TPS23757: The second gate drive by GAT2

tateo yamashiro

Part Number: TPS23757

Hi,

We got a question from the customer about GAT2 circuit on TPS23757EVM.
Could you help us?

[Question]
- How can we determine C22, C23, R18 and R19? What is these components used for?
- If we need to be faster turn-on time, which components should we modify?

Best Regards,
tateo

over 6 years ago

0 Darwin Fernandez over 6 years ago

TI__Mastermind 40120 points

Hi Yamashiro-san,

This is described more in detail in the below TI seminar paper.
www.ti.com/.../slup262.pdf

If needing a fast turn ON, I recommend a choosing a FET with lower gate capacitance/charge

0 tateo yamashiro over 6 years ago in reply to Darwin Fernandez

Guru 10890 points

Hi, Thank you for your quick reply. Your material is very helpful. Could you tell us about additional things?

- How can we determine C23 and R19? What is these components used for?
- Can we adjust the turn-on time by this circuit?(R14 is used for a gate resistor?)

Best Regards,
tateo

0 tateo yamashiro over 6 years ago in reply to Darwin Fernandez

Guru 10890 points

Hi, Are there any update on that? We would appreciate it if you could give us your feedback.

Best Regards,

tateo

0 Darwin Fernandez over 6 years ago in reply to tateo yamashiro

TI__Mastermind 40120 points

Hi Yamashiro-san,

C23 should be large enough to have a clean PWM signal to drive the synch FET. We have seen it go low as 0.1uF. It is not recommended to increase it further (for lower impedance) as it must discharge fully during shutdown (R19 is used to aid with this discharge quicker).

0 tateo yamashiro over 6 years ago in reply to Darwin Fernandez

Guru 10890 points

Hi, Thank you for your support. Sorry for bother you again. We want to make sure about R14. Is this the gate resistor? If this adjusted to large value, does the turn-on time become slow?

Best Regards,
tateo

0 Darwin Fernandez over 6 years ago in reply to tateo yamashiro

TI__Mastermind 40120 points

Hi Yamashiro-san,

That's correct, R14 is the gate resistor, since it's set to 0 ohms, there is no slowing down with the FET's gate capacitance. If increased, yes it will slow down the turn ON of the FET.

Regards,

Darwin

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TPS23757: The second gate drive by GAT2