Isolated Gate driver Required

Hi Aneesh,

Thank you for your question. I work on the applications team in the high power drivers group.

1. Do you need safety isolation? Do you need reinforced or basic? What creepage and clearance?
2. Do you need just a high-side driver, or a high-side and low-side driver?
3. Is the half-bridge switching up to 500V, or is it just going across the 500V domain?
4. Can you please share the MOSFET part number? You cannot switch 400V using 60V MOSFETs.

UCC21540 and UCC21222 are dual-channel isolated gate drivers which might be able to work for you, but I’ll need more information to be sure.

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Thanks and best regards,

John

Hi Aneesh,

Thanks for getting back to me with this information.

1. It sounds like a driver like UCC21222 or UCC21220 will have the correct isolation voltage for this application. This driver has 4mm input-to-output creepage, and 2mm ch-ch creepage. If higher isolation or larger creepage/clearance is needed, UCC21540DWK will be the correct option.
2. The two previously mentioned drivers are dual-channel and can be configured to drive high-side and low-side FETs as a half-bridge driver. These drivers are able to support a 400V half-bridge, since both CHA and CHB are functionally isolated from each other and have 2mm creepage from channel to channel.
3. Understood. UCC21222, UCC21220, and UCC21540 can all operate as half-bridge drivers with 400V bus.
4. Thanks for sharing. Understood on the configuration of input and output voltage. Feel free to check out this reference design, since it sounds similar to what you are doing.
   1. http://www.ti.com/tool/TIDA-010062

If this helped answer your question, could you please press the green button? If not, feel free to ask more questions.

Thanks and best regards,

John

Hi Aneesh,

1. You can still use this chip if you put a voltage divider circuit between the controller and the input. Another option is to use UCC21520, which can accept up to 18V inputs.
2. Driver source and sink current are usually tuned to switch MOSFETs as fast as possible while still meeting EMI standards. With higher sink/source current, you will switch the MOSFETs faster and increase efficiency. Output drive strength is limited by selection of gate resistors as well. Feel free to read through this tech note on gate resistors.
   1. http://www.ti.com/lit/an/slla385/slla385.pdf

If this helped answer your question, could you please press the green button? If not, feel free to ask more questions.

Thanks and best regards,

John

Hi Aneesh,

I think you’re talking about the input rise time, correct? I don’t think that resistors in the 5k-10kOhm range will slow down your input signal too much, especially if they are driven from the gate drive output of your controller and will have similar capacitance values.

You can use this resistor calculator to determine a resistor divider value that will work for you.

http://www.ti.com/download/kbase/volt/volt_div3.htm

I also put together a quick figure showing some of the divider values on the INA pin when I put a 12V to 3.3V divider into the calculator.

If this helped answer your question, could you please press the green button? If not, feel free to ask more questions.

Thanks and best regards,

John                                                                                                                                                                                  

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