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BQ76952: Random Cell Connection Support

Toad F
Prodigy 30 points
Part Number: BQ76952

Tool/software:

Hi, the BQ76952 function supports Random Cell Connection. I would like to ask the following questions and help answer them. Thank you.
1. If it cannot be guaranteed that the VC0 of BQ76952 will be powered on first, what problems will arise for the chip?
2. Is it possible to connect VC0 to VSS through a resistor or Schottky diode on the PCB without worrying about whether VC0 is powered on immediately? Can VC0~VC16 be powered on randomly?
3. About Random Cell Connection, is there any relevant documentation to provide reference?
4. TI's future AFE will plan to power on in disorder, does it not necessarily have to guarantee the rule of VC0 powering on first?

  • 0
    TI__Expert 8480 points

    Hello Toad,

    Toad F said:
    About Random Cell Connection, is there any relevant documentation to provide reference?

    Our part supports random cell connection with some restrictions. This Connecting Battery Cells to the BQ769x2 Family FAQ should be a useful guide.

    Toad F said:
    If it cannot be guaranteed that the VC0 of BQ76952 will be powered on first, what problems will arise for the chip?

    We have seen in some unique cases of when users use a relay module to do cell connections in a certain way, when VC0 is not connected first before any connection, it has caused some issues (BQ76952: BQ76952 (Cell Connection Sequence)). Other than that, I don't think there have been any more to my knowledge. 

    Toad F said:
    Is it possible to connect VC0 to VSS through a resistor or Schottky diode on the PCB without worrying about whether VC0 is powered on immediately? Can VC0~VC16 be powered on randomly?

    We do not recommend having resistances between VC0 and BAT-/Vss as it can cause measurement errors in Cell 1 (Cell 1 Voltage Measurement when VC0 is above VSS).

    It should be fine to use a Schottky diode or Zener diode in between VC0 to VSS. We have a reference design, TIDA-010208, that shows this. This previous post also briefly discusses this: Correct VC Connections for 3S and Upwards.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 30 points
    Hi Alexis， Thank you for your response.
    If it use a Schottky diode or Zener diode in between VC0 to VSS(GND). As shown in the following picture. Can VC0~VC16 be powered on randomly? No longer need to ensure that VC0 is connected to the battery cell first？
  • 0 in reply to Toad F
    TI__Expert 8480 points

    Hello Toad,

    I think those Zener diodes should help. From previous users, it seems that VC0 would go outside the recommended range. The Zener and Schottky diodes should help prevent that.

    Best Regards,
    Alexis