I'm trying to understand the sample rate of the coulomb counter in the bq20Z75-V180. Our load has current pulses at about 30 kHz, and we want to make sure that the chip doesn't miss the pulses and thus under-count the current. From the datasheet:
Charge and Discharge Counting
The integrating delta-sigma ADC measures the charge/discharge flow of the battery by measuring the voltage drop across a small-value sense resistor between the SRP and SRN pins. The integrating ADC measures bipolar signals from –0.25 V to 0.25 V. The bq20z75-V180 detects charge activity when VSR = V(SRP)–V(SRN) is positive and discharge activity when VSR = V(SRP)–V(SRN) is negative. The bq20z75-V180 continuously integrates the signal over time, using an internal counter. The fundamental rate of the counter is 0.65 nVh.
I'm a little unclear what this is telling me. The datasheet doesn't give the clock rate of the delta-sigma ADC. It does use the words "continuously integrates," but then it says it uses a counter, which is by nature not a continuous device. The fundamental rate is expressed as 0.65 nVh, which isn't really a rate but rather expresses the smallest counter increment.
So, the question remains, unless I'm missing something: is there a load current frequency above which the chip will fail to accurately accumulate the coulomb count? Or is there some sort of analog integration happening which removes this as a potential problem?
Thanks, Scott
