BQ2014SN datasheet(13/22 Pages) TI

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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 bq2014 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 bq2014 calculates the available charge as a function

of NAC, temperature, and LMD. The results of the cal-

culation are available via the display port or the gas

gauge field of the TMPGG register. The register is used

to give available capacity 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 Register

(NACH/NACL)

The read/write NACH register (address=03h) and the

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

main gas gauging registers for the bq2014. The NAC

registers are incremented during charge actions and

decremented during discharge and self-discharge ac-

tions. The correction factors for charge/discharge effi-

ciency are applied automatically to NAC.

On reset, NACH and NACL are cleared to 0. When the

bq2014 detects a charge, NACL resets to 0. NACH and

NACL are reset to 0 on the first valid charge after VSB =

EDV1. Writing to the NAC registers affects the available

charge counts and, therefore, affects the bq2014 gas

gauge operation. Do not write the NAC registers 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 bq2014. There is no de-

fault setting for this register.

Last Measured Discharge Register (LMD)

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

bq2014 uses as a measured full reference. The bq2014

adjusts LMD based on the measured discharge capacity

of the battery from full to empty. In this way the bq2014

updates the capacity of the battery. LMD is set to PFC

during a bq2014 reset.

Secondary Status Flags Register (FLGS2)

The read-only FLGS2 register (address=06h) contains

the secondary bq2014 flags.

The charge rate flag (CR) is used to denote the fast

charge regime.

Fast charge is assumed whenever a

charge action is initiated. The CR flag remains asserted

if the charge rate does not fall below 2 counts/sec.

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 Gas Gauge Bits

GG3

GG2

GG1

GG0

TMPGG Temperature Bits

3210

TMP3

TMP2

TMP1

TMP0

bq2014

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