BQ79616-Q1: Internal protection diode for VBAT & VC channel

Jass Jin

Part Number: BQ79616-Q1
Other Parts Discussed in Thread: BQ79616

Hi expert,

My customer found that if the cable of VBAT is broken, the current can go through the internel dioder of VC16 and power VBAT, the BQ79616 can work normally.

In this case will the working current damage this diode? What's the maximum conducting current of this diode?

Thanks!

over 1 year ago

0 Jass Jin over 1 year ago

TI__Intellectual 2475 points

Any feedback, Thanks!

0 Jass Jin over 1 year ago

TI__Intellectual 2475 points

Any feedback?

0 Anthony P Pham over 1 year ago in reply to Jass Jin

TI__Mastermind 23410 points

Hi Jass,

Apologies for the late response.

The VC16 pin is only intended as a sense pin and any additional current that is pulled will affect the ADC readings. This is not an intended functionality of the VC16 pin and we do not recommend it.

As shown in the image you have, the top battery cell still has a connection to the BAT pin. Is this connection completely broken if the cable is broken or is this an onboard trace that is still valid?

From what I can see on EVM, if I remove the 30 Ohm resistor, I am not able to power the device.

I will investigate the internal diode current if and update.

Best Regards,

Anthony Pham

0 Jass Jin over 1 year ago in reply to Anthony P Pham

TI__Intellectual 2475 points

Hi Antohny,

Thanks for you reply!

0 Jass Jin over 1 year ago in reply to Jass Jin

TI__Intellectual 2475 points

Hi Antohny,

Can you remove the cable of VC15 after normal power-up to see whether 616 can keep working?

0 Jass Jin over 1 year ago in reply to Jass Jin

TI__Intellectual 2475 points

Hi Antohny,

Customer's test case only use 10 channels, battery top only connects to VC10 but not VPWR(Vbat & NPN).

During their test, the 616 can be woke up and send frame to daisy chain. The D6 is removed in the test.

Can you reproduce this case?

By the way, customer wants to know the internal diode current maximum value.

Thanks!

0 Anthony P Pham over 1 year ago in reply to Jass Jin

TI__Mastermind 23410 points

Hey Jass,

Understood. Looks like on my end this was a setup issue. It does look like you can power the device through VC16 as the customer has seen.

As I mentioned before this is incredibly not recommended. I'd like to be clear that the customer should not use this as a permanent solution. We highly advise to repairing the harness as this is not an intended use of the VC16 pins.

The diode I've been told can handle up to about 10 mA.

Again, I'd like to be clear that this is not advised as a permanent solution. Doing this can degrade the ESD diode as well as affect voltage measurements for VC16.

Best Regards,

Anthony Pham

0 Jass Jin over 1 year ago in reply to Anthony P Pham

TI__Intellectual 2475 points

Thanks Antohny, customer doing this is just verify what will happen when cable is broken.

0 Anthony P Pham over 1 year ago in reply to Jass Jin

TI__Mastermind 23410 points

Hey Jass,

When the cable is broken, the device may have current powering it through the internal diode but again this is not recommended. This can cause inaccuracies in VC readings due to the IR drop and decrease reliability of the ESD diode that's used on the VC pins as this is outside of the normal operating conditions.

Again, we strongly advise against this.

Best Regards,

Anthony Pham

0 Jass Jin over 1 year ago in reply to Anthony P Pham

TI__Intellectual 2475 points

In this case, we just want to know the working current damage this diode.

We don't want it happens, but at some time, there might be some case this cable is broken.

0 Anthony P Pham over 1 year ago in reply to Jass Jin

TI__Mastermind 23410 points

Hi Jass,

I understand. The working current I was told was about 2 mA. Again I emphasize this should be repaired and is not the intended case of the VC pins.

Best Regards,

Anthony Pham

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BQ79616-Q1: Internal protection diode for VBAT & VC channel