifically allows it.

In your case, I would recommend that you tie the ADELEF pin to ground and that you connect the DELEF pin to GND through a resistor. In fact any resistor in the allowed range of 13k to 90k would do (page 20 of the data sheet), but I prefer to keep the impedances low so I'd use a value near the lower limit, say 15k Ohm.

Regards

Colin

0 Colin Gillmor over 9 years ago in reply to Colin Gillmor

TI__Mastermind 25570 points

Oh and BTW, Leaving the OUTE and OUTF outputs floating IS ok in this case. They are driver outputs and are tied LOW internally when deactivated.

Regards
Colin

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UCC28950