The bq25898, bq25898D are highly-integrated 4-A switch-mode
battery charge management and system power path management devices for single cell Li-Ion and
Li-polymer battery. The devices support high input voltage fast charging.
The low impedance power path optimizes switch-mode operation efficiency, reduces battery
charging time and extends battery life during discharging phase. The I2C
Serial interface with charging and system settings makes the device a truly flexible
The bq25898/98D is a highly-integrated 4-A switch-mode battery charge management and
system power path management device for single cell Li-Ion and Li-polymer battery. It features fast
charging with high input voltage support for a wide range of smartphone, tablet and portable
devices. Its low impedance power path optimizes switch-mode operation efficiency, reduces battery
charging time and extends battery life during discharging phase. It also integrates Input Current
Optimizer (ICO) and Resistance Compensation (IRCOMP) to deliver maximum charging power to battery.
The solution is highly integrated with input reverse-blocking FET (RBFET, Q1), high-side switching
FET (HSFET, Q2), low-side switching FET (LSFET, Q3), and battery FET (BATFET, Q4) between system
and battery. It also integrates the bootstrap diode for the high-side gate drive and battery
monitor for simplified system design. The I2C serial interface with
charging and system settings makes the device a truly flexible solution.
The device supports a wide range of input sources, including standard USB host port, USB
charging port, and USB compliant adjustable high voltage adapter. To support fast charging using
adjustable high voltage adapter, the bq25898D provides support for
MaxCharge™ handshake using D+/D- pins and DSEL pin
for USB switch control. In addition, both bq25898D and bq25898 include interface to support
adjustable high voltage adapter using input current pulse protocol. To set the default input
current limit, device uses the built-in USB interface (bq25898D) or takes the result from detection
circuit in the system (bq25898), such as USB PHY device. The device is compliant with USB 2.0 and
USB 3.0 power spec with input current and voltage regulation. In addition, the Input Current
Optimizer (ICO) supports the detection of maximum power point detection of the input source without
overload. The device also meets USB On-the-Go (OTG) operation power rating specification by
supplying 5 V (Adjustable 4.5V-5.5V) on VBUS with current limit up to 2.4 A.
The power path management regulates the system slightly above battery voltage but does
not drop below 3.5V minimum system voltage (programmable). With this feature, the system maintains
operation even when the battery is completely depleted or removed. When the input current limit or
voltage limit is reached, the power path management automatically reduces the charge current to
zero. As the system load continues to increase, the power path discharges the battery until the
system power requirement is met. This operation prevents overloading the input source.
The device initiates and completes a charging cycle without software control. It
automatically detects the battery voltage and charges the battery in three phases:
pre-conditioning, constant current and constant voltage. At the end of the charging cycle, the
charger automatically terminates when the charge current is below a preset limit in the constant
voltage phase. When the full battery 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 negative thermistor monitoring, charging safety timer and
overvoltage/overcurrent protections. The thermal regulation reduces charge current when the
junction temperature exceeds 120°C (programmable). The STAT output reports the charging status and
any fault conditions. The PG output (bq25898) indicates if a good power
source is present. The INT immediately notifies host when fault occurs.
The device also provides a 7-bit analog-to-digital converter (ADC) for monitoring charge
current and input/battery/system (VBUS, BAT, SYS, TS) voltages. The QON pin provides BATFET
enable/reset control to exit low power ship mode or full system reset function.
The devices are available in a 42-ball, 2.8 mm x 2.5 mm DSBGA package.
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