UCC28600: Leading-edge blanking time

Xun

Part Number: UCC28600
Other Parts Discussed in Thread: UCC28700,

Hello team,

Three questions.

1. Is there a minimum Leading-edge blanking time for UCC28600-Q1? This will restrict the minimum turn-on time of the controller, right? Can it go to 0?

2. what is the minimum CS threshold voltage or minimum peak current amplitude that the controller can regulate? For UCC28700 I seethe ratio is about 1/3 as shown in the datasheet.

3. In the excel sheet the calculated switching frequency is higher than 130kHz, as shown below. Is this correct?

Thank you.

over 7 years ago

0 Bernard Keogh over 7 years ago

TI__Genius 9130 points

Xun,

Let me look into these questions and I will get back to you later today or tomorrow.

Thanks,
Bernard

0 Bernard Keogh over 7 years ago in reply to Bernard Keogh

TI__Genius 9130 points

Xun,

1) the UCC28600 does not have internal LEB's. An external RC filter is normally used to get some filtering of any leading edge current-sense spike.

2) The controller can regulate to very low effective CS level, but there is an internal 0.4-V offset. So effectively, the min level will be a little higher than 400 mV.

3) This is a limitation of the Excel sheet, the controller will actually limit to 130 kHz max - if the spreadsheet calculates > 130 kHz, then it will be in burst mode, clamped to 130 kHz. The Mode-Map images tab in the Excel file shows the freq variation vs operating point.

If this answers your question, please click the "verify answer" button.

Thanks,
Bernard

0 Xun over 7 years ago in reply to Bernard Keogh

TI__Mastermind 18120 points

Hi Bernard,

Thanks for the answers. What is the minimum turn-on time of the controller PWM pulse? Is it sth around 100ns?

Regards,

Xun

0 Bernard Keogh over 7 years ago in reply to Xun

TI__Genius 9130 points

Xun,

The minimum on-time will be limited by the prop delay from CS to OUT.

The CS to OUT delay is ~175 ns nom, from the datasheet. But it will be longer if there is an external RC filter on the CS pin.

Thanks,
Bernard

0 Xun over 7 years ago in reply to Bernard Keogh

TI__Mastermind 18120 points

Thanks a lot Bernard

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UCC28600: Leading-edge blanking time