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smiller9
smiller9
Visitor II
December 14, 2016
Question

VND5T100 - Reverse polarity protection

  • December 14, 2016
  • 2 replies
  • 1748 views
Posted on December 14, 2016 at 07:23

Hello,

I have made the reverse battery protection according to the datasheet and the UM1557 (user manual) with a diode in the GND line in parallel to a 4.7kOhm resistor.

But if I do a reverse supply I detected a high current consumption.

This is due to the resistors at the CS outputs that are connected to ground. In my case these are 2.2kOhm resistors. They are only of the size 0603 and they will get destoryed in case of battery reversal.

But there is no advice in the datasheet or the user manual. What can I do to protect these resistors. Is it only possible by increasing the case size?

This topic has been closed for replies.

2 replies

F G
F G
Visitor II
February 8, 2017
Posted on February 08, 2017 at 10:06

Hi, where do you detect the high current? Are you referring to the output current (Iout) or to the CS current? Which load are you using? Value of reverse battery?

Mauro Chiara
Mauro Chiara
Visitor II
May 29, 2017
Posted on May 29, 2017 at 11:29

Hi,

I had a similar issue with VND7140AJ.

I have mounted the inversion protection circuit suggested in the datasheet (using a shottkly diode).

When I gave 12Vdc reverse supply voltage I have the ic irremediably damaged.

As a matter of fact, I had 20ohms between the Vcc and the GND pin of the 

VND7140AJ.

What could be the cause of such a break down?

Thank you

Best Regards,

Mauro Chiara

Nickname15513_O
Nickname15513_O
ST Employee
June 13, 2017
Posted on June 13, 2017 at 10:53

Hi,

could you please provide further info about the components used for the protection circuit?

Have you already had a look at the Application Note UM1922?

Best regards.

Davide

Mauro Chiara
Mauro Chiara
Visitor II
June 15, 2017
Posted on June 15, 2017 at 10:00

Hi,

Thank you for your reply.

Please see the attached schematic.

I'm using a schottky SS14. R18 is not mounted because my load is purely resistive.0690X00000607HTQAY.png

In the next release I will pull FaultRST and SELn to GND through a 10k resistor. Then I will add a filtering capacitor on the V_power.

At the moment I have solved the problem inserting a diode against inversion also in the positive supply side.

Before that I had many 

VND7140AJ damaged.

Best Regards

Mauro Chiara

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