UCC21540-Q1: Being used when the frequency is very low

Albert Wang1

Part Number: UCC21540-Q1

Can this chip be used in the situation that the frequnency is very low? For example, this chip should control the high side mosfet and the low side mosfet both being ON for more than 60 seconds. At this period, these mosfets won't be turned off. In this situation, can the bootstrap capacitor provide enough energy on VDD without charging?

over 4 years ago

0 Don Dapkus over 4 years ago

TI__Guru**** 189401 points

Hi, Albert,

Welcome to e2e, and thanks for your interest in our products.

Your doubt is correct, the bootstrap cap would be unrealistically large to support such long on-times for the high-side.

Is it ok to email you directly to understand your application so we can make the most appropriate suggestion for you?

0 Albert Wang1 over 4 years ago in reply to Don Dapkus

Prodigy 40 points

Hello, Don

Thank you very much for your explanation.

If this chip can not work in this situation, maybe i should try other methods to realize the clamping function.

By the way, what is the minimum frequency for this chip? Just for reference.

0 Wei Zhang over 4 years ago in reply to Albert Wang1

TI__Intellectual 2061 points

Albert, There is no minimum fs. You can drive DC for the input as long as you have all the biases above UVLO.

0 Albert Wang1 over 4 years ago in reply to Wei Zhang

Prodigy 40 points

Hello, Wei

Thank you very much for your information!

But in my comprehension, the chip need the bootstrap cap to provide energy to maintain the voltage in high side drive route. The cap need to be charged when the low side turned on according to the manual. But the bootstrap cap maybe too large if we need the chip working in a very low frequency.

So maybe this chip isn't capable to work in a very low frequency.

0 Don Dapkus over 4 years ago in reply to Albert Wang1

TI__Guru**** 189401 points

Hi, Albert, I have some examples I can send you via email. Is it ok to send them to the email address registered to your my.ti.com account?

0 Albert Wang1 over 4 years ago in reply to Don Dapkus

Prodigy 40 points

Hello, Don

Yes, of cource it is OK.

Thank you very much for your support!

0 Don Dapkus over 4 years ago in reply to Albert Wang1

TI__Guru**** 189401 points

Thanks, Albert! I'll email you right now.

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UCC21540-Q1: Being used when the frequency is very low