DS2792 Programmable Fuel Gauge with UART Interface

34 of 40

Current Measurement Bias

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

measurement process. The current measurement bias value sets a user-programmed positive or negative bias to

the current measurement. The current measurement 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

registers. The user-programmed two’s complement value is added to the current register once per current sample.

The bias control is applied in 0.98

PV increments over a ±125PV range. When using a 15m: sense resistor, the

bias control can be adjusted in 65.3

PA increments over a ±8.33mA range. The current measurement bias bit field is

located in the upper byte of the ADC configuration register.

Figure 19. Current Measurement Bias Field

Upper Byte of Word Address 600Ah

S

2

6

2

5

2

4

2

3

2

2

2

1

2

0

MSb

LSb

“S”: sign bit

Units: 2

Current Accumulation

Current measurements are internally accumulated and displayed in the accumulated current register (ACR). The

accuracy of the ACR is dependent on both the current measurement and the accumulation time base. The 16-bit

ACR has a range of ±204.8mVh with a resolution of 6.25µVh. Accumulation of charge current above the maximum

register value is reported at the maximum value; conversely, accumulation of discharge current below the minimum

register value is reported at the minimum value. Read and write access is allowed to the ACR.

Figure 20. Accumulated Current Register Format

Word Address 6006h

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

“S”: sign bit(s)

Units: 2

ACR RESOLUTION (1 LSB)

25mŸ

20mŸ

15mŸ

10mŸ

6.25µVh

0.25mAh

0.312mAh

0.416mAh

0.625mAh

ACR ACCUMULATION RANGE

25mŸ

20mŸ

15mŸ

10mŸ

±204.8mVh

±8.192Ah

±10.24Ah

±13.65Ah

±20.48Ah