UCC27712: Must drive MOSFET with 3kHz and sometimes turn it constantly on - how to implement dedicated bias supply for UCC27712?

Karlis Tucs

Part Number: UCC27712

Hi. As already written in thread title I must drive MOSFET with 3kHz and sometimes turn it constantly on. In datasheet it is written that "However, when a dedicated bias supply is used, constant on or constant off conditions can be supported"

What do you recomend to implement dedicated bias supply for UCC27712?

I read that I could use charge pump, but can you please advice how should I change the UCC27712 supply circuitry for this ?

Thanks in advance UCC27712

over 6 years ago

0 Don Dapkus over 6 years ago

TI__Guru**** 189399 points

Hi Karlis,

Thanks for your interest in our products. There are many ways to achieve this. One way is shown in this TI Design:
www.ti.com/.../TIDA-01160

A second way we've done this is shown in Figure 3 of this Users Guide:
www.ti.com/.../snou140a.pdf

Look at the SN6505BDBVR which is used to provide the isolated supply.

Let us know if you have any further questions after reviewing these documents, and we'd be happy to help!

0 Don Dapkus over 6 years ago in reply to Don Dapkus

TI__Guru**** 189399 points

I just noticed another post where my colleague posted a similar solution. See this post:

e2e.ti.com/.../632750

Thanks!

0 Karlis Tucs over 6 years ago in reply to Don Dapkus

Expert 1385 points

Hi Don Dapkus. Thanks for answer. I think I will use this schematic as example e2e.ti.com/.../Visio_2D00_LM27222.pdf .

Can you please advice for how high current should I calculate the floating supply ? I calculated that boost peak current is about 5A for my design. Should I design the floating power supply with average current rating of 5 A?

Best regards,
Karlis Tucs

0 Richard Herring over 6 years ago in reply to Karlis Tucs

TI__Mastermind 21465 points

Hello Karlis,
Thank you for the interest in TI products, I am an applications engineer who works with Don Dapkus. The peak current of the driver will be sourced from the isolated bias supply bypass capacitors. The floating bias supply only needs to supply the average current required for the driver losses and the losses associated with driving the MOSFET gate charge, this will be much lower than the driver peak currents.
In the UCC27712 datasheet typical application section there are equations to determine the various losses of the driver IC and MOSFET gate charge. The total power for the IC and driving the MOSFET are the total of equations 15, 16, 17 and 18. Once the total power is known, the average current is just Pd/VDD. It would be recommended to have margin in the average current capability since the gate charge of the MOSFET can vary as you will see in the MOSFET datasheets..

Regards
Richard Herring

0 Karlis Tucs over 6 years ago in reply to Richard Herring

Expert 1385 points

Ok,thanks for answer.

So I guess I should do just fine with this as floating power supply: https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=8DDF18ED712581A9

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UCC27712: Must drive MOSFET with 3kHz and sometimes turn it constantly on - how to implement dedicated bias supply for UCC27712?