BQ76940EVM: BQ78350-R1 Fuel Gauge with BQ76940

Yusuf KAYA

Part Number: BQ76940EVM
Other Parts Discussed in Thread: BQ76940, BQ78350-R1

Hi,

I have designed a BMS by using BQ78350-R1 and BQ76940 for 14-Series Li-Ion Cell Pack. My design is almost the same as "Multicell 36-V to 48-V Battery Management System Reference Design". When i plug in the 14-series cell pack to BMS, the bq76940 IC fails and sometimes BQ78350-R1 as well.

Do you have a suggestion to solve this problem or is there anybody who has the same experience?

over 6 years ago

0 Matt Sunna over 6 years ago

TI__Guru* 81034 points

Hi Yusuf,

When you say the IC fails, can you explain more? The best starting place for debug is to start checking the expected voltages at different pins for the BQ76940 - check REGIN, REGOUT, BAT, VC5X, VC10X, and the VC pin voltages. Check communication with the I2C port.

Matt

0 Matt Sunna over 6 years ago in reply to Matt Sunna

TI__Guru* 81034 points

Hi Yusuf,

Do you have any additional information you can share or has the issue been resolved? I will go ahead and close this thread. If you respond it will automatically reopen.

Thanks,
Matt

0 Yusuf KAYA over 6 years ago in reply to Matt Sunna

Intellectual 630 points

Hi,

I am still trying to find the existing problem and measuring some voltages. I think I will be come back with some findings. However, I have a question about the "NT4, Net-Tie" between Regout and Vcc in "Multicell 36-V to 48-V Battery Management System Reference Design". It says "No solder mask opening, no solder paste" Can you tell me what it is for? and Is it a pad or trace? Please see attached file to find the NT4 marking image. Besides, There is not a resistor between Source and Drain of the Q21 such as 10M in Reference Design. Can it be a problem?

Thanks in advance.

0 Matt Sunna over 6 years ago in reply to Yusuf KAYA

TI__Guru* 81034 points

Hi Yusuf,

A net tie is a connection between 2 nets. It comes from Altium and there are a couple of good links here to learn about these:
smtnet.com/.../NetTies-and-How-to-Use-Them.pdf
www.altium.com/.../((Creating Connectivity))_AD

I am not sure what you are referring to with Q21. Q21 is not populated on the TI reference design.

Matt

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BQ76940EVM: BQ78350-R1 Fuel Gauge with BQ76940