BQ27520-G2 Datasheet, PDF (30/47 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated LDO

bq27520-G2
SLUSAB7A – MARCH 2011 – REVISED AUGUST 2011
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POR
Exit From HIBERNATE
Battery Removed
Exit From HIBERNATE
Communication Activity
AND Comm address is for bq27520
bq27520 clears Control Status
[HIBERNATE ] = 0
Recommend Host also set Control
Status [HIBERNATE] = 0
BAT INSERT CHECK
Check for battery insertion
from HALT state.
No gauging
Flags [BAT _DET] = 0
Entry to NORMAL
Flags [BAT _DET] = 1
Exit From NORMAL
Flags [BAT _DET] = 0
NORMAL
Fuel gauging and data
updated every 1s
Exit From SLEEP
Flags [BAT_DET] = 0
HIBERNATE
Disable all bq27520
subcircuits except GPIO.
Negate BAT_GD
Wakeup From HIBERNATE
Communication Activity
AND
Comm address is NOT for bq27520
Entry to SLEEP+
Operation Configuration[SLEEP] = 1
AND
Control Status[SNOOZE] = 1
AND
| AverageCurrent( ) | ≤ Sleep Current
Entry to SLEEP
Operation Configuration[SLEEP] = 1
AND
| AverageCurrent( ) | ≤ Sleep Current
AND
Control Status[SNOOZE] = 0
Exit From WAIT_HIBERNATE
Cell relaxed
AND
| AverageCurrent() | < Hibernate
Current
OR
Cell relaxed
AND
VCELL < Hibernate Voltage
WAIT_HIBERNATE
Fuel gauging and data
updated every 20 seconds
BAT_GD unchanged
System Shutdown
Entry to SLEEP+
Control Status[SNOOZE] = 0
Exit From WAIT _HIBERNATE
Host must set Control Status
[HIBERNATE ] = 0
AND
VCELL > Hibernate Voltage
Exit From SLEEP
| AverageCurrent( ) | > Sleep Current
OR
Exit From SLEEP+ ^{Current is Detected above IWAKE}
Any communication to the gauge
OR
| AverageCurrent( ) | > Sleep Current
OR
Current is Detected above IWAKE
SLEEP+
Fuel gauging and data
updated every 20 seconds
Both LFO and HFO are ON
Entry to SLEEP+
Control Status[SNOOZE] = 1
SLEEP
Fuel gauging and data
updated every 20 seconds
(LFO ON and HFO OFF)
Exit From SLEEP
(Host has set Control Status
[HIBERNATE] = 1
OR
V_CELL < Hibernate Voltage
System Sleep
Figure 5-1. Power Mode Diagram
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 bq27520-G2 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].
5.3.5 Battery Detection Using the BI/TOUT Pin
During power-up or hibernate activities, or any other activity where the bq27520-G2 needs to determine
whether a battery is connected or not, the fuel gauge applies a test for battery presence. First, the
BI/TOUT pin is put into high-Z status. The weak 1.8MΩ pull-up resistor will keep the pin high while no
battery is present. When a battery is inserted (or is already inserted) into the system device, the BI/TOUT
pin will be pulled low. This state is detected by the fuel gauge, which polls this pin every second when the
gauge has power. A battery-disconnected status is assumed when the bq27520-G2 reads a thermistor
voltage that is near 2.5V.
30
FUNCTIONAL DESCRIPTION
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