ds2786 Maxim Integrated Products, Inc., ds2786 Datasheet - Page 11

• Manufacturer Part Number: ds2786
• Description: Ds2786 Standalone Ocv-based Fuel Gauge
• Manufacturer: Maxim Integrated Products, Inc.

Figure 10. Relative Capacity Register Format
Prior to the first Learn operation, the Relative Capacity value is calculated by adding the IACR multiplied by the
Initial Capacity Scaling Factor (7Ah) to the Last OCV Relative Capacity (16h). After the first Learn operation, the
Relative Capacity value is calculated by adding the IACR multiplied by the Learned Capacity Scaling Factor (17h)
to the Last OCV Relative Capacity (16h).
Each Capacity Scaling Factor Register has a resolution of 78.125%/Vh and a maximum range of 0 to
19921.875%/Vh. During assembly, the Initial Capacity Register should be programmed to the capacity of the cell.
For example, an application using a 1Ah cell and 0.015Ω sense resistor would set the Initial Capacity Register to a
value of (100% ÷ (1Ah × 0.015Ω)) ÷ 78.125%/Vh = 55h. The Learned Capacity Scaling Factor Register is
controlled by the DS2786. The power up value is 00h, and the register is updated with the calculated new cell
capacity value after every Learn operation.
Figure 11. Initial Capacity Scaling Factor Register Format
Figure 12. Learned Capacity Scaling Factor Register Format
OCV DETECTION AND CURRENT BLANKING
The Blanking/OCV Threshold Register sets the current measurement level at which the DS2786 switches between
coulomb counting and open-circuit voltage measurement. When the magnitude of the measured current (after
COBR is applied) is less than the value defined by the Blanking/OCV Threshold Register, the measurement is not
summed into the IACR. Instead, the IACR is maintained at its present value and the DS2786 begins dV/dt
measurement evaluation to detect an OCV voltage condition. A threshold value that is below the minimum
operational current, but above the maximum idle current of the application should be selected. The Blanking/OCV
Threshold Register has a resolution of 25μV/R
default value is 06h
MSb
MSb
MSb
2
2
2
7
7
7
2
2
2
6
6
6
SNS
2
2
2
, and a range from 0mV/R
5
5
5
11 of 22
Address 7Ah
Address 02h
Address 17h
2
2
2
4
4
4
2
2
2
3
3
3
Units: 78.125%/Vh
Units: 78.125%/Vh
2
2
2
2
2
2
Units: 0.5%
2
2
2
1
1
1
LSb
LSb
LSb
2
2
2
SNS
0
0
0
to 6.375mV/R
SNS
. The factory