DS2786 Stand-Alone OCV-Based Fuel Gauge

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CURRENT RESOLUTION (1 LSB)

20m



15m



10m



5m



25

V

1.25mA

1.667mA

2.5mA

5mA

CURRENT INPUT RANGE

20m



15m



10m



5m



±51.2mV

±2.56A

±3.41A

±5.12A

±10.24A

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 and detection of an OCV

condition. 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 25

V steps to any value between +3.175mV

and -3.2mV. The COBR value is stored as a two’s complement value in nonvolatile (NV) memory. The COBR

factory default value is 00h.

Figure 9. Current Offset Bias Register Format

Address 60h

S

2

6

2

5

2

4

2

3

2

2

2

1

2

0

MSb

LSb

“S”: sign bit

Units:

25

CURRENT ACCUMULATION

An Internal Accumulated Current Register (IACR) serves as an up/down counter holding a running count of charge

since the last OCV condition. Current measurement results, plus a programmable bias value are internally

summed, or accumulated, at the completion of each current measurement conversion period. The IACR has a

range of ±204.8mVh. The IACR uses the Initial or Learned Cell Capacity Registers to increment or decrement the

Relative Capacity Register as current flows into or out of the battery. In this way, the fuel gauge is accurate even

when an OCV condition does not occur for an extended time period.

IACR RANGE

20m



15m



10m



5m



±204.8mVh

±10.24Ah

±13.65Ah

±20.48Ah

±40.96Ah