BQ79656-Q1: Issue with BQ79656 Custom PCB and Auto Address Function

Ajanish V

Part Number: BQ79656-Q1
Other Parts Discussed in Thread: USB2ANY

Tool/software:

Hi,

I have developed a PCB with the BQ79656 IC, and the isolation board is a separate PCB with capacitor isolation, as described in the BQ79656 datasheet under "Capacitor Isolation on Different PCB." We tested the setup using USB2ANY via the 10-pin connector connected to the BQ79600 EVM, using the cable provided with USB2ANY. The BQ79600 COMH is connected to the custom board’s COML.

Out of the five boards assembled, only two are working. All five boards receive the wake-up signal, and the LED connected to AVDD turns on when the wake-up command is issued through the GUI. However, the Auto Address function does not produce any results on three boards.

I seem to be encountering the same issues mentioned in this post: "BQ79656-Q1: Unable to communicate using BQ79600EVM - Power management forum - Power management - TI E2E support forums"

Could you please advise us on how to resolve this?

Regards,
Arun

8 months ago

0 Abdelrahman Aldmour 8 months ago

TI__Intellectual 1520 points

Hey Arun,

This issue is generally due to an incorrect isolation schematic, poor connection between isolation components, or the BQ79656's power supply is clamping the input current (a current clamp around 50mA or more is fine). Can you provide you isolation schematics to be reviewed?

Regards,

Abdel

0 Ajanish V 7 months ago in reply to Abdelrahman Aldmour

Prodigy 10 points

Hey Abdel,

Sorry for the late reply. I debugged the problem, and the issue was with the isolation circuit on the two non-working boards. The isolator was mounted, and we were trying to communicate using the COMH and COML ports. Once we removed the isolator (ISO7742FDBQR), both boards started communicating.

I have attached the isolator schematics:

Even when the isolator is not mounted should we populate the pull-up resistor for RX_BQ?

Regards,
Arun