BQ26501_16 Datasheet, PDF (12/33 Pages) Texas Instruments – HANDHELD APPLICATIONS

bq26501
Not Recommended For New Designs
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SLUS586B − OCTOBER 2003 − REVISED MARCH 2004
APPLICATION INFORMATION
At Rate Registers (ARH/ARL) − Address 0x02/0x03
For the bq26501, the host writes the current value to this register for predictive calculation of time-to-empty. The
device uses this value to predict the time-to-empty at any desired current. The current value written into this
register pair is always assumed to be a discharge current. The value written to AR should be the predicted
voltage across the sense resistor expressed in units of 3 µV per count.
This register is also used during pack manufacturing to input a nominal available charge (NAC) value to set the
NAC registers to the approximate initial pack capacity value.
At Rate Time to Empty Registers (ARTTEL/ARTTEH) − Address 0x04/0x05
Predicted time-to-empty, in minutes, at user entered discharge rate. The discharge current used in the
calculation is entered by the host system in the at-rate (AR) registers. The at-rate capacitance (ARCAP) value
used may be larger or smaller than CACT. It is computed using the same formulas as CACT, except the
discharge compensation is computed using AR, instead of average discharge current (AI), for the discharge
rate. The equation used to predict at rate time-to-empty is:
ARTTE + 60
ARCAP
AR
(1)
The host system has read only access to this register pair.
Reported Temperature Registers (TEMPL/TEMPH) − Address 0x06/0x07
The TEMPH and the TEMPL registers contain the reported die temperature. The temperature is expressed in
units of 0.25°K per count and updated every 2 seconds. The equation to calculate reported pack temperature
is:
T_PACK + 0.25 (256 TEMPH ) TEMPL)
(2)
The host system has read-only access to this register pair.
Reported Battery Voltage Registers (VOLTL/VOLTH) − Address 0x08/0x09
The VOLTH and the VOLTL low-byte registers contain the reported battery voltage measured on the BAT pin.
Voltage is expressed in mV and is updated every two seconds. Reported voltage cannot exceed 5000 mV. The
host system has read only access to this register pair.
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