BQ27520-G2 Datasheet, PDF (35/47 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated LDO

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RSNS1
0
0
1
1
1
1
bq27520-G2
SLUSAB7A – MARCH 2011 – REVISED AUGUST 2011
Table 5-7. I_WAKE Threshold Settings⁽¹⁾ (continued)
RSNS0
IWAKE
Vth(SRP–SRN)
1
0
1.0 mV or –1.0 mV
1
1
2.2 mV or –2.2 mV
0
0
2.2 mV or –2.2 mV
0
1
4.6 mV or –4.6 mV
1
0
4.6 mV or –4.6 mV
1
1
9.8 mV or –9.8 mV
5.8.2 FLASH UPDATES
Data Flash can only be updated if Voltage( ) ≥ Flash Update OK Voltage. Flash programming current can
cause an increase in LDO dropout. The value of Flash Update OK Voltage should be selected such that
the bq27520-G2 V_CC voltage does not fall below its minimum of 2.4 V during Flash write operations.
5.9 AUTOCALIBRATION
The bq27520-G2 provides an autocalibration feature that measures the voltage offset error across SRP
and SRN as operating conditions change. It subtracts the resulting offset error from normal sense resistor
voltage, V_SR, for maximum measurement accuracy.
Autocalibration of the coulomb counter begins on entry to SLEEP mode, except if Temperature( ) is ≤ 5°C
or Temperature( ) ≥ 45°C.
The fuel gauge also performs a single offset when (1) the condition of AverageCurrent( ) ≤ 100 mA and (2)
{voltage change since last offset calibration ≥ 256 mV} or {temperature change since last offset calibration
is greater than 8°C for ≥ 60 s}.
Capacity and current measurements continue at the last measured rate during the offset calibration when
these measurements cannot be performed. If the battery voltage drops more than 32 mV during the offset
calibration, the load current has likely increased; hence, the offset calibration is aborted.
6 APPLICATION-SPECIFIC INFORMATION
6.1 BATTERY PROFILE STORAGE AND SELECTION
6.1.1 Common Profile Aspects
When a battery pack is removed from host equipment, the bq27520-G2 maintains some of the battery
information in case the battery is re-inserted. This way, the Impedance Track™ algorithm has a means of
recovering battery-status information, thereby maintaining good state-of-charge (SOC) estimates.
Two default battery profiles are available to store battery information. They are used to provide the
Impedance Track™ algorithm with the default information on two possible battery types expected to be
used with the end-equipment. These default profiles can be used to support batteries of different
chemistry, same chemistry but different capacities, or same chemistry but different models. Default
profiles are programmed by the end-equipment manufacturer. However, only one of the default profiles
can be selected, and this selection cannot be changed during end-equipment operation.
In addition to the default profiles, the fuel gauge maintains two profiles PACK0 and PACK1. These tables
hold dynamic battery data, and keep track of the status for up to two of the most recent batteries used. In
most cases, the fuel gauge can manage the information on two removable battery packs.
Copyright © 2011, Texas Instruments Incorporated
APPLICATION-SPECIFIC INFORMATION
35
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