1 Features

? Standalone charger and easy to configure

? High-efficiency, 1.2MHz, synchronous switch-mode

buck charger

– 92.5 charge efficiency at 2A from 5V input for

1-cell battery

– 91.8 charge efficiency at 2A from 9V input for

1-cell battery

? Single input to support USB input and high voltage

adaptors

– Supports 4.1V - 17V input voltage range with

28V absolute maximum input voltage rating

– Input Voltage Dynamic Power Management

(VINDPM) tracking battery voltage

? High integration

– Integrated reverse blocking and synchronous

switching MOSFET

– Internal input and charge current sense

– Internal loop compensation

– Integrated bootstrap diode

? 3.6V / 4.05V / 4.15V / 4.2V charge voltage

? 3.0A maximum fast charge current

? 200nA low battery leakage current at 4.5V VBAT

? 4.25μA VBUS supply current in IC disable mode

? Charge current thermal regulation at 120°C

? Precharge current: 10 of fast charge current

? Termination current: 10 of fast charge current

? Charge accuracy

– ±0.5 charge voltage regulation

– ±10 charge current regulation

? Safety

– Disable charge for dead battery condition

– Thermal regulation and thermal shutdown

– Input Under-Voltage Lockout (UVLO) and Over-

Voltage Protection (OVP)

– Battery overcharge protection

– Safety timer for precharge and fast charge

– Charge disabled if current setting pin ICHG is

open or short

– Cold/hot battery temperature protection

– Fault report on STAT pin

? Available in a WQFN 3x3-16 package

2 Applications

? Wireless speaker

? Barcode scanner

? Gaming

? Cradle charger

? Cordless power tool

? Building automation

? Medical

3 Description

The BQ25308 is a highly-integrated standalone

switch-mode battery charger for 1-cell Li-ion, Lipolymer,

and LiFePO4 batteries. The BQ25308

supports 4.1V to 17V input voltage and 3A fast charge

current. The integrated current sensing topology of

the device enables high charge efficiency and low

BOM cost. The best-in-class 200nA low quiescent

current of the device conserves battery energy and

maximizes the shelf time for portable devices. The

BQ25308 is available in a 3x3 WQFN package for

easy 2-layer layout and space limited applications.

The BQ25308 supports a 4.1V to 17V input to charge single cell batteries. The BQ25308 provides up to 3A

continuous charge current to a single cell 1S battery. The device features fast charging for portable devices. Its

input voltage regulation delivers maximum charging power to the battery from the input source. The solution is

highly integrated with an input reverse-blocking FET (RBFET, Q1), high-side switching FET (HSFET, Q2), and

low-side switching FET (LSFET, Q3). The device also provides a safety feature that completely inhibits charging

of a dead battery.

The BQ25308 features lossless integrated current sensing to reduce power loss and BOM cost with

minimized component count. It also integrates a bootstrap diode for the high-side gate drive and battery

temperature monitor to simplify system design. The device initiates and completes a charging cycle without

host control. The BQ25308 charge voltage and charge current are set by external resistors. The BQ25308

detects the charge voltage setting at startup and charges the battery in four phases: battery short, preconditioning,

constant current, and constant voltage. At the end of the charging cycle, the charger automatically

terminates if the charge current is below the termination current threshold and the battery voltage is

above the recharge threshold. When the battery voltage falls below the recharge threshold, the charger will

automatically start another charging cycle. The charger provides various safety features for battery charging and

system operations, including battery temperature monitoring based on negative temperature coefficient (NTC)

thermistor, charge safety timer, input over-voltage and over-current protections, as well as battery over-voltage

protection. Pin open and short protection is also built in to protect against the charge current setting pin ICHG

accidently open or short to GND. The thermal regulation regulates charge current to limit die temperature during

high power operation or high ambient temperature conditions.

The STAT pin output reports charging status and fault conditions. When the input voltage is removed, the device

automatically enters HiZ mode with very low leakage current from battery to the charger device. The BQ25308 is

available in a 3mm x 3mm thin WQFN package.