BQ24085_17 Datasheet, PDF (22/42 Pages) Texas Instruments – 750-mA Single-Chip Li-Ion and Li-Pol Charge Management IC With Thermal Regulation

bq24085, bq24086, bq24087, bq24088
SLUS784E – DECEMBER 2007 – REVISED DECEMBER 2015
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See the Application and Implementation section for additional details on start-up operation with V_(BAT) < V_(SC).
8.3.16 Startup With Deeply Depleted Battery Connected
The bq24085/6/7/8 charger furnishes the programmed charge current if a battery is detected. If no battery is
connected the bq24085/6/7/8 operates as follows:
• The output current is limited to 15 mA (typical), if the voltage at BAT pin is below the short circuit detection
threshold V_(SC), 1.8 V typical.
• The output current is regulated to the programmed pre-charge current if V_(SC) < V_(BAT) < V_(LOWV).
• The output current is regulated to the programmed fast charge current If V_(BAT) > V_(LOWV) AND voltage
regulation is not reached.
The output voltage collapses if no battery is present and the end equipment requires a bias current larger than
the available charge current.
8.4 Device Functional Modes
8.4.1 Power Down
The bq24085/6/7/8 family is in a power-down mode when the input power voltage (IN) is below the power-down
threshold V_(PDWN). During the power-down mode all IC functions are off, and the host commands at the control
pins are not interpreted. The integrated power MOSFET connected between IN and OUT pins is off, the status
output pins STAT1 and STAT2 are set to high impedance mode and PG output is set to the high impedance
state.
8.4.2 Sleep Mode
The bq24085/6/7/8 enters the sleep mode when the input power voltage (IN) is above the power-down threshold
V(PDWN) but still lower than the input power detection threshold, V(IN) < V(OUT) + V_IN(DT).
During the sleep mode the charger is off, and the host commands at the control pins are not interpreted. The
integrated power mosfet connected between IN and OUT pins is off, the status output pins STAT1 and STAT2
are set to the high impedance state and the PG output indicates input power not detected.
The sleep mode is entered from any other state, if the input power (IN) is not detected.
8.4.3 Overvoltage Lockout
The input power is detected when the input voltage V(IN) > V(OUT) + V_IN(DT). When the input power is detected
the bq24085/6/7/8 transitions from the sleep mode to the power-on-reset mode. In this mode of operation, an
internal timer T_(POR) is started and internal blocks are reset (power-on-reset). Until the timer expires, the STAT1
and STAT2 outputs indicate charger OFF, and the PG output indicates the input power status as not detected.
At the end of the power-on-reset delay, the internal comparators are enabled, and the STAT1, STAT2 and PG
pins are active.
8.4.4 Stand-By Mode
In the bq24085/6/7/8, the stand-by mode is started at the end of the power-on-reset phase, if the input power is
detected and CE = HI. In the stand-by mode, selected blocks in the IC are operational, and the control logic
monitors system status and the control pins to define if the charger will be set to ON or OFF mode. The
quiescent current required in stand-by mode is 100 μA typical.
If the CE pin is not available, the bq24085/6/7/8 enters the begin charge mode at the end of the power-on-reset
phase.
8.4.5 Begin Charge Mode
All blocks in the IC are powered up, and the bq24085/6/7/8 is ready to start charging the battery pack. A new
charge cycle is started when the control logic decides that all conditions required to enable a new charge cycle
are met. During the begin charge phase all timers are reset, then the IC enters the charging mode.
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