SDAA369 August   2026 BQ76952 , BQ78706

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2CELL Open-Wire Detection Flow
    1. 2.1 VC1-VCn-1 Open-Wire Detection
    2. 2.2 VCn Open-Wire Detection
    3. 2.3 VC0 Open-Wire Detection
  6. 3Shunt Open-Wire Detection
    1. 3.1 Open-Wire Detection Solution of Shunt
    2. 3.2 Current-Sense Diagnostics with Redundant ADC
  7. 4Other Diagnostics: VBAT, VSS
    1. 4.1 VBAT Open-Wire Detection
    2. 4.2 VSS Open-Wire Detection
  8. 5Summary
  9. 6References

3.1 Open-Wire Detection Solution of Shunt

Open-Wire Detection Solution of Shunt Figure 3-1 Open-Wire Detection Solution of Shunt

As shown in Figure 3-1, this article proposes a low-cost diagnostic circuit by adding a resistor divider between the series filter resistors and the MCU GPIO pins. During normal operation, the MCU pins remain in a high-impedance state (Hi-Z), so the circuit does not introduce additional static power consumption.

During the diagnostic operation, the MCU drives the GPIO pins high. This pulls the SRN/SRP pins to a level that is high enough to generate a clearly measurable signal for the internal ADC of the AFE. By reading the AFE current measurement, the MCU can determine whether the SRP and SRN pins are shorted together or shorted to VSS. If the filter resistors and the current-sense wires are not open, the current value reported by the AFE should match the expected value calculated from the resistor-divider network. If a filter resistor or current-sense wire becomes open, the voltage applied to the current-sense input is determined mainly by the MCU pull-up voltage, which can directly trigger SCD protection.

Note: When designing this circuit, make sure that the voltage applied to the AFE current-sense input pins, SRP and SRN, does not exceed the absolute maximum ratings of these pins. Otherwise, the MCU pullup voltage may damage the AFE.