BQ27620-G1 Datasheet, PDF (27/45 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge

bq27620-G1
www.ti.com
SLUSAE3 – OCTOBER 2012
5.2 IMPEDANCE TRACK™ VARIABLES
The bq27620-G1 has several data flash variables that permit the user to customize the Impedance
Track™ algorithm for optimized performance. These variables are dependent upon the power
characteristics of the application as well as the cell itself.
5.2.1 Load Mode
Load Mode is used to select either the constant-current or constant-power model for the Impedance
Track™ algorithm as used in Load Select (see Load Select). When Load Mode is 0, the Constant
Current Model is used (default). When 1, the Constant Power Model is used. The [LDMD] bit of
CONTROL_STATUS reflects the status of Load Mode.
5.2.2 Load Select
Load Select defines the type of power or current model to be used to compute load-compensated
capacity in the Impedance Track™ algorithm. If Load Mode = 0 (Constant-Current) then the options
presented in Table 5-1 are available.
Table 5-1. Constant-Current Model Used When Load Mode = 0
LoadSelect Value
0
1(default)
2
3
4
5
6
Current Model Used
Average discharge current from previous cycle: There is an internal register that records the average discharge
current through each entire discharge cycle. The previous average is stored in this register.
Present average discharge current: This is the average discharge current from the beginning of this discharge cycle
until present time.
Average current: based on EffectiveCurrent( )
Current: based off of a low-pass-filtered version of EffectiveCurrent( ) (τ =14 s)
Design capacity / 5: C Rate based off of Design Capacity /5 or a C/5 rate in mA.
AtRate (mA): Use whatever current is in AtRate( )
User_Rate-mA: Use the value in User_Rate-mA. This mode provides a completely user-configurable method.
If Load Mode = 1 (Constant Power) then the following options shown in Table 5-2 are available
Table 5-2. Constant-Power Model Used When Load Mode = 1
LoadSelect Value
0
1(default)
2
3
4
5
6
Power Model Used
Average discharge power from previous cycle: There is an internal register that records the average discharge power
through each entire discharge cycle. The previous average is stored in this register.
Present average discharge power: This is the average discharge power from the beginning of this discharge cycle
until present time.
Average current × voltage: based off the EffectiveCurrent( ) and Voltage( ).
Current × voltage: based off of a low-pass-filtered version of EffectiveCurrent( ) (τ=14 s) and Voltage( )
Design energy / 5: C Rate based off of Design Energy /5 or a C/5 rate in mA.
AtRate (10 mW): Use whatever value is in AtRate( ).
User_Rate-10mW: Use the value in User_Rate-10mW. This mode provides a completely user-configurable method.
5.2.3 Reserve Cap-mAh
Reserve Cap-mAh determines how much actual remaining capacity exists after reaching 0
RemainingCapacity( ), before Terminate Voltage is reached. A no-load rate of compensation is applied
to this reserve.
5.2.4 Reserve Cap-mWh
Reserve Cap-mWh determines how much actual remaining capacity exists after reaching 0
AvailableEnergy( ), before Terminate Voltage is reached. A no-load rate of compensation is applied to
this reserve capacity.
Copyright © 2012, Texas Instruments Incorporated
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FUNCTIONAL DESCRIPTION
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