BQ27000_07 Datasheet, PDF (11/33 Pages) Texas Instruments – SINGLE CELL Li-Ion AND Li-Pol BATTERY GAS GAUGE IC FOR PORTABLE APPLICATIONS (bqJUNIOR)

bq27000, bq27200
www.ti.com
SLUS556D – SEPTEMBER 2004 – REVISED MARCH 2006
FUNCTIONAL DESCRIPTION (continued)
A learning cycle can be disqualified by any of the following conditions:
1. Cold temperature: Temperature ≤ TCOMP[3:0] (°C) when the EDV1 threshold voltage is reached.
2. Light load: A capacity learning cycle is disqualified if average current is less than or equal to 2 times the
initial standby load when the EDV1 threshold voltage is reached.
3. Fast voltage drop: VOLT ≤ (EDV1 – 256 mV) before EDV1 is set.
4. Excessive charging: Cumulative Charge > 255 NAC counts (910 µVh) during a learning discharge cycle
(alternating discharge/charge/discharge before EDV1 is set).
5. Reset: VDQ is cleared on all resets.
6. Excessive self-discharge: NAC reduction from self-discharge estimate (0.195%) performed 64 times.
7. Self-discharge at termination of learning cycle. If self-discharge estimate causes NAC ≤ LMD/16, VDQ is
cleared.
NAC is adjusted by charge and discharge coulometric measurements except when battery full or empty
conditions are detected. NAC = LMD is forced when IMIN = 1 (full detection) unless Temperature ≤ TCOMP[3:0]
(°C). During a discharge with VDQ = 1, NAC is not allowed to drop below LMD/16 until EDV1 = 1. If EDV1 = 1
occurs when NAC > LMD/16, NAC = LMD/16 will be forced. NAC = 0 is forced if EDVF = 1.
INPUTS
Charge
Current
Discharge
Current
Self−Discharge
Timer
Temperature
Compensation
+_ _
COMPUTATIONS ^{Nominal Available}
Charge (NAC)
OUTPUTS
Rate and
Temperature
Compensation
Compensated
Available Charge
_+ ₊
Last Measured
Discharge (LMD)
Qualified
Transfer
Learning Count
Register (LCR)
Temperature, Voltage,
Average Current,
Other Data
I²C or HDQ Interface
Figure 4. Operational Overview
UDG−03042
Register Interface
The bqJUNIOR stores all calculated information in RAM, which is backed up by the voltage on the RBI input.
EEPROM registers store permanent user data. The memory map for bq27000/bq27200 is shown in Table 1.
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