BQ27520-G2 Datasheet, PDF (33/47 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated LDO

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bq27520-G2
SLUSAB7A – MARCH 2011 – REVISED AUGUST 2011
When PFC = 1, the bq27520-G2 can indicate when battery temperature has fallen below or risen above
predefined thresholds Suspend Low Temp or Suspend High Temp, respectively. In this mode, the
[XCHG] bit is set to indicate this condition. The [XCHG] bit is cleared once the battery temperature returns
to the range [Charge Inhibit Temp Low + Temp Hys, Charge Inhibit Temp High – Temp Hys].
The charging should not start when the temperature is below the Charge Inhibit Temp Low or above the
Charge Inhibit Temp High. The charging can continue if the charging starts inside the window [Charge
Inhibit Temp Low, Charge Inhibit Temp High] until the temperature is either below Suspend Low Temp or
above the Suspend Low Temp. Therefore, the window [Charge Inhibit Temp Low, Charge Inhibit Temp
High] must be inside the window of [Suspend Low Temp, Suspend High Temp].
5.7 POWER MODES
The bq27520-G2 has different power modes: BAT INSERT CHECK, NORMAL, SLEEP+, SLEEP and
HIBERNATE. In NORMAL mode, the bq27520-G2 is fully powered and can execute any allowable task. In
SLEEP+ mode, both low frequency and high frequency oscillators are active. Although the SLEEP+ has
higher current consumption than the SLEEP mode, it is also a reduced power mode. In SLEEP mode, the
fuel gauge turns off the high frequency oscillator and exists in a reduced-power state, periodically taking
measurements and performing calculations. In HIBERNATE mode, the fuel gauge is in a low power state,
but can be woken up by communication or certain I/O activity. Finally, the BAT INSERT CHECK mode is a
powered-up, but low-power halted, state, where the bq27520-G2 resides when no battery is inserted into
the system.
The relationship between these modes is shown in Figure 5-1.
5.7.1 BAT INSERT CHECK Mode
This mode is a halted-CPU state that occurs when an adapter, or other power source, is present to power
the bq27520-G2 (and system), yet no battery has been detected. Depending on the setting of the [BIE] bit
in the Operation Configuration B dataflash register, the bq27520-G2 will detect battery insertion either
through use of the thermistor network and BI/TOUT pin, or the host can use the BAT_INSERT and
BAT_REMOVE commands to inform the battery presence status. When battery insertion is detected, a
series of initialization activities begin, which include: OCV measurement, setting the BAT_GD pin, and
selecting the appropriate battery profiles.
Some commands, issued by a system processor, can be processed while the bq27520-G2 is halted in this
mode. The gauge will wake up to process the command, then return to the halted state awaiting battery
insertion.
5.7.2 NORMAL MODE
The fuel gauge is in NORMAL mode when not in any other power mode. During this mode,
AverageCurrent( ), Voltage( ) and Temperature( ) measurements are taken, and the interface data set is
updated. Decisions to change states are also made. This mode is exited by activating a different power
mode.
Because the gauge consumes the most power in NORMAL mode, the Impedance Track™ algorithm
minimizes the time the fuel gauge remains in this mode.
5.7.3 SLEEP MODE
SLEEP mode is entered automatically if the feature is enabled (Operation Configuration [SLEEP] = 1)
and AverageCurrent( ) is below the programmable level Sleep Current. Once entry into SLEEP mode has
been qualified, but prior to entering it, the bq27520-G2 performs an coulomb counter autocalibration to
minimize offset.
During SLEEP mode, the bq27520-G2 periodically takes data measurements and updates its data set.
However, a majority of its time is spent in an idle condition.
Copyright © 2011, Texas Instruments Incorporated
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FUNCTIONAL DESCRIPTION
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