BQ2011 datasheet(7/20 Pages) TI

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Nominal Available Charge (NAC):

NAC counts up during charge to a maximum value

of LMD and down during discharge and self dis-

charge to 0. NAC is reset to 0 on initialization and

on the first valid charge following discharge to EDV.

To prevent overstatement of charge during periods

of overcharge, NAC stops incrementing when NAC

= LMD.

Note: NAC is set to the value in LMD when SEG5

is pulled low during a reset.

Discharge Count Register (DCR):

The DCR counts up during discharge independent

of NAC and could continue increasing after NAC

has decremented to 0. Prior to NAC = 0 (empty

battery), both discharge and self-discharge incre-

ment the DCR. After NAC = 0, only discharge in-

crements the DCR. The DCR resets to 0 when NAC

= LMD.

The DCR does not roll over but stops

counting when it reaches FFFFh.

The DCR value becomes the new LMD value on the

first charge after a valid discharge to VEDV if:

No valid charge initiations (charges greater than

256 NAC counts; or 0.006 – 0.01C) occurred dur-

ing the period between NAC = LMD and EDV

detected.

The self-discharge count is not more than 4096

counts (8% to 18% of PFC, specific percentage

threshold determined by PFC).

The temperature is

≥ 0°C when the EDV level is

reached during discharge.

The valid discharge flag (VDQ) indicates whether

the present discharge is valid for LMD update.

Charge Counting

Charge activity is detected based on a negative voltage

on the VSR input.

If charge activity is detected, the

bq2011 increments NAC at a rate proportional to VSRO

(VSR +VOS) and, if enabled, activates an LED display

if VSRO < -1mV. Charge actions increment the NAC af-

ter compensation for charge rate and temperature.

The bq2011 determines a valid charge activity sustained

at a continuous rate equivalent to VSRO < -400

µV. A

valid charge equates to a sustained charge activity

greater than 256 NAC counts. Once a valid charge is de-

tected, charge counting continues until VSRO rises

above -400

µV.

Discharge Counting

All discharge counts where VSRO > 500

µV cause the

NAC register to decrement and the DCR to increment.

Exceeding the fast discharge threshold (FDQ) if the rate

is equivalent to VSRO > 2mV activates the display, if en-

abled. The display becomes inactive after VSRO falls be-

low 2mV.

Self-Discharge Estimation

The bq2011 continuously decrements NAC and incre-

ments DCR for self-discharge based on time and tempera-

ture. The self-discharge count rate is programmed to be a

nominal 1

* NAC rate per day. This is the rate for a bat-

tery whose temperature is between 20°–30°C. The NAC

Count Compensations

The bq2011 determines fast charge when the NAC up-

dates at a rate of

≥2 counts/sec. Charge and discharge

activity is compensated for temperature and charge/dis-

charge rate before updating the NAC and/or DCR. Self-

discharge estimation is compensated for temperature

before updating the NAC or DCR.

Charge Compensation

Two charge efficiency factors are used for trickle charge

and fast charge.

Fast charge is defined as a rate of

charge resulting in

≥ 2 NAC counts/sec (≥ 0.15C to 0.32C

depending on PFC selections; see Table 2). The compen-

sation defaults to the fast charge factor until the actual

charge rate is determined.

Temperature adapts the charge rate compensation fac-

tors over three ranges between nominal, warm, and hot

temperatures. The compensation factors are shown below.

bq2011

Charge

Temperature

Trickle Charge

Compensation

Fast Charge

Compensation

<40°C

0.80

0.95

≥ 40°C

0.75

0.90

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