BQ27510_08 Datasheet, PDF (28/36 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Direct Battery Connection

bq27510
SLUS816A – MARCH 2008 – REVISED JUNE 2008.......................................................................................................................................................... www.ti.com
RSNS1
0
0
0
0
1
1
1
1
Table 11. I_WAKE Threshold Settings⁽¹⁾
RSNS0
IWAKE
Vth(SRP-SRN)
0
0
Disabled
0
1
Disabled
1
0
+1.25 mV or –1.25 mV
1
1
+2.5 mV or –2.5 mV
0
0
+2.5 mV or –2.5 mV
0
1
+5 mV or–5 mV
1
0
+5 mV or –5 mV
1
1
+10 mV or –10 mV
(1) The actual resistance value versus the setting of the sense resistor is not important; just the actual
voltage threshold when calculating the configuration.
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 bq27510
Vcc voltage does not fall below its minimum of 2.4V during Flash write operations.
AUTOCALIBRATION
The bq27510 provides an autocalibration feature that will measure the voltage offset error across SRP and SRN
from time-to-time as operating conditions change. It subtracts the resulting offset error from normal sense
resistor voltage, VSR, for maximum measurement accuracy.
Autocalibration of the ADC 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( ) ≤ 100mA and (2)
{voltage change since last offset calibration ≥ 256mV} or {temperature change since last offset calibration is
greater than 80°C for ≥ 60s}.
Capacity and current measurements will continue at the last measured rate during the offset calibration when
these measurements cannot be performed. If the battery voltage drops more than 32mV during the offset
calibration, the load current has likely increased considerably; hence, the offset calibration will be aborted.
APPLICATION-SPECIFIC INFORMATION
BATTERY PROFILE STORAGE AND SELECTION
Common Profile Aspects
When a battery pack is removed from system equipment that implements the bq27510, the fuel gauge maintains
some of the battery information, in case it is re-inserted. This way the Impedance Track™ algorithm often has a
means of recovering battery-status information, thereby maintaining good state-of-charge (SOC) estimates.
The default battery profiles are available to store battery information. They are used to provide the Impedance
Track™ algorithm with the default information on the battery type expected to be used with the end-equipment.
The default profiles can be used to support batteries of same chemistry but different capacities. Default profiles
are programmed by the end-equipment manufacturer. 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 bq27510 maintains two active profiles: Cell0 and Cell1. 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 bq27510 can administrate information on two removable battery packs.
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