BQ2012 datasheet(13/20 Pages) TI

13 / 20 page

The EDVF values are:

Where EDVF is:

Valid charge action detected, VSB

≥ 0.95V

1VSB < 0.95V providing that OVLD=0 (see

FLGS2 register description)

Temperature and Gas Gauge Register

(TMPGG)

The read-only TMPGG register (address=02h) contains

two data fields. The first field contains the battery tem-

perature. The second field contains the available charge

from the battery.

The bq2012 contains an internal temperature sensor.

The temperature is used to set charge and discharge ef-

ficiency factors as well as to adjust the self-discharge co-

efficient.

The temperature register contents may be translated as

shown in Table 7.

The bq2012 calculates the available charge as a function

of NAC, temperature, and a full reference, either LMD

or PFC. The results of the calculation are available via

the display port or the gas gauge field of the TMPGG

in 1

16 increments from 0 to

16.

The gas gauge display and the gas gauge portion of the

TMPGG register are adjusted for cold temperature de-

pendencies. A piece-wise correction is performed as fol-

lows:

The adjustment between > 0°C and -20°C<T<0°C has

a 10°C hysteresis.

Nominal Available Charge Registers

(NACH/NACL)

The read/write NACH high-byte register (address=03h)

and the read-only NACL low-byte register (address=17h)

are the main gas gauging register for the bq2012. The

NAC registers are incremented during charge actions and

decremented during discharge and self-discharge actions.

The correction factors for charge/discharge efficiency are

applied automatically to NAC.

On reset, if PROG6 = Z or low, NACH and NACL are

cleared to 0; if PROG6 = high, NACH = PFC and NACL

= 0. When the bq2012 detects a valid EDV1, NACH and

NACL are reset to 0. Writing to the NAC registers affects

the available charge counts and, therefore, affects the

bq2012 gas gauge operation. Do not write the NAC regis-

ters to a value greater than LMD.

Battery Identification Register (BATID)

The read/write BATID register (address=04h) is avail-

able for use by the system to determine the type of bat-

tery pack. The BATID contents are retained as long as

VCC is greater than 2V. The contents of BATID have no

effect on the operation of the bq2012. There is no de-

fault setting for this register.

Last Measured Discharge Register (LMD)

LMD is a read/write register (address=05h) that the

bq2012 uses as a measured full reference. The bq2012

adjusts LMD based on the measured discharge capacity

bq2012

Temperature

Available Capacity Calculation

> 0°C

NAC / “Full Reference”

-20°C < T < 0°C

0.75 * NAC / “Full Reference”

< -20°C

0.5 * NAC / “Full Reference”

TMP3

TMP2

TMP1

TMP0

Temperature

0000

T < -30°C

0001

-30°C < T < -20°C

0010

-20°C < T < -10°C

0011

-10°C < T < 0°C

0100

0°C < T < 10°C

0101

10°C < T < 20°C

0110

20°C < T < 30°C

0111

30°C < T < 40°C

1000

40°C < T < 50°C

1001

50°C < T < 60°C

1010

60°C < T < 70°C

1011

70°C < T < 80°C

1100

T > 80°C

Table 7. Temperature Register Translation

TMPGG Temperature Bits

3210

TMP3

TMP2

TMP1

TMP0

TMPGG Gas Gauge Bits

GG3

GG2

GG1

GG0

FLGS1 Bits

EDVF

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