TPS25983: Vbr on CdV/dt Protection Diode

John Westmoreland

Prodigy 160 points

Part Number: TPS25983

Tool/software:

Hello All,

What is the Vbr - reverse breakdown voltage on the internal CdV/dt pin (see in attached image).

Thanks,
John

7 months ago

0 Arush Gupta 7 months ago

TI__Mastermind 38985 points

Hi John,

This is a Schottky diode so the breakdown voltage will be very high. I don't have exact value. How much voltage are you applying?

Best Regards,
Arush

0 John Westmoreland 7 months ago in reply to Arush Gupta

Prodigy 160 points

Arush,

The charge pump is taking it close to 29 or so volts wrt ground. Note the power transistor I'm using on the output has Vgs +/- 20V - using the same one that's in the EVM basically - I'm wondering if the charge pump can take that too high if I make the C dV/dt capacitor too large - say 1 uF. I have seen some parts fail - I'm going to try and figure out what the failure mechanism is. I have figured out a way to use this with large (load) capacitances (handling large inrush currents) - but I'm not going to post that solution here.

Thanks,
John

0 John Westmoreland 7 months ago in reply to John Westmoreland

Prodigy 160 points

I should add the picture of the diode is for a plane jane silicon rectifier - not a Schottky. Maybe update that?

0 Arush Gupta 7 months ago in reply to John Westmoreland

TI__Mastermind 38985 points

Hi John,

Arush Gupta said:
This is a Schottky diode so the breakdown voltage will be very high. I don't have exact value. How much voltage are you applying?

Let me double confirm this with the design team. Anyways the charge pump will be at high voltage so apply reverse voltage for breakdown will not happen.

Best Regards,
Arush

0 Arush Gupta 7 months ago in reply to Arush Gupta

TI__Mastermind 38985 points

Hi John,

I double checked this. The diode is pn junction diode and reverse breakdown voltage is around 8-10V.

Best Regards,
Arush

0 John Westmoreland 7 months ago in reply to Arush Gupta

Prodigy 160 points

Arush,

I've been using the TPS25983 in a 24V design. Is that 8-10V wrt ground or wrt to the transistor source?

If I put a 1uF capacitor; for instance - for the capacitor connected to Pin 15 - is it possible to charge higher than the Vbr of that diode? To be safe(r) maybe an external diode with a higher Vbr should be put on Pin 15?

Thanks,
John

0 Arush Gupta 7 months ago in reply to John Westmoreland

TI__Mastermind 38985 points

Hi John,

This is reverse breakdown voltage of diode which you pointed out in functional block diagram. The other end of this diode is connected to the HFET gate.

John Westmoreland said:
If I put a 1uF capacitor; for instance - for the capacitor connected to Pin 15 - is it possible to charge higher than the Vbr of that diode? To be safe(r) maybe an external diode with a higher Vbr should be put on Pin 15?

If you are not intentionally pushing higher voltage at this pin, then the voltage will definitely not rise to high enough level to cause diode reverse breakdown. The other end of diode should be at around 29V.

Best Regards,
Arush

0 John Westmoreland 7 months ago in reply to Arush Gupta

Prodigy 160 points

Arush,

So, the Vbr of this diode is wrt the source of the external transistor; correct?

Thanks,
John

0 Arush Gupta 7 months ago in reply to John Westmoreland

TI__Mastermind 38985 points

John,

No, diode is between the gate of internal FET and dvdt pin. You connect dvdt pin to gate of external FET.

Best Regards,
Arush

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TPS25983: Vbr on CdV/dt Protection Diode