BQ78350-R1: SMBUS Communication failed with BQ-studio.

Hello Dhaval,

Are you using a custom board or our Evaluation Board (EVM)? 

In our EVM, the SMBus communication 3.3V comes from the EV2400 attached at J17. Figure 39 from the  bq76930 and bq76940 Evaluation Module

The REGOUT from the BQ76930 monitor device is used to power VCC in the BQ78350. And, REGOUT is also used to power the I2C communications lines in the BQ76930.

Please compare the communication connections directly with the BQ76930 EVM.

Regards,
Jose Couso

Hello Jose Couso,

I agreed with your suggestion. I have two custom battery pack board which used to communicate with BQ studio.

both custom board include BQ7693006DBTR, BQ78350-R1 and BQ769200PWR ICs. one of the board has successfully communicated with BQ studio  and proper working.

second one is failed.

I have checked all criteria, components, design circuit etc. all match with EVM. but  how did resolve this problem. please suggest best solution..!

also we observe that board all LED indication and its charging status as percentage wise LED ON. We re-solder or replace  parts at SMBUS like 100 ohm,1 M Ohm resistor and protection diode.

Hello Dhaval,

Are the two custom boards the same? If so, they should both work identical. Maybe compare both of your custom boards and see what is different.

Are you connecting both boards at the same time with BQStudio? Also, just to clarify, it is only the BQ78350 who will talk to BQStudio over SMBus. The BQ76930 will communicate directly with BQ78350 over I2C. 

The SMBus communication lines should show 3.3V if connected to the EV2400. 

Regards,
Jose Couso

Dear Jose

Yes, both two custom boards are same and work. we connected boards one by one individual  with BQ studio at different time slot. one of the board proper communicate with Bq studio and working successfully  then after it disconnected and take second board to communicate.

We sure about that only BQ78350 will communicated over SMBus and AFE- BQ76930 will directly interface over  I2C with fuel gauge IC.

Absolutely you are right  about  that ,we observe SMBus communication lines shown 3.3V when connected to EV2400.

Hello Dhaval,

dhaval prajapati said:

Absolutely you are right  about  that ,we observe SMBus communication lines shown 3.3V when connected to EV2400.

Is the issue fixed now? Initially your concern was the SMBus communication lines were at 0V, but now it seems you understand why. 

Please let me know if there's anything else I can help with.

Regards,
Jose Couso

Hello Jose,

I understand the SMBus voltage concept but facing issue in second board. when  2nd custom board connected to EV2400 still not observed 3.3V at SMBus.

we again double checked all components related SMBus there is no issue found and proper soldered at board.

is there any solution on SMBus?

Hello Dhaval,

If both custom boards are identical, what is failing? One of them has 3.3V when EV2400 is connected, the other one does not. Have you probed nearby the EV2400 port on both boards? Please do so and see where it fails. 

Regards,
Jose Couso

Hello Jose,

I have probed nearby the EV2400 port on both boards, we measure 3.3V when connected to custom BMS board.

but same problem facing,

Hi Dhaval,

Something is not adding up here.

You mentioned: 

dhaval prajapati said:

when  2nd custom board connected to EV2400 still not observed 3.3V at SMBus.

Latest reply:

dhaval prajapati said:

I have probed nearby the EV2400 port on both boards, we measure 3.3V when connected to custom BMS board.

I am a bit confused. Where are you probing at? Please share schematic and setup if possible, and kindly point out where you are probing.

Regards,
Jose Couso

Hello Jose,

I have shred a Schematic PDF file and setup JPG file for your references.

I have probed at TP 15 & TP16 to measure 3.3V when connected to EV2400. also probed at EV2400 SMBus cable connector.

Another  issue found at ALERT pin (TP 8) remains High -2.5V observed at TP 8. I prefer a BQ78350 and BQ76930 related documents and reference technical manual. 

In BQ78350 Technical references shows 3.6.3 AFE ALERT OVRD Protection section says the device can detect an external override signal.so that ALERT pin remains HIGH, please suggest solution to overcome this issue.24V_6S_BMS.pdf24V_6S_BMS_3D_PCB.pdf

Hello Dhaval,

Sorry for the late response, E2E website was down for maintenance.

The ALERT pin high is a common condition in the BQ76930. This is a very noise sensitive pin and it can stay high if too much capacitance is seeing, a time constant filter of 250us is recommended at the pin. Please check the following threads for better debugging  and more details.

Thread-1
Thread-2
Thread-3
Thread-4

Regards,
Jose Couso

Hello Jose,

Thank you for sharing a threads. I hope it might be great helpful to resolve my problem.

I have another question about my schematic ,please review and suggest if any changes required in hardware design schematic.

we will solve alert pin issue when my custom board communicate with BQ studio.

still we working on SMBus failure analysis and try to solve.

Hello Dhaval, 

dhaval prajapati said:

I have another question about my schematic ,please review and suggest if any changes required in hardware design schematic.

Is there a specific area where you would like the schematic to be reviewed? The best approach is to compare it directly with the EVM schematic. 

Also, we do have a Reference Design that showcases the BQ78350 + BQ76940 + BQ76200. TIDA-00792

Regards,
Jose Couso

Thank you Jose,

I will refer TIDA-00792 reference design and compare my custom board design schematic. if any specific requirement does not match with custom board or resolve my query, will update soon...!

Hi Dhaval,

Sounds great. 

Regards,
Jose Couso

Hello Jose,

I have facing another issue when custom board connected to EVM and PC. SMBUS communicate few second after that automatically shutdown BQ-Studio.

and error shows battery status indicate 771%. I have attached a snapshot.

Hello Dhaval,

What is the custom board? What is the circuit design and why are you connecting it to the EVM?

BQStudio is not detecting the right FW. It is not reading correctly. Please elaborate your use case so I can further guide you.

Regards,
Jose Couso

I have a custom BMS board which included BQ78350,BQ76930 AND BQ76200 ICs. I am talking about the board that is being discussed in past threads.

Earlier there was a talk about two BMS board ,one of board facing SMBus communication failed and shutdown BQ studio.

Hi Dhaval,

Why are you interfacing your custom board with the TI's EVM? This can create communication problems as BQstudio won't know which device to talk to.

Please elaborate on your set up and what is it you are seeing. 

Regards,
Jose Couso