Other Parts Discussed in Thread: BQ76942
Tool/software:
Hi,
We are using the BQ7791501 in a 10-series configuration.
For some reason, we are operating a transistor along with the discharging MOSFETs, that has increased the current in the lower 5 cells to 150µA, while the upper 5 cells have a current of only 20µA. To balance this, what changes should we make?
- Can we decrease Rctrd to 220kΩ or lower?
- Should we use external resistors between the upper device DSG and VSS pins? What is the minimum value we can use?
- We are using the CTRD switch directly (without any resistance) at the VDD and CTRD pins of the lower device. Is this correct?
- How can we balance the CTRD and DSG pin currents of the upper and lower devices when the switch is OFF?
- When the switch is OFF, the lower device current is minimal (transistor + DSG MOSFETs are OFF), but the external resistor connected between the upper device's DSG and VSS pins remains active, causing an imbalance between the upper 5 and lower 5 cells.
- How can we ensure balance even when the switch is OFF?
- Should we use a switch at the upper device instead of the lower device? or Should we use a switch at the upper device DSG pin output?
Please suggest a solution.
Edited:
I have tried using a switch between CTRD and VSS of the upper device with a 1.5MΩ pull-up to VDD. Turning on the switch enables the DSG output, and the switch function works smoothly most of the time. However, occasionally, a locking condition occurs, causing the DSG output to remain permanently ON regardless of the switch state.
I have used R_CTRD and R_CTRC = 1MΩ.
Please check and suggest a solution as soon as possible.
