Datasheet

PRE-CHARGE
CURRENT AND
TERMINATION
THRESHOLD
FAST-CHARGE
CURRENT
T
(PRECHG)
Charge
Complete
Status,
Charger
Off
Pre-
Conditioning
Phase
Current
Regulation
Phase
VoltageRegulationand
ChargeTermination
Phase
Battery
Voltage,
V
(OUT)
BatteryCurrent,
I
(OUT)
DONE
0A
Thermal
Regulation
Phase
Temperature, Tj
I
O(OUT)
T
(THREG)
I
(TERM)
I
O(PRECHG)
V
O(REG)
V
O(LOWV)
DONE
T
(CHG)
bq24050
bq24052
bq24055
SLUS940B –SEPTEMBER 2009–REVISED JUNE 2012 www.ti.com
Figure 23. Charging Profile with Thermal Regulation
DETAILED FUNCTIONAL DESCRIPTION
Power-Down, or Undervoltage Lockout (UVLO):
The bq2405x family is in power down mode if the IN pin voltage is less than UVLO. The part is considered
“dead” and all the pins are high impedance. Once the IN voltage rises above the UVLO threshold the IC will
enter Sleep Mode or Active mode depending on the OUT pin (battery) voltage.
Power-up
The IC is alive after the IN voltage ramps above UVLO (see sleep mode), resets all logic and timers, and starts
to perform the D+D– detection along with many of the continuous monitoring routines. The D+/D– detection
typically take less than 100ms, but can take as long as 600ms if there is no activity on the D+ or D– lines which
indicates the device transceiver nor an adaptor is present. Typically the input voltage quickly rises through the
UVLO and sleep states where the IC declares power good, starts the qualification charge at 100mA, finishes the
USB detection routine, sets the input current limit threshold base on the source detected (ISET=adaptor or
100mA=USB), starts the safety timer and enables the CHG pin. See Figure 25
D+, D– Detection:
This detection is designed to give the charger advance notice that an adaptor or USB port is connect for the
cases where the battery is discharged and device transceiver is not able to communicate with a USB host or
there is not a device transceiver. If an adaptor is detected, then the charger can immediately start charging at the
programmed ISET level. Without this early detection, the charger would have to default to the 100mA input
current level to make sure it was not over-loading a low power USB port. The detection method monitors the D+,
D– communication lines looking for a short between the lines (Adaptor source connected) or pull down resistors
on D+, D– (USB source connected) to determine what source is connected (no USB communication takes
place). If an adaptor source is detected then the charger will transition from the 100mA startup level to the ISET
programmed current level. If a USB port is detected, the input current limit will stay at the 100mA level. If a
different charge level is desired, than the one detected, the host has to change the state of the ISET2 pin
(signals the internal logic to start using the ISET2 as the program pin) and then set to the desired state.
16 Copyright © 2009–2012, Texas Instruments Incorporated