Rainbow Electronics DS2781 - Manual (Page 11)

DS2781: Two-Cell Standalone Fuel Gauge IC
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ACCUMULATION BIAS
The Accumulation Bias register (AB) allows an arbitrary bias to be introduced into the current-accumulation
process. The AB can be used to account for currents that do not flow through the sense resistor, estimate currents
too small to measure, estimate battery self-discharge or correct for static offset of the individual DS2781 device.
The AB register allows a user programmed constant positive or negative polarity bias to be included in the current
accumulation process. The user-programmed two’s compliment value, with bit weighting the same as the current
register, is added to the ACR once per current conversion cycle. The AB value is loaded on power-up from
EEPROM memory. The format of the AB register is shown in Figure 10.
Figure 10. Accumulation Bias Register Formats
AB EE
Address 61h
S 2 6 2 5 2 4 2 3 2 2 2 1 2 0
MSb LSb
“S”: sign bit Units: 1.5625 mV/Rsns
CURRENT BLANKING
The Current Blanking feature modifies current measurement result prior to being accumulated in the ACR. Current
Blanking occurs conditionally when a current measurement (raw current + COB) falls in one of two defined ranges.
The first range prevents charge currents less than 100µV from being accumulated. The second range prevents
discharge currents less than 25µV in magnitude from being accumulated. Charge current blanking is always
performed, however, discharge current blanking must be enabled by setting the NBEN bit in the Control register.
See the register description for additional information.
CAPACITY ESTIMATION ALGORITHM
Remaining capacity estimation uses real-time measured values and stored parameters describing the cell stack
characteristics and application operating limits. The following diagram describes the algorithm inputs and outputs.