Other Parts Discussed in Thread: BQ76940, , BQ34Z100-G1
I am designing a BMS for a 12s stack, very similar to TIDA-010030 reference design, but when it came to the sense resistor selection, I ran into some trouble. So naturally, I have a few questions about the sense resistor selection as outlined in the BQ76940 datasheet. In the datasheet on page 46, it outlines the exact current I'm planning to sense, but I think there's a mistake. I chose cells that had a max continuous current of 10A. So the example in the datasheet work for me, BUT - something is wrong with the math presented. RSNS has a maximum range of +/-200mV with an absolute max of 300mV. If we're considering an Iscd of 25A over the absolute maximum range, that calls for a 12.5mR sense resistor, not 7.5mR as the datasheet says. I've been trying to figure out where that number comes from and can't seem to get it close. Can you elaborate? Also, in your TIDA-010030 reference design, they're using 1mR as a sense resistance, and that tells me that you're expecting an 18650 cell to output a maximum of 200A - something doesn't' seem right - can you elaborate on this?