BQ2011 datasheet(13/20 Pages) TI

13 / 20 page

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

4°C hysteresis.

Nominal Available Charge Register (NAC)

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

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

gas gauging registers for the bq2011. The NAC registers

are incremented during charge actions and decremented

during discharge and self-discharge actions. The correc-

tion factors for charge/discharge efficiency are applied

automatically to NAC.

On reset, the NACH and NACL registers are cleared to

zero. NACL stops counting when NACH reaches zero.

When the bq2011 detects a valid charge, NACL resets to

zero; writing to the NAC register affects the available

charge counts and, therefore, affects the bq2011 gas

gauge operation.

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 bq2011. There is no de-

fault setting for this register.

Last Measured Discharge Register (LMD)

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

bq2011 uses as a measured full reference. The bq2011

adjusts LMD based on the measured discharge capacity

of the battery from full to empty. In this way the bq2011

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

during a bq2011 reset.

Secondary Status Flags Register (FLGS2)

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

the secondary bq2011 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.

The CR values are:

Where CR is:

When charge rate falls below 2 counts/sec

When charge rate is above 2 counts/sec

The fast charge regime efficiency factors are used when

CR = 1. When CR = 0, the trickle charge efficiency fac-

tors are used. The time to change CR varies due to the

user-selectable count rates.

The discharge rate flags, DR2–0, are bits 6–4.

They are used to determine the present discharge re-

gime as follows:

The overload flag (OVLD) is asserted when a discharge

overload is detected, VSRD > 50mV. OVLD remains as-

serted as long as the condition persists and is cleared

when VSRD < 50mV.

DR2–0 and OVLD are set based on the measurement of the

voltage at the SR pin relative to VSS. The rate at which

this measurement is made varies with device activity.

bq2011

FLGS2 Bits

3210

DR2

DR1

DR0

DR2

DR1

DR0

VSR (V)

VSR < 50mV

50mV < VSR < 100mV

(overload, OVLD=1)

100mV < VSR < 150mV

150mV < VSR < 253mV

VSRD > 253mV

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”

FLGS2 Bits

OVLD

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