Datasheet

bq27541-G1
www.ti.com SLUSAL6C –NOVEMBER 2011–REVISED OCTOBER 2012
The [BATLOW] of Flags() is set high to indicate Voltage() is below the BL Set Volt Threshold for predefined
duration set in the BL Volt Time. This flag returns to low once battery voltage is above or equal the BL Clear
Volt threshold. It is recommended that the BL Set Volt Threshold is configured lower than the BL Clear Volt
threshold to provide proper voltage hysteresis.
The [BATHI] and [BATLOW] flags can be configured to control the interrupt pin (SE or HDQ) by enabling
interrupt mode. Refer to “Interrupt Mode” section for details.
Internal Short Detection
The bq27541-G1 can indicate detection of an internal battery short by setting the [SE_ISD] bit in Pack
Configuraton B. The device compares the self-discharge current calculated based StateOfCharge() in relaxation
mode and AverageCurrent() measured in the system. The self-discharge rate is measured at 1 hour interval.
When battery SelfDischargeCurrent() is less than the predefined (-Design Capacity / ISD Current threshold),
the [ISD] of Flags() is set high. The [ISD] of Flags() can be configured to control interrupt pin (SE or HDQ) by
enabling interrupt mode. Refer to “Interrupt Mode” section for details.
Tab Disconnection Detection
The bq27541-G1 can indicate tab disconnection by detecting change of StateOfHealth(). This feature is enabled
by setting [SE_TDD] bit in Pack Configuraton B. The [TDD] of Flags() is set when the ratio of current
StateOfHealth() divided by the previous StateOfHealth() reported is less than TDD SOH Percent. The [TDD] of
Flags() can be configured to control an interrupt pin (SE or HDQ) by enabling interrupt mode. Refer to “Interrupt
Mode” section for details.
TEMPERATURE MEASUREMENT AND THE TS INPUT
The bq27541-G1 measures battery temperature via the TS input in order to supply battery temperature status
information to the fuel gauging algorithm and charger-control sections of the gauge. Alternatively, the gauge can
also measure internal temperature via its on-chip temperature sensor, but only if the [TEMPS] bit of Pack
Configuration register is cleared.
Regardless of which sensor is used for measurement, a system processor can request the current battery
temperature by calling the Temperature( ) function (see Section Standard Data Commands, for specific
information).
The thermistor circuit requires the use of an external 10kΩ thermistor with negative temperature coefficient (NTC)
thermistor with R25 = 10kΩ ± 1% and B25/85 = 3435kΩ ± 1% (such as Semitec 103AT) that connects between
the Vcc and TS pins. Additional circuit information for connecting the thermistor to the bq27541 is shown in the
Reference Schematic.
OVER-TEMPERATURE INDICATION
Over-Temperature: Charge
If during charging, Temperature( ) reaches the threshold of OT Chg for a period of OT Chg Time and
AverageCurrent( ) ≥ Chg Current Threshold, then the [OTC] bit of Flags( ) is set. When Temperature( ) falls to
OT Chg Recovery, the [OTC] of Flags( ) is reset.
If OT Chg Time = 0, the feature is disabled.
Over-Temperature: Discharge
If during discharging, Temperature( ) reaches the threshold of OT Dsg for a period of OT Dsg Time, and
AverageCurrent( ) ≤ -Dsg Current Threshold, then the [OTD] bit of Flags( ) is set. When Temperature( ) falls to
OT Dsg Recovery, the [OTD] bit of Flags( ) is reset.
If OT Dsg Time = 0, the feature is disabled.
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