DS2792 Programmable Fuel Gauge with UART Interface

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Figure 24. Vx Absolute Voltage Register Format

Word Address 6001h

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

“S”: sign bit

Units: 2

Temperature Measurement

The DS2792 uses an integrated temperature sensor to continually measure battery temperature. Temperature

measurements are updated in the temperature register every 220ms in two’s complement format with a resolution

of 0.125°C over a

r127°C range. The temperature register format is shown in Figure 25.

Figure 25. Temperature Register Format

Word Address 6005h

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

“S”: sign bit

Units: 2

qC

ADC Configuration Register

The ADC configuration register located at word address 600Ah controls current measurement bias and offset

blanking. ADC configuration register bits are read and write accessable by application code. IBIAS bits are

described in the current measurement bias section above. Offset blanking is controlled by the OBEN bit. If offset

blanking is enabled, the DS2792 assumes small positive currents do not occur in the application. Small positive

readings are considered A/D measurement error and are not accumulated.

Figure 26. ADC Configuration Register Format

ADDRESS

600Ah

BIT DEFINITION

Field

Bit

Format

Allowable Values

IBIAS

15:8

R/W

Current Measurement Bias

8-bit two’s complement value that is added to the current

measurement on every update.

Reserved

7:1

Read Only

Undefined

OBEN

0

R/W

Offset Blanking Enable

0 = All current measurements are accumulated into the ACR.

accumulated into the ACR.

PASSWORD-PROTECTED USER TRIM

System software can change current measurement gain, power-up state of the UART, and undervoltage threshold

of the IC through the user trim in program EEPROM (word addresses 001Eh–001Fh). The user trim values are

enabled through the trim key in the lower byte of address 001Fh. If the trim key is set to 76h, the user-trim values

replace the default trim values, if the trim key is set to any other value, default trim is selected. Note that either all

user-trim values are enabled or none are enabled. Figure 27 shows the format of all values that can be adjusted

and their default trim values.