Other Parts Discussed in Thread: BQ78350-R1A, , BQSTUDIO, TIDA-00449
Tool/software:
Hi Team,
We have developed a low-side 6S to 10S BMS using the BQ76930 and BQ78350-R1A.
During testing in a 6S configuration, we encountered a few issues, outlined below:
1) Initial Test Behavior:
In the first test, the board functioned correctly—discharge was allowed, and both DSG and CHG pins were active as seen in BQStudio. The DSG pin was outputting ~7.9V–8V (with respect to GND).
2) Issue During OCD/OCC Testing:
While performing functional tests for Overcurrent in Discharge (OCD) and Overcurrent in Charge (OCC), we observed that once an OCD condition was triggered (intentionally, at a very low current), discharge was no longer allowed—even though the XDSG bit was not set and the DSG bit was set in the Operation Status. Measuring the voltage between the DSG pin (FET gate) and GND showed only ~0.4V.
This issue has been observed consistently across all 10 boards: discharge is permitted initially, but after triggering OCD once, the DSG pin voltage drops and the board no longer allows discharge.
3) Hardware Changes & Observations:
We attempted a hardware modification—desoldering the gate resistors and shorting them directly, while also removing R124. After this, we measured ~8V on the DSG pin. However, replacing the resistors with new ones caused the issue to reappear, with the DSG pin voltage dropping back to ~0.4V.
I can share the Schematic and PCB file on pvt chat for review. Please do help us in troubleshooting.
Note: Reference used: https://www.ti.com/lit/ug/tiduar8c/tiduar8c.pdf (TIDA-00449)
Thanks and Regards
Noel Binny Abraham
