DRV8303: FET Reverse Polarity Protection

Michael Bauer2

Part Number: DRV8303

Can the DRV 8303 be used to turn on a N Channel FET with the source connect to power in and the the drain connected to PVDD od the DRV8303? I want to used the FET for reverse polarity protection. Can the trickle charge circuit turn on the FET channel and bypassed the substrate diode to reduce the voltage drop?

over 6 years ago

0 Adam Sidelsky over 6 years ago

TI__Guru 65190 points

Michael,

Please show a schematic of what you are proposing.

We suggest a circuit like the following to most customers: http://www.ti.com/lit/ds/symlink/drv8343-q1.pdf Section "8.3.5.10 Reverse Supply Protection"

Regards,

-Adam

0 Michael Bauer2 over 6 years ago in reply to Adam Sidelsky

Prodigy 190 points

Can the trickle charge circuit charge up the bootstrap cap when the source of the high side FET is

connected to the input power. The driver chip will be powered though the substrate diode until

the channel is turned on. I will also probably add a 10K series gate resistor and the proposed

transistor shutdown circuit.

0 Adam Sidelsky over 6 years ago in reply to Michael Bauer2

TI__Guru 65190 points

Michael,

The BST caps can only charge once the LS FETs turn on. Even if the GVDD supply which feeds the BST caps is active once the PVDD is up, the current path for charging the BST caps is dependent on the Switch node (SHx) goes low.

Why do you have "Power IN" marked on the SHA output above?

Regards,

-Adam

0 Adam Sidelsky over 6 years ago in reply to Adam Sidelsky

TI__Guru 65190 points

Michael,

I misunderstood previously. To clarify, no there is no way for the trickle charge pump to operate if power is applied to the HS Source. Power should not be applied here.

Regards,

-Adam

0 Michael Bauer2 over 6 years ago in reply to Adam Sidelsky

Prodigy 190 points

The POWER IN is the same as Vbat in DRV8343 8.3.5.10 Reverse Supply Protection. I know the bootstrap capacitor is normal charge when the low side of the bridge is turned on, but there is a trickle charge circuit in the driver chip that can maintain gate power ever at 100% on time. My question is can the internal trickle charge circuit in the driver chip turn on the reverse polarity FET. The bootstrap capacitor could probably be much smaller or not needed at all.

0 Adam Sidelsky over 6 years ago in reply to Michael Bauer2

TI__Guru 65190 points

Michael,

This is not the case, the power in is PVDD, not SHA. There is no method by which the Trickle charge pump can operate unless the PVDD supply is present.

Regards,

-Adam

0 Michael Bauer2 over 6 years ago in reply to Adam Sidelsky

Prodigy 190 points

Adam

When Vbat of the correct polarity is applied to the circuit, power will be applied to PVDD though the substrate diode of the reverse polarity protection FET. The SHA pin will also receive power and it will be one diode drop above the PVDD until the FET channel is turned on. When the FET is on SHA will be at the same potential PVDD, just like the high side FET in a half bridge configuration.

0 Adam Sidelsky over 6 years ago in reply to Michael Bauer2

TI__Guru 65190 points

Michael,

Looking at this again, I think I understand. You want to use only two phases, not a three-phase motor. You are asking if the phase A high-side FET can be used as the reverse polarity protection FET. This assumes you're not using the phase A low side.

If this is true and you use the circuit as you included previously, also reattached here, then this should work.

If you do this, please GND the SL_A pin and keep the gate floating.

Regards,

-Adam

0 Michael Bauer2 over 6 years ago in reply to Adam Sidelsky

Prodigy 190 points

I think I got it. Here is another view.

thanks or the help

mike

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DRV8303: FET Reverse Polarity Protection