1 Features
• Charging
– 1% Charge voltage accuracy
– 10% Charge current accuracy
– Pin selectable USB 100 mA and 500 mA
maximum input current limit
– Programmable termination and precharge
threshold, BQ24040 and BQ24045
– High voltage (4.35 V) chemistry support with
BQ24045
• Protection
– 30V Input rating; with 6.6 V or 7.1 V input
overvoltage protection
– Input voltage dynamic power management
– 125°C thermal regulation; 150°C thermal
shutdown protection
– OUT Short-circuit protection and ISET short
detection
– Operation over JEITA range via battery NTC –
1/2 fast-charge-current at Cold, 4.06V at Hot,
BQ24040 and BQ24045
– Fixed 10 hour safety timer, BQ24040 and
BQ24045
• System
– Automatic termination and timer disable mode
(TTDM) for absent battery pack with thermistor,
BQ24040 and BQ24045
– Status indication – charging and done
– Available in small 2 × 2 mm2 DFN-10 package
– Integrated auto start function for production line
testing, BQ24041
• Functional Safety-Capable (BQ24040)
– Documentation available to aid functional safety
system design
• Safety-Related Certifications:
– IEC 62368-1 CB Certification (BQ24040,
BQ24045)

2 Applications
• TWS Headsets and headphones
• Smartwatches and wristbands
• Wireless speakers
• Mobile POS
• Portable medical devices

3 Description
The BQ2404x series of devices are highly integrated
Li-Ion and Li-Pol linear chargers devices targeted at
space-limited portable applications. The devices
operate from either a USB port or AC adapter. The
high input voltage range with input overvoltage
protection supports low-cost unregulated adapters.
The BQ2404x has a single power output that charges
the battery. A system load can be placed in parallel
with the battery as long as the average system load
does not keep the battery from charging fully during
the 10 hour safety timer.
The battery is charged in three phases: conditioning,
constant current and constant voltage. In all charge
phases, an internal control loop monitors the IC
junction temperature and reduces the charge current
if an internal temperature threshold is exceeded.
The charger power stage and charge current sense
functions are fully integrated. The charger function
has high accuracy current and voltage regulation
loops, charge status display, and charge termination.
The pre-charge current and termination current
threshold are programmed through an external
resistor on the BQ24040 and BQ24045. The fast
charge current value is also programmable through an
external resistor.