TPS40170-Q1: HDRV pulldown and Enable Timing

Kyle Ryan

Part Number: TPS40170-Q1
Other Parts Discussed in Thread: TPS40170, LM5145

Tool/software:

We are implementing an OVP/UVP circuit on the output of this part and pulling the Hside FET gate low during a fault condition. Is there any harm with loading HDRV (pin17) with a weak pulldown?

The datasheet says min voltage of HDRV is Vsw which is -5V, so I think I am good there. Is there any other issue with this connection (Current output, SW pin, faults)? The sim doesn’t seem to allude to any issues.

Also, I do not see a datasheet time value for Enable/Disable (pin1) to nominal Hside/Lside FET operation, are there any numbers on this? We are considering using this as a backup if disabling the Hside FET option doesn’t work out.

5 months ago

0 Timothy Hegarty 5 months ago

TI__Guru 73652 points

Kyle,

Pulling HDRV directly to GND is not recommended, as it's a high-current gate driver output referenced to SW. Trying disabling by pulling signal pins UVLO or COMP low.

Tim

0 Kyle Ryan 5 months ago in reply to Timothy Hegarty

Prodigy 20 points

Hi Tim,

We wouldn't be pulling HDRV directly to ground, there is a 1k Ohm resistor and the FET Rds in series. It's a high current output for driving FET gates? What if we pulled HDRV to SW instead of GND?

Do you have any time-to-disable data using UVLO or COMP pin?

Kyle

0 Timothy Hegarty 5 months ago in reply to Kyle Ryan

TI__Guru 73652 points

It would be very difficult to overcome the high-current gate driver output. Shorting the gate drive is not recommend. Pulling down UVLO is the way to go and should stop switching immediately.

0 Kyle Ryan 5 months ago in reply to Timothy Hegarty

Prodigy 20 points

Do you have any time-to-disable data using UVLO pin?

+1 Timothy Hegarty 5 months ago in reply to Kyle Ryan

TI__Guru 73652 points

Not readily available, but as it's a comparator input, it should just be the prop delay from UVLO input to gate drive output (< a few µs). You can test the turn-off time on the EVM.

PS: I recommend using the LM5145 over the TPS40170. Same voltage-mode control architecture but a better overall controller at a lower cost.

Regards,

Tim

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TPS40170-Q1: HDRV pulldown and Enable Timing