TPS25944A: Reverse Polarity Protection - output diode

Arnaud Puret

Part Number: TPS25944A

Hi,

On the Reverse Polarity Protection (figure 86 from the datasheet, see below), a diode connected to the output and the return path is needed.

Is this diode a part of the Reverse Polarity Protection?
Is it a protection against inductive effect of the load (related to the Schottky diode from the figure 87)?
can you give me some requested characteristics of this diode?

Thanks for your help.

Best regards,

Arnaud Puret.

over 4 years ago

0 Kunal Goel over 4 years ago

TI__Guru* 79001 points

Hi Arnaud,

Thanks for reaching out! I will get back to you by tomorrow!

Regards

Kunal Goel

0 Kunal Goel over 4 years ago in reply to Kunal Goel

TI__Guru* 79001 points

Hi Arnaud,

It is the schottky diode for protection from transients due to line inductance.

Regards

Kunal Goel

0 Arnaud Puret over 4 years ago in reply to Kunal Goel

Prodigy 80 points

Hi Kunal,

Thanks for your answer.

Is this diode enough to protect the eFuse against the reverse voltage of an inductive load (electromechanical lock connected between Out and GND)? It seems to me that the reverse polarity protection diode prevent this usage... In this case, do I need one more diode between Out and GND?

Best regards,

Arnaud Puret

+1 Kunal Goel over 4 years ago in reply to Arnaud Puret

TI__Guru* 79001 points

Hi Arnaud,

In the case of a short circuit and overload current limit when the device interrupts current flow, the input inductance generates a positive voltage spike on the input, and the output inductance generates a negative voltage spike on the output. To protect from this negative spike schottky is used. You have to select schottky such as its forward voltage drop is near to minimum voltage on input pin and its non repetitive peak surge current is atleast 1.5*fastrip current.

Regards

Kunal Goel

0 Arnaud Puret over 4 years ago in reply to Kunal Goel

Prodigy 80 points

Hi Kunal,

Thanks for the details of the Schottky diode role and some hints to select the right one.

What leaves me perplexed is the connection of this diode to the return path (the "reverse polarity protected GND"), not the board GND (figure 86).

Can the Schottky diode be connected to the board GND, if the negative voltage spike comes from the output inductance?

Best regards,

Arnaud Puret

0 Kunal Goel over 4 years ago in reply to Arnaud Puret

TI__Guru* 79001 points

Hi Arnaud,

I will get back to you by tomorrow.

Regards

Kunal Goel

+1 Kunal Goel over 4 years ago in reply to Kunal Goel

TI__Guru* 79001 points

Hi Arnaud,

I think there is some mistake in diagram. The schottky should be connected to board GND. You are right that as per connection in datasheet the reverse polarity protection diode is blocking the schottky usage.

Regards

Kunal Goel

0 Arnaud Puret over 4 years ago in reply to Kunal Goel

Prodigy 80 points

Hi Kunal,

Thanks for your confirmation, all make sense now !

Best regards,

Arnaud Puret

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TPS25944A: Reverse Polarity Protection - output diode