BQ27620-G1 Datasheet, PDF (31/45 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge

bq27620-G1
www.ti.com
SLUSAE3 – OCTOBER 2012
Table 5-6. Pin Function Code Summary
PFC
0
1
2
3
PFC_CFG
[1:0]
0/0
0/1
1/0
1/1
External Thermistor Bias Rate
([TEMPS]=1 only)
Dis-
charge Charge
Sleep
1 / sec 1 / sec
1 / 20
sec
None
1 / sec
BAT_GD pin
Usage for PFC Pin Function Description
N/A
A dedicated external thermistor is used for the fuel gauge to monitor battery
temperature in all conditions. The BAT_GD pin is not used to interface with a charger
IC.
Temperature-
based Charge
Inhibit.
A dedicated external thermistor is used for the fuel gauge to monitor battery
temperature in all conditions. If battery charging temperature falls outside of the
preset range defined in data flash, a charger can be disabled via the BAT_GD pin
until cell temperature recovers. See Charge Inhibit and Suspend, for additional
details.
N/A
A shared external thermistor is supported between the fuel gauge and a charger IC;
however, the BAT_GD pin is not used to interface with the charger IC. The fuel gauge
will bias the thermistor for battery temperature measurement and BAT INSERT
CHECK mode (If OpConfig B [BIE] = 1) under discharge and relaxation conditions
only so the charger IC can separately bias the thermistor during charge mode.
Follows Flags( )
[FC] flags bit.
Used to disable a battery charger IC when fuel gauge has determined the battery is
fully charged. The BAT_GD pin reflects the logical status of the Flags( ) [FC] bit and
is typically connected directly to the charger's Charge Enable/Disable (CE/CD) pin or
via a network to drive the charger's Temperature Sense (TS) pin.
5.3.3 BAT_LOW Pin
The BAT_LOW pin provides a system processor with an electrical indicator of battery status. The signaling
on the BAT_LOW pin follows the status of the [SOC1] bit in the Flags( ) register. Note that the polarity of
the BAT_LOW pin can be inverted via the [BATL_POL] bit of Operation Configuration.
5.3.4 Power Path Control With the BAT_GD Pin
The bq27620-G1 must operate in conjunction with other electronics in a system appliance, such as
chargers or other ICs and application circuits that draw appreciable power. After a battery is inserted into
the system, there should be no charging current or a discharging current higher than C/20, so that an
accurate OCV can be read. The OCV is used for helping determine which battery profile to use, as it
constitutes part of the battery impedance measurement
When a battery is inserted into a system, the Impedance Track™ algorithm requires that no charging of
the battery takes place and that any discharge is limited to less than C/20—these conditions are sufficient
for the fuel gauge to take an accurate OCV reading. To disable these functions, the BAT_GD pin is merely
negated from the default setting. Once an OCV reading has be made, the BAT_GD pin is asserted,
thereby enabling battery charging and regular discharge of the battery. The Operation Configuration
[BATG_POL] bit can be used to set the polarity of the battery good signal, should the default configuration
need to be changed.
Figure 5-1 details how the BAT_GD pin functions in the context of battery insertion and removal, as
well as NORMAL vs. SLEEP modes.
In PFC 1, the BAT_GD pin is also used to disable battery charging when the bq27620-G1 reads
battery temperatures outside the range defined by [Charge Inhibit Temp Low, Charge Inhibit Temp
High]. The BAT_GD line is asserted once temperature falls within the range [Charge Inhibit Temp
Low + Temp Hys, Charge Inhibit Temp High – Temp Hys].
Copyright © 2012, Texas Instruments Incorporated
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FUNCTIONAL DESCRIPTION
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