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BQ29209-Q1: Absolute maximum ratings

Part Number: BQ29209-Q1
Other Parts Discussed in Thread: BQ29209

Hello team,

I am Oliver, FAE in Korea automotive market.

Can I get BQ29209-Q1 absolute maximum ratings for these?

1. Supply current range

2. Input current range

Thank you.


Oliver Kim

  • Hi Oliver,
    1. Supply current is limited by the applied voltage and internal resistances. Its current distribution is shown in the electrical characteristics table as ICC, however the cell balance current and output current can also flow through the VDD pin. The designer should also consider those currents.
    2. Input current for the cell inputs is shown in the electrical characteristics as IIN, and ICB_EN for the Cell balance enable. The VC1_CB pin does not have a stated abs max input current, current is set by the external voltage and resistance and is recommended as 15 mA maximum in section 7.6 and 8.1.2.
  • Hello WM5295,

    Thanks for your reply.

    1. I get the point that I should consider other factors, but that's why I need supply current maximum rating. What does it mean when I consider current, but doesn't know how much the device can manage..?

    2. Based on 8.1.2 "If the internal cell balancing current of up to 15 mA is insufficient, the bq29209-Q1 may be configured via external
    circuitry to support much higher external cell balancing current", it seems that BQ29209-Q1 is capable of more than 15mA if external circuit is used. It sounds BQ29209-Q1 can have enough margin over 15mA, but no more guidance for that in datasheet.

    As you know BMS(Battery management system) is very critical application in perspective of safety. To satisfy higher ASIL rank requirement, absolute current rating is important in system level. Is there any chances that current absolute value can be provided from BU side? If you think it's not available or technically meaning-less in IC level, could you please explain the details? It would be helpful to make my customers be cleared about that.

    Thank you.

    Oliver Kim
  • Hi Oliver,
    1. In addition to the specifications noted above, there is the IOH_ZV High-level short-circuit output current of 8 mA which will come from the supply. This will bound the load current portion of the total supply current.
    2. No absolute max supply current is presently or available. As a worst case you may need to consider system current if the part is shorted in which case the current would be limited by other components. Regarding the balance current 7.3 includes Cell balance resistance RCBext with a minimum of 100 ohm, section 7.6 with a 15 mA as well as in text. The part will have some margin above 15mA but it is not specified, to achieve more than 15 mA balance current the circuit in 9.3.1 is offered. In the figure 12 circuit the higher balance current does not flow in the BQ29209 but in the external circuit, the current in the part will be limited by the RCLAMP resistor. I do see a point in that if the circuit is designed for a 15 mA balance current at 3.8 or 4V, but the board is tested with the sources for VC1 = VC2 = VDD = 10V (within abs max) with cell balancing enabled the cell balance current would be significantly higher and there is no guidance if this is OK. But the limits currently known are listed.