TPS51518: Gate resistor value & linear mode for MOSFET question

Art Mecina

Part Number: TPS51518
Other Parts Discussed in Thread: CSD87352Q5D

Hello Guys,

Good day.

Our customer have the following inquiries on TPS51518.

"For the TPS51518 design using 12V input and a 0.8V output at 12A maximum, 350KHz switching operation, is there any risk of the MOSFET pair CSD87352Q5D device getting into linear mode of operation and this MOSFET pair subsequently heating up and potentially failing? I am asking about increasing the series gate resistors from 0 Ohms to 4.7 Ohms and to 2.2 Ohms, in the upper and lower MOSFET gate signals respectively."

Thanks and regards,

Art

over 2 years ago

0 Matt Schurmann over 2 years ago

TI__Genius 11095 points

Usually it is better to either increase the RBOOT resistor, or include a schottky diode in reverse to prevent slowing the turn-off. It can be questionable to just increase the gate resistor, as the dead time scheme relies on sensing the driver output voltages.

0 Art Mecina over 2 years ago in reply to Matt Schurmann

TI__Genius 16505 points

Thanks for the prompt response Matt. When you refer to the RBOOT resistor, Is it the series passive (sometimes a capacitor) and a diode connected to the input voltage on one side and the switch node on the other?

Thanks and regards,Art

0 Matt Schurmann over 2 years ago in reply to Art Mecina

TI__Genius 11095 points

Hi Art, Yes. The TPS51518 device datasheet has a BST pin showing a capacitor to the SW node pin. You can add a resistor in series with the capacitor to slow the turn-on of the high-side FET without slowing the turn-off.

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TPS51518: Gate resistor value & linear mode for MOSFET question