BQ25895_16 Datasheet, PDF (25/67 Pages) Texas Instruments – Adjustable Voltage 3.1-A Boost Operation

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bq25895
SLUSC88A – MARCH 2015 – REVISED MAY 2016
8.2.7.5.2 Cold/Hot Temperature Window in Boost Mode
For battery protection during boost mode, the device monitors the battery temperature to be within the V_BCOLDx to
V_BHOTx thresholds unless boost mode temperature is disabled by setting BHOT bits to 11. When temperature is
outside of the temperature thresholds, the boost mode and BATFET are disabled and BATFET_DIS bit is set to
reduce leakage current on PMID. Once temperature returns within thresholds, the host can clear BATFET_DIS
bit or provide logic low to high transition on QON pin to enable BATFET and boost mode.
VREF
Temperature Range to
Boost
V _BCOLDx
( -10ºC / 20ºC)
Boost Disable
Boost Enable
V _BHOTx
(55ºC / 60ºC / 65ºC)
Boost Disable
AGND
Figure 16. TS Pin Thermistor Sense Thresholds in Boost Mode
8.2.7.6 Charging Safety Timer
The device has built-in safety timer to prevent extended charging cycle due to abnormal battery conditions. The
safety timer is 4 hours when the battery is below V_BATLOWV threshold. The user can program fast charge safety
timer through I²C (CHG_TIMER bits). When safety timer expires, the fault register CHRG_FAULT bits are set to
11 and an INT is asserted to the host. The safety timer feature can be disabled via I2C by setting EN_TIMER bit.
During input voltage, current or thermal regulation, the safety timer counts at half clock rate as the actual charge
current is likely to be below the register setting. For example, if the charger is in input current regulation
(IDPM_STAT = 1) throughout the whole charging cycle, and the safety time is set to 5 hours, the safety timer will
expire in 10 hours. This half clock rate feature can be disabled by writing 0 to TMR2X_EN bit.
8.2.8 Battery Monitor
The device includes a battery monitor to provide measurements of VBUS voltage, battery voltage, system
voltage, thermistor ratio, and charging current, and charging current based on the device’s modes of operation.
The measurements are reported in Battery Monitor Registers (REG0E-REG12). The battery monitor can be
configured as two conversion modes by using CONV_RATE bit: one-shot conversion (default) and 1 second
continuous conversion.
For one-shot conversion (CONV_RATE = 0), the CONV_START bit can be set to start the conversion. During the
conversion, the CONV_START is set and it is cleared by the device when conversion is completed. The
conversion result is ready after t_CONV (maximum 1 second).
For continuous conversion (CONV_RATE = 1), the CONV_RATE bit can be set to initiate the conversion. During
active conversion, the CONV_START is set to indicate conversion is in progress. The battery monitor provides
conversion result every 1 second automatically. The battery monitor exits continuous conversion mode when
CONV_RATE is cleared.
When battery monitor is active, the REGN power is enabled and can increase device quiescent current.
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