BQ24262_15 Datasheet, PDF (22/56 Pages) Texas Instruments – bq2426x 3-A, 30-V, Host-Controlled Single-Input, Single-Cell Switched-Mode Li-Ion Battery Charger With Power-Path Management and USB-OTG Support

Not Recommended for New Designs : bq24260, bq24261
bq24260, bq24261, bq24261M, bq24262
SLUSBU4D – DECEMBER 2013 – REVISED APRIL 2015
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Device Functional Modes (continued)
9.4.13 Power Source Selector Input (PSEL, bq24261/2 only)
The bq24261/2 contains a PSEL input that is used to program the input current limit during DEFAULT mode.
Drive PSEL high to indicate a USB source is connected to the input and program the 100 mA (bq24261/1M) or
500mA (bq24262) current limit for IN. Drive PSEL low to indicate that an AC Adapter is connected to the input.
When PSEL is low, the IC starts up with a 1.5-A input current limit. Once an I²C write is done and the device is in
HOST mode, the PSEL has no effect on the input current limit until the watchdog timer expires and returns
thebq24260/1/1M/2 to DEFAULT mode.
9.4.14 Safety Timer and Watchdog Timer in Charge Mode (bq24260/1/1M only)
At the beginning of charging process, the bq24260/1/1M starts the safety timer. This timer is active during the
entire charging process. If charging has not terminated before the safety timer expires, the IC enters suspend
mode where charging is disabled. When a safety timer fault occurs, a single 128μs pulse is sent on the STAT
and INT outputs and the STATx and FAULT_x bits of the status registers are updated in the I²C. The CE bit, Hi-Z
mode, or power must be toggled in order to clear the safety timer fault. The safety timer duration is selectable
using the TMR_X bits in the Safety Timer Register/ NTC Monitor register. When the safety timer is active,
changing the safety timer duration resets the safety timer. The bq24260/1/1M also contains a 2X_TIMER bit that
enables the 2x timer function to prevent premature safety timer expiration when the charge current is reduced by
a load on SYS or a NTC condition. When 2X_TIMER is enabled, the timer runs at half speed when any loop is
active other than CC or CV. This includes V_INDPM, input current limit, or thermal regulation. The timer also runs at
half speed during TS warm/cool conditions and when the LOW_CHG bit is set to 1.
In addition to the safety timer, the bq24260/1/1M contains a 30-second (t_WATCHDOG) watchdog timer that monitors
the host through the I²C interface. Once a write is performed on the I²C interface, a watchdog timer is started.
The watchdog timer is reset by the host using the I²C interface. This is done by writing a 1 to the reset bit
(TMR_RST) in the control register. The TMR_RST bit is automatically set to 0 when the watchdog timer is reset.
This process must continue as long as the input is connected in order to maintain the register contents. If the
watchdog timer expires, the IC enters DEFAULT mode where the default register values are loaded, the safety
timer restarts at 2 minutes once charging continues. The I²C may be accessed again to reinitialize the desired
values and restart the watchdog timer. The watchdog timer flow chart is shown in Figure 12.
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