Datasheet

bq27510-G2

SLUS948 –AUGUST 2010

www.ti.com

Activities Upon Pack Insertion

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 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0

Configuration

Byte – – – – – – – LU_ PROF

(1)

(1) LU_PROF = Last profile used by gas gauge. Cell0. last used when cleared. Cell1 last used when set. Default is 0.

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.