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BQ24292I Datasheet, PDF (27/42 Pages) Texas Instruments – I2C Controlled 4.5A Single Cell USB/Adapter Charger With Narrow VDC Power Path Management and USB OTG
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bq24292i
SLUSBI4 – APRIL 2013
Charging Termination
The device 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].
Termination when FORCE_20PCT (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 can disable charging through CE pin or REG01[5:4].
Termination when TERM_STAT (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 800mA. The charging cycle is still on-going until the current falls below the
termination threshold.
Charging Safety Timer
The device has safety timer to prevent extended charging cycle due to abnormal battery conditions. The safety
timer is 2 hours 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:
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, 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 configuraiton is
changed. The safety timer can be re-enabled by setting REG05[3] bit.
USB Timer when Charging from USB100mA Source
The total charging time in default mode from USB100mA source is limited by a 45-min max timer. At the end of
the timer, the device stops the converter and goes to HIZ.
Host Mode and Default Mode
The device is a host controlled device, but it can operate in default mode without host management. In default
mode, device can be used as an autonomous charger with no host or with host in sleep.
When the charger is in default mode, REG09[7] is HIGH. When the charger is in host mode, REG09[7] is LOW.
After power-on-reset, the device starts in watchdog timer expiration state, or default mode. All the registers are in
the default settings.
Any write command to the device transitions the device from default mode to host mode. All the device
parameters can be programmed by the host. To keep the device in host mode, the host has to reset the
watchdog timer by writing 1 to REG01[6] before the watchdog timer expires (REG05[5:4]), or disable watchdog
timer by setting REG05[5:4]=00.
Copyright © 2013, Texas Instruments Incorporated
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