BQ24161B_15 Datasheet, PDF (18/52 Pages) Texas Instruments – bq2416xx 2.5A, Dual-Input, Single-Cell Switched-Mode Li-Ion Battery Charger with Power Path Management and I2C Interface

bq24160, bq24160A, bq24161
bq24161B, bq24163, bq24168
SLUSAO0F – NOVEMBER 2011 – REVISED JULY 2014
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Feature Description (continued)
9.3.6 Battery Only Connected
When a battery with voltage greater than V_BATUVLO is connected with no input source, the battery FET is turned
on similar to supplement mode. In this mode, the current is not regulated; however, there is a short circuit current
limit. If the short circuit limit is reached, the battery FET is turned off for the deglitch time (t_DGL(SC1)). After the
recovery time (t_REC(SC1)), the battery FET is turned on to test and see if the short has been removed. If it has not,
the FET turns off and the process repeats until the short is removed. This process is to protect the internal FET
from over current. If an external FET is used for discharge, the external FET's body diode prevents the load on
SYS from being disconnected from the battery. If the battery voltage is less than V_BATUVLO, the internal battery
FET (Q4) remains off and BAT is high-impedance. This prevents further discharging of deeply-discharged
batteries.
9.3.7 Battery Discharge FET (BGATE)
The bq2416xx contains a MOSFET driver to drive the gate of an external discharge FET between the battery and
the system output. This external FET provides a low impedance path when supplying the system from the
battery. Connect BGATE to the gate of the external discharge MOSFET. BGATE is on under the following
conditions:
1. No input supply connected.
2. HZ_MODE bit = 1
3. CD pin = 1
9.3.8 DEFAULT Mode
DEFAULT mode is used when I²C communication is not available. DEFAULT mode is entered in the following
situations:
1. When the charger is enabled and V_BAT< V_BATGD before I²C communication is established
2. When the watchdog timer expires without a reset from the I²C interface and the safety timer has not expired.
3. When the device comes out of any fault condition (sleep mode, OVP, faulty adapter mode, etc.) before I²C
communication is established
In DEFAULT mode, the I²C registers are reset to the default values. The 27-minute safety timer (no timer for
bq24168) is reset and starts when DEFAULT mode is entered. The default value for VBATREG is 3.6V, and the
default value for I_CHARGE is 1A. The input current limit for the IN input is set to 1.5A. The input current limit for the
USB input is determined by the D+/D– detection (bq24160/3) or PSEL (bq24161/1B/8). PSEL and D+/D–
detection have no effect on the IN input. Default mode is exited by programming the I²C interface. Once I²C
communication is established, PSEL has no effect on the USB input. Note that if termination is enabled and
charging has terminated, a new charge cycle is NOT initiated when entering DEFAULT mode.
9.3.9 Safety Timer and Watchdog Timer (bq24160/ bq24161/ bq24161B/ bq24163 only)
At the beginning of charging process, the bq24160/1/1B/3 starts the safety timer. This timer is active during the
entire charging process. If charging has not terminated before the safety timer expires, charging is disabled, the
charge parameters are reset to the default values and the CE bit is written to a “1”. The length of the safety timer
is selectable using the I²C interface. A single 128μs pulse is sent on the STAT and INT outputs and the STATx
bits of the status registers are updated in the I²C. In DEFAULT mode, the safety timer can be reset and a new
charge cycle initiated by input supply power on reset, removing/inserting battery or toggling the CD pin. In HOST
mode, the CE bit is set to a '1' when the safety timer expires. The CE bit must be cleared to a '0' in order to
resume charging and clear the safety timer fault. The safety timer duration is selectable using the TMR_X bits in
the Safety Timer Register/ NTC Monitor register. Changing the safety timer duration resets the safety timer. This
function prevents continuous charging of a defective battery. During the fast charge (CC) phase, several events
increase the timer duration by 2X if the EN_2X_TMR bit is set in the register.
1. The system load current reduces the available charging current.
2. The input current needed for the fast charge current is limited by the input current loop.
3. The input current is reduced because the VINDPM loop is preventing the supply from crashing.
4. The device has entered thermal regulation because the IC junction temperature has exceeded TJ(REG).
5. The LOW_CHG bit is set.
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