bq2016

GAS GAUGE IC FOR

HIGH DISCHARGE RATES

SLUS475A– JANUARY 2001 – REVISED NOVEMBER 2002

7

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

functional description (continued)

current

The SRC input of the bq2016 measures battery charge and discharge current. The SRC ADC input converts

the current signal from the series sense resistor every 2 seconds and stores the result in the current scale

register (VSRH:L). The full scale input range to SRC is limited to

±250 mV as shown in Table 1.

Table 1. SRC Input Range

SENSE RESISTOR

(m

Ω)

FULL SCALE INPUT

(

±A)

5

50

7.5

33

10

25

temperature

The bq2016 measures temperature, either with its internal thermistor or with an external thermistor, depending

on the state of the PROG input. The bq2016 accepts an external NTC thermistor on the TS input. The bq2016

samples the TS input voltage every 2 seconds and stores the voltage in the TS Input Voltage (TEMPVH:L)

register and the actual temperature in the temperature (TEMP) register. With an external thermistor, the bq2016

develops the temperature value for the temperature register on the basis of a Semitec 103AT (10K) NTC model.

The bq2016 reports the temperature in 1

°C steps with an accuracy of 4°C or 6°C for an external and internal

thermistor, respectively. The temperature reading is used to adapt remaining capacity for charge and discharge

efficiency and to adjust for the battery’s self discharge.

If an internal thermistor is selected for temperature measurement, the TS input should be grounded.

THON may be used to connect the bias source to the thermistor when the bq2016 samples the TS input. THON

is high impedance when the temperature is measured, and driven low otherwise.

gas gauge operation

general

The operational overview diagram in Figure 5 illustrates the operation of the bq2016. The bq2016 accumulates

a measure of charge and discharge currents and estimates self-discharge. The bq2016 compensates the

charge and discharge currents for rate and temperature efficiencies. It also adjusts the self-discharge estimation

for temperature variation. The bq2016 stores the compensated charge accumulation in the nominal available

capacity (NAC) register. For LED indication, the bq2016 adjusts NAC for the battery pack operating

temperature.

The discharge count register (DCR) tracks discharge activity of the battery. The last measured discharge (LMD)

represents the discharge capacity or learned full capacity of the battery in the application. The bq2016 transfers

the value in DCR to LMD when a qualified discharge occurs.