BQ76972: Clarification on CC Gain Formula and Coulomb Counting Methods

Tool/software:

1. Clarification on CC Gain Formula

We are using a shunt resistor value of 0.25 mΩ and need clarification on the appropriate CC Gain value to be programmed in the calibration register for current scaling.

Datasheet vs Application Note Variance:

We have come across two different formulas for calculating CC Gain depending on use case:

1. For Internal Coulomb Counting (AFE PassQ):

CC Gain = 7.4768 / Rsense(mΩ)

Example (0.25 mΩ):

CC Gain = 7.4768 / 0.25 = 29.9072 (rounded as needed)

1. For External Integration (MCU-based):

CC Gain = 20,000 / (Rsense(Ω) × 32767)

Example (0.00025 Ω):

CC Gain = 20,000 / (0.00025 × 32767) ≈ 2442.7 μV/LSB

Question:

• Can you confirm that these two formulas are both valid but intended for different integration strategies (internal vs external)?
  
  

Should we use the 7.4768-based formula only if relying on PassQ / internal integration, and the 2443 μV/LSB value only if reading current externally via CC2?

2. Clarification on Coulomb Counting Comparison: Internal vs External

We are evaluating whether to use the internal charge integration feature (PassQ) or perform external coulomb counting in the MCU using CC2 data.

Summary of Current Understanding:

Questions:

• Is our comparison accurate in terms of performance and use-case suitability?
  
  
• Are there other hidden advantages or limitations in PassQ that we should be aware of?
  
  

For a system requiring high-speed SoC tracking (fast load changes), is external integration definitively recommended?