bq2016

GAS GAUGE IC FOR

HIGH DISCHARGE RATES

SLUS475A– JANUARY 2001 – REVISED NOVEMBER 2002

9

POST OFFICE BOX 655303

main gas gauge registers (continued)

NAC calibration

The bq2016 sets NAC to 85% of LMD when it detects a transition from fast-charge to a trickle charge provided

that 85%

≥ NAC > 80% of LMD when the bq2016 detects the transition. For this determination, fast-charge

detection (FCDT) corresponds to the FCDT value set by the PROG pin. Fast-charge detection occurs when the

FCDT condition is met for 30s after the CHGS bit is set in FLGS1. Once fast-charge activity is qualified, a

transition of the SRC signal below the FCDT threshold enables trickle-charge detection. The bq2016 verifies

trickle charge by continuing to sample the SRC input for signals above the trickle-charge threshold and below

the fast-charge threshold. This sampling can take up to 3 minutes. Once a trickle-charge is verified, the bq2016

adjusts NAC up to 85% of LMD if NAC was between 80% and 85% of LMD. If NAC was greater then 85% of

LMD, NAC is unchanged upon transition detection.

last measured discharge (LMD)

Last measured discharge is the most recent measured discharge capacity of the battery. On initialization, the

bq2016 sets LMD = PFC. When a valid charge is detected following a valid discharge, the bq2016 updates LMD

with the current value in DCR. During subsequent discharges, the bq2016 updates LMD with the current value

in DCR. (The DCR value represents the measured discharge capacity of the battery from full to the EDV

threshold.) The bq2016 limits the adjustment of LMD down to 75% of its previous value. A qualified discharge

is necessary for a capacity transfer from DCR to the LMD register. The LMD register also serves as the 100%

reference threshold used by the display mode.

discharge count register (DCR)

The discharge count register (DCR) is used to update the last measured discharge register only if a complete

battery discharge from full to empty occurs without any partial battery charges. In this way, the bq2016 adapts

its capacity determination based on the actual conditions of discharge.

The DCR counts up during discharge independent of NAC and can continue to increase after NAC decrements

to 0. Before NAC = 0 (empty battery), both discharge and self-discharge increment the DCR. After NAC = 0,

only discharge increments the DCR. The DCR resets to 0 when the VDQ bit in the primary status flags register

(FLAGS1) is set on charge. The bq2016 sets VDQ=1 on a fast charge-to-trickle detection if NAC is greater than

80% of LMD or 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 valid charge after a discharge to EDV threshold if the bq2016

detects a qualified discharge. A valid charge is a minimum of one (maximum of two) NAC increments. A qualified

discharge occurs if

bq2016 detects EDV on discharge.

The VDQ bit set to a one indicates whether the present discharge is valid for LMD update.

programming the bq2016

The bq2016 is programmed with the VPFC and the PROG pins. During power-up or initialization, the bq2016

reads the state of these multilevel inputs and latches in the programmable configuration settings. Resistor

divider networks for VPFC and PROG should target the nominal thresholds as defined in the programming

tables.