DS2764 High-Precision Li+ Battery Monitor With 2-Wire Interface

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CURRENT OFFSET COMPENSATION

The current measurement and current accumulation are internally compensated for offset on a continual basis

minimizing error resulting from variations in device temperature and voltage. Additionally, the Current Offset Bias

register is a user programmable constant bias that can be used to alter the offset of the Current and Accumulated

current registers. User programmed bias values can be used to correct for offset errors after final assembly of the

module or pack. An offset value can be purposely chosen to bias current accumulation in the discharge polarity to

ensure a pessimistic accounting of

mA level standby currents.

The Current Offset Bias value resides in EEPROM address 33h in two’s-complement format and is subtracted from

current measurements during the accumulation process. The Current Offset Bias is applied to the internal and

external sense resistor configurations. The factory default for EEPROM address 33h is 0.

Figure 7. Current Offset Bias

Address 33

S

2

6

2

5

2

4

2

3

2

2

2

1

2

0

MSb

LSb

Units: 0.625mA for Internal Sense Resistor

15.625

mV for External Sense Resistor

VOLTAGE MEASUREMENT

register is updated in two’s-complement format every 3.4ms with a 4.88mV resolution. Voltages above the

maximum register value are reported as the maximum value. Figure 8 shows the voltage register format.

Figure 8. Voltage Register Format

MSB—Address 0C

LSB—Address 0D

S

2

9

2

8

2

7

2

6

2

5

2

4

2

3

2

2

2

1

2

0

X

X

X

X

X

MSb

LSb

MSb

LSb

Units: 4.88mV

TEMPERATURE MEASUREMENT

The DS2764 uses an integrated temperature sensor to continually measure battery temperature. Temperature

measurements are placed in the temperature register every 220ms in two’s-complement format with a 0.125°C

resolution over a

±127°C range. Figure 9 shows the temperature register format.

Figure 9. Temperature Register Format

MSB—Address 18

LSB—Address 19

S

2

9

2

8

2

7

2

6

2

5

2

4

2

3

2

2

2

1

2

0

X

X

X

X

X

MSb

LSb

MSb

LSb

Units: 0.125

°C