BQ24196_17 Datasheet, PDF (20/50 Pages) Texas Instruments – I2C Controlled 2.5-A Single Cell USB/Adapter Charger with Narrow VDC Power Path Management and USB OTG

bq24196
SLUSB98A – OCTOBER 2012 – REVISED DECEMBER 2014
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8.3.3.4 Charging Termination
The bq24196 terminates a charge cycle when the battery voltage is above recharge threshold, and the current is
below termination current. After the charging cycle is complete, the BATFET turns off. The converter keeps
running to power the system, and BATFET can turn back on to engage supplement mode.
When termination occurs, the status register REG08[5:4] is 11, and an INT is asserted to the host. Termination is
temporarily disabled if the charger device is in input current/voltage regulation or thermal regulation. Termination
can be disabled by writing 0 to REG05[7].
8.3.3.4.1 Termination when REG02[0] = 1
When REG02[0] is HIGH to reduce the charging current by 80%, the charging current could be less than the
termination current. The charger device termination function should be disabled. When the battery is charged to
fully capacity, the host disables charging through CE pin or REG01[5:4].
8.3.3.4.2 Termination when REG05[6] = 1
Usually the STAT bit indicates charging complete when the charging current falls below termination threshold.
Write REG05[6] = 1 to enable an early “charge done” indication on STAT pin. The STAT pin goes high when the
charge current reduces below 800 mA. The charging cycle is still on-going until the current falls below the
termination threshold.
8.3.3.5 Charging Safety Timer
The bq24196 has safety timer to prevent extended charging cycle due to abnormal battery conditions.
In default mode, the device keeps charging the battery with 5-hour fast charging safety timer regardless of
REG05[2:1] default value. At the end of the 5 hours, the EN_HIZ (REG00[7]) is set to signal the buck converter
stops and the system load is supplied by the battery. The EN_HIZ bit can be cleared to restart the buck
converter.
In host mode, the device keeps charging the battery until the fast charging safety timer expired. The duration of
safety timer can be set by the REG05[2:1] bits (default = 8 hours). At the end of safety timer, the EN_HIZ
(REG00[7]) is cleared to signal the buck converter continues to operation to supply system load.
The safety timer is 1 hour when the battery is below BATLOWV threshold. The user can program fast charge
safety timer through I²C (REG05[2:1]). When safety timer expires, the fault register REG09[5:4] goes 11 and an
INT is asserted to the host. The safety timer feature can be disabled via I2C (REG05[3]).
The following actions restart the safety timer:
• At the beginning of a new charging cycle
• Toggle the CE pin HIGH to LOW to HIGH (charge enable)
• Write REG01[5:4] from 00 to 01 (charge enable)
• Write REG05[3] from 0 to 1 (safety timer enable)
During input voltage/current regulation or thermal regulation, or when FORCE_20PCT (REG02[0]) bit is set, the
safety timer counts at half clock rate since the actual charge current is likely to be below the register setting. For
example, if the charger is in input current regulation (IINDPM) throughout the whole charging cycle, and the
safety time is set to 5 hours, the safety timer will expire in 10 hours. This feature can be disabled by writing 0 to
REG07[6].
It is recommended to disable safety timer first by clearing REG05[3] bit before safety timer configuration is
changed. The safety timer should be re-enabled by setting REG05[3] bit.
8.3.3.6 USB Timer when Charging from USB100mA Source
The total charging time in default mode from USB100-mA source is limited by a 45-min max timer. At the end of
the timer, the device stops the converter and goes to HIZ.
8.3.4 Status Outputs (PG, STAT, and INT)
8.3.4.1 Power Good Indicator (PG)
In bq24196, PG goes LOW to indicate a good input source when:
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