ZHCSD75D March 2014 – January 2018
For highest voltage measurement accuracy, it is critical to connect the BAT pin directly to the battery terminal PCB pad. This avoids measurement errors caused by IR drops when high charge or discharge currents are flowing. Connecting right at the positive battery terminal with a Kelvin connection ensures the elimination of parasitic resistance between the point of measurement and the actual battery terminal. Likewise the low current ground return for the fuel gauge and all related passive components should be star-connected right at the negative battery terminal. This technique minimizes measurement error due to current-induced ground offsets and also improves noise performance through prevention of ground bounce that could occur with high current and low current returns intersecting ahead of the battery ground. The bypass capacitor for this sense line needs to be placed as close as possible to the BAT input pin.