BQ27510-G2 Datasheet, PDF (30/38 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Direct Battery Connection

bq27510-G2
SLUS948 – AUGUST 2010
Activities Upon Pack Insertion
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First OCV and Impedance Measurement
At power-up the BAT_LOW/BAT_GD pin is inactive, so that the system cannot obtain power from the battery
(this depends on actual implementation). In this state, the battery is put in an open-circuit condition. Next, the
bq27510-G2 measures its first open-circuit voltage (OCV) via the BAT pin. From the OCV(SOC) table, the SOC
of the inserted battery is found. Then the BAT_LOW/BAT_GD pin is made active, and the impedance of the
inserted battery is calculated from the measured voltage and the load current: Z(SOC) = ( OCV(SOC) – V ) / I.
This impedance is compared with the impedance of the dynamic profiles, Packn, and the default profiles, Defn,
for the same SOC (the letter n depicts either a 0 or 1).
Reading Application Status
The Application Status data flash location contains cell profile status information, and can be read using the
ApplicationStatus( ) Extended Command (0x6a). The bit configuration of this function/location is shown in
Table 13.
Table 13. ApplicationStatus( ) Bit Definitions
Application
Configuration
Byte
bit7
bit6
bit5
bit4
bit3
bit2
bit1
–
–
–
–
–
–
–
(1) LU_PROF = Last profile used by gas gauge. Cell0. last used when cleared. Cell1 last used when set. Default is 0.
bit0
LU_ PROF⁽¹⁾
APPLICATION-SPECIFIC FLOW AND CONTROL
The bq27510-G2 supports only one type of battery profile. This profile is stored in both the Def0 and Def1
profiles. When a battery pack is inserted for the first time, the default profile is copied into the Packn profiles.
Then the Impedance Track™ algorithm begins gas gauging, regularly updating Packn as the battery is used.
When an existing pack is removed from the bq27510-G2 and a different (or same) pack is inserted, cell
impedance is measured immediately after battery detection. The bq27510-G2 chooses the profile which is
closest to the measured impedance, starting with the Packn profiles. That is, if the measured impedance
matches Pack0, then the Pack0 profile is used. If the measured impedance matches Pack1, then the Pack1
profile is used. If the measured impedance does not match the impedance stored in either Pack0 or Pack1, the
battery pack is deemed new (none of the previously used packs). Either Def0/Def1 profile is copied into either
the Pack0 or Pack1 profile, overwriting the oldest Packn profile.
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