DS2756: High-Accuracy Battery Fuel Gauge with Programmable Suspend Mode

command targeting the ACR register address. A write to the ACR results in an automatic copy of the new value to

EEPROM.

Figure 5. Accumulated Current Register Format

MSB-Address 10h

LSB-Address 11h

S

2

14

2

13

2

12

2

11

2

10

2

9

2

8

2

7

2

6

2

5

2

4

2

3

2

2

2

1

2

0

MSb

LSb

MSb

LSb

Units:

6.25

ACR LSB

20m



15m



10m



5m



6.25

Vh

312.5

Ah

416.7

Ah

625

Ah

1.250mAh

ACR RANGE

20m



15m



10m



5m



±204.8mVh

±10.24Ah

±13.65Ah

±20.48Ah

±40.96Ah

OFFSET ACCUMULATION BLANKING

In order to avoid the accumulation of small positive offset errors over long periods, an offset blanking filter is

provided. The blanking filter is enabled by setting the OBEN bit in the Status Register. When OBEN is set, charge

currents (positive Current register values) between 15.625

V and 62.5V are not accumulated in the ACR.

the ACR.

ACCUMULATION BIAS

Systematic errors or an application preference can require the application of an arbitrary bias to the current

accumulation process. The Accumulation Bias register is provided to allow a user programmed constant positive or

negative polarity bias to the current accumulation process. The Accumulation Bias value can be used to estimate

battery currents that do not flow through the sense resistor, estimate battery self-discharge, or correct for offset

error in the Current register and ACR register. The user programmed two’s complement value in the Accumulation

Bias register is added to the Current Register once per current sample. The register format supports the

accumulation bias to be applied in 1.95

V increments over a ±250V range. When using a 20m sense resistor,

the bias control is 100

A over a ±12.5mA range.

The Accumulation Bias register is directly read and write accessible. The user value is made non-volatile with a

Copy Data command targeting EEPROM block 0. The Accumulation Bias register is loaded from EEPROM

memory on power up and a transition from Sleep to Active mode.

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