BQ40Z80: SMbus communication and Schematic check

Robin Yu

Part Number: BQ40Z80

Hi team,

Customer is using BQ40Z80 for 6S battery design.

They find the communication between their own MCU and BQ40Z80 is not good, the ACK is received from slave after about 25ms.

And the ACK is received from slave after about several hundred of us for TI EVM.

The result is as below.

(1) Their MCU+their BQ40Z80 board.-->Not good.

(2) Their MCU+TI BQ40Z80 EVM board.-->Good.

(3) TI EVM MCU+their BQ40Z80 board.-->Not good.

(4) TI EVM MCU+TI BQ40Z80 EVM board.-->Good.

So it seems this is caused by their Schematic design. Could you please help review it?

Only photo could be provided due to customer policy. Sorry about this.

Thanks.

Robin

0 Batt over 6 years ago

Hi Robin,

The image is not clear. Please ask them to follow the reference schematic with unused pins disabled as specified in the DS. That's all I can suggest.

0 Robin Yu over 6 years ago in reply to Batt

Hi Batt,

You mean this is caused probably by multi-functional pin configuration? Thanks.

Robin

0 Robin Yu over 6 years ago in reply to Robin Yu

Hi Batt,

Updated as below.

SMBus is connect to both BQ40Z80 and EEPROM(I2C). The data rate is 50kbps. The issue is as previous description.

1. Customer takes the EEPROM off, the communication becomes normal;

2. Customer changes the data rate to 60~100kbps, while the EEPROM is on the board, the communication becomes normal.

Do you have any suggestion to figure out the root cause?

Thanks.

Robin

0 Batt over 6 years ago in reply to Robin Yu

Hi Robin,

It is possible that the gauge is detecting false comms to it's address. You may want to use a buffer to isolate the gauge.

0 Robin Yu over 6 years ago in reply to Batt

Hi Batt,

The customer has solved the issue by AB-BA test. It seems the BQ40Z80 on customer board is failed.

Thanks.

Robin

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