AN3064

Battery monitoring functions

Doc ID 16263 Rev 1

9/15

2.4

Battery voltage and temperature reading

The battery voltage and chip temperature (close to the battery temperature) are measured

by means of an A/D converter and a multiplexer. This function takes place concurrently to

the Coulomb counter function with a dedicated A/D converter, which means that it does not

affect the performance of the Coulomb counter. To reduce the power consumption, a

conversion takes place every two seconds only, alternating between the battery voltage and

temperature (so each value is refreshed every four seconds).

The voltage code is a 12-bit binary number using the two’s complement binary format. Bit 11

is the sign bit and bits 0 to 10 are the data bits. The LSB value (bit 0) is 2.44 mV. Note that

although the input voltage range is limited to a positive voltage, negative voltage codes can

be read when the input voltage is close to 0 V due to internal offset effects.

The temperature code is a 12-bit binary number using the two’s complement binary format.

Bit 11 is the sign bit and bits 0 to 10 are the data bits. The LSB value (bit 0) is 0.125° C.

The actual values of the voltage and temperature are:

●

voltage (mV) = Voltage_code * 2.44.

●

temperature (°C) = Temperature_code * 0.125.

The VTM_EOC bit in the REG_CTRL register can be used to check that at least one new

measurement of the voltage or temperature has been done since the last reading of the

REG_CTRL register.

Table 7.

REG_VOLTAGE_LOW. address 8 (08h)

Name

Pos.

Type

Power-up

Description

DATA[7..0]

[7..0]

R

00

Battery voltage data

Table 8.

REG_VOLTAGE_HIGH. address 9 (09h)

Name

Pos.

Type

Power-up

Description

DATA[11..8]

[3..0]

R

0

Battery voltage data

DATA[15..12]

[7..4]

R

0

unused

Table 9.

REG_TEMPERATURE_LOW. address 10 (0Ah)

Name

Pos.

Type

Power-up

Description

DATA[7..0]

[7..0]

R

00

Temperature data

Table 10.

REG_TEMPERATURE_HIGH. address 11 (0Bh)

Name

Pos.

Type

Power-up

Description

DATA[11..8]

[3..0]

R

0

Temperature data

DATA[15..12]

[7..4]

R

0

unused