BQ27210 Datasheet, PDF (16/30 Pages) Texas Instruments – Li-Ion AND Li-Pol BATTERY GAS GAUGE IC FOR PORTABLE APPLICATIONS (bqJUNIOR)

bq27010, bq27210
SLUS707B – APRIL 2006 – REVISED JANUARY 2007
www.ti.com
Nominal Available Capacity Registers (NACL/NACH) — Address 0x0C/0x0D
This register pair reports the light-load, or uncompensated, capacity available from the battery. NAC increments
during charge (V_SRP > V_SRN) if Voltage > EDVF threshold and decrements during discharge (V_SRP < V_SRN). The
NAC registers are cleared by a reset if RAM corruption is detected. The register value is retained after a reset if
RAM corruption is not detected. The host system has read-only access to this register pair. NAC is reported in
units of 3.57 µVh per count.
Last Measured Discharge Registers (LMDL/LMDH) – Address 0x0E/0x0F
This register pair reports the light load, or uncompensated, capacity available from the battery when fully
charged. This value is updated after a valid learning cycle, which occurs when the battery is discharged from
fully charged (NAC = LMD) until the EDV1 voltage threshold is detected (EDV1 = 1) without any learning cycle
disqualifying event (VDQ = 1 during entire discharge). LMD will be updated with the measured capacity removed
from the battery during the discharge until the EDV1 threshold is reached plus 6.25% of design capacity (the
unmeasured capacity from EDV1 until the EDVF zero capacity threshold voltage) plus the computed capacity
compensation reduction due to discharge rate, temperature, and age. The host system has read-only access to
this register pair. LMD is reported in units of 3.57 µVh per count.
Compensated Available Capacity (CACL/CACH) – Address 0x10/0x11
This register pair reports the available capacity in the battery at the present discharge rate, temperature, and
age. CAC is equal to NAC minus the capacity compensation reduction based on the compensation coefficients
programmed in DCOMP (discharge compensation coefficients), TCOMP (temperature compensation
coefficients), and GAF/DEDV (gain age compensation coefficient). All compensations are impedance-based and
CAC will equal NAC at very low currents. However, CAC is not allowed to increase as long as there is no
charging current. If the discharge load is reduced, CAC may stop decrementing even though NAC continues to
decrement. When NAC drops sufficiently that the NAC minus CAC difference is equal to the discharge
compensation at the reduced load current, CAC will again start decrementing. CAC will equal NAC when
charging. The host system has read-only access to this register pair. CAC is reported in units of 3.57 µVh per
count.
Fully-Charged Compensated Available Capacity (FCACL/FCACH) – Address 0x12/0x13
This register pair reports the fully-charged capacity of the battery at the present discharge rate, temperature, and
age. FCAC is equal to LMD minus the capacity compensation reduction based on the compensation coefficients
programmed in DCOMP (discharge compensation coefficients), TCOMP (temperature compensation
coefficients), and GAF/DEDV (gain age compensation coefficient). All compensations are impedance-based and
FCAC will converge to LMD as the measured discharge current approaches zero. FCAC will equal LMD when
charging. The host system has read-only access to this register pair. FCAC is reported in units of 3.57 µVh per
count.
Average Current Registers (AIL/AIH) — Address 0x14/0x15
This register pair reports the magnitude of the average current through the sense resistor. The value is reported
with a resolution of 3.57 µV per count. Use the following equation to convert the value to mA, where R_S is the
sense resistor value in milliohms:
Average Current = (256 * AIH + AIL) * 3.57 / R_S
The current reported is an average over the last 5.12 seconds. The host system has read-only access to this
register pair.
Time-to-Empty Registers (TTEL/TTEH) — Address 0x16/0x17
This register pair reports calculated time-to-empty at the measured discharge rate. This value is based on the
temperature and discharge rate compensated available charge and the average current. The equation to
calculate TTE is:
TTE = 60 * CAC / AI
TTE is reported in minutes. The host system has read-only access to this register pair.
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