Datasheet
DS2746 Low-Cost 2-Wire Battery Monitor
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Table 3. Accumulated Current Range for Various RSNS Values
ACR RANGE
R
SNS
V
SS
- V
SNS
20m 15m 10m 5m
409.6mVh 20.48Ah 27.31Ah 40.96Ah 81.92Ah
CURRENT OFFSET BIAS
The Current Offset Bias register (COBR) allows a programmable offset value to be added to raw current
measurements. The result of the raw current measurement plus the COBR value is displayed as the current
measurement result in the CURRENT register, and is used for current accumulation. The COBR value can be used
to correct for a static offset error, or can be used to intentionally skew the current results and therefore the current
accumulation.
Read and write access is allowed to COBR. Whenever the COBR is written, the new value is applied to all
subsequent current measurements. COBR can be programmed in 1.56V steps to any value between +198V and
-200V. The COBR value is stored as a two’s complement value in volatile memory, and must be initialized via the
interface on power-up. Figure 10 describes the COBR address, format, and resolution.
Figure 10. Current Offset Bias Register Format
Address 61h
S 2
6
2
5
2
4
2
3
2
2
2
1
2
0
MSb LSb
“S”: sign bit
Units: 1.56V/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 + COBR) falls in one of two defined
ranges. The first range prevents charge currents less than 100V/R
SNS
from being accumulated. The second range
prevents discharge currents less than 25V/R
SNS
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
Status/Config register. See the register description for additional information.
ACCUMULATION BIAS
The Accumulation Bias register (ABR) allows a programmable offset value to be added to the current accumulation
process. The new ACR value results from the addition of the Current register value plus ABR plus the previous
ACR value. ABR can be used to intentionally skew the current accumulation to estimate system stand-by currents
that are too small to measure. ABR value is not subject to the Current Blanking thresholds.
Read and write access is allowed to the ABR. Whenever the ABR is written, the new value is applied to all
subsequent current measurements. ABR can be set to any value between +193.75V and -200V in 6.25V steps.
The ABR value is stored as a two’s complement value in volatile memory, and must be initialized via the interface
on power-up. The lower two bits of the ABR register have no effect on the data. Figure 11 describes the ABR
address, format, and resolution.