BQ27520-G2 Datasheet, PDF (27/47 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated LDO

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bq27520-G2
SLUSAB7A – MARCH 2011 – REVISED AUGUST 2011
5.2.8 Qmax 0 and Qmax 1
Generically called Qmax, these dynamic variables contain the respective maximum chemical capacity of
the active cell profiles, and are determined by comparing states of charge before and after applying the
load with the amount of charge passed. They also correspond to capacity at a low rate of discharge, such
as the C/20 rate. For high accuracy, this value is periodically updated by the bq27520-G2 during
operation. Based on the battery cell capacity information, the initial value of chemical capacity should be
entered in the Qmax n field for each default cell profile. The Impedance Track™ algorithm updates these
values and maintains them the associated actual cell profiles.
5.2.9 Update Status 0 and Update Status 1
Bit 0 (0x01) of the Update Status n registers is updated as needed by the bq27520-G2 to indicate that
new Qmax parameters have been learned. The Update Status n registers are modified automatically by
the bq27520-G2 and TI's evaluation software during the process of creating a golden Data Flash file. The
remaining bits are reserved.
5.2.10 Avg I Last Run
The bq27520-G2 logs the current averaged from the beginning to the end of each discharge cycle. It
stores this average current from the previous discharge cycle in this register. This register should not be
modified. It is only updated by the bq27520-G2 when required.
5.2.11 Avg P Last Run
The bq27520-G2 logs the power averaged from the beginning to the end of each discharge cycle. It stores
this average power from the previous discharge cycle in this register. To get a correct average power
reading the bq27520-G2 continuously multiplies instantaneous current times Voltage( ) to get power. It
then logs this data to derive the average power. This register should not be modified. It is only updated by
the bq27520-G2 when required.
5.2.12 Delta Voltage
The bq27520-G2 stores the maximum difference of Voltage( ) during short load spikes and normal load,
so the Impedance Track™ algorithm can calculate remaining capacity for pulsed loads. It is not
recommended to change this value.
5.2.13 Default Ra and Ra Tables
These tables contain encoded data and, with the exception of the Default Ra Tables, are automatically
updated during device operation. No user changes should be made except for reading/writing the values
from a pre-learned pack (part of the process for creating golden image files).
5.3 DETAILED PIN DESCRIPTION
5.3.1 The Operation Configuration Register
Some bq27520-G2 pins are configured via the Operation Configuration data flash register, as indicated
in Table 5-3. This register is programmed/read via the methods described in Section 4.2.1, Accessing the
Data Flash. The register is located at subclass = 64, offset = 0.
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FUNCTIONAL DESCRIPTION
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