Introducing Richtek Switching Chargers -
Key functions, applications and product portfolio
Anyone owning a smartphone will agree that longer battery life and shorter charging times are key features for portable devices. But do you know what technology is behind the powerful charging systems in today’s smartphones, and what are the limiting factors in the quest for ever faster charging? In order to quickly charge large capacity batteries in portable devices with power-hungry processors inside, more powerful chargers are needed. High current switching chargers in combination with smart adapters and intelligent control systems make it possible to set the optimal charge conditions to quickly and safely charge Li-Ion batteries in a wide range of portable devices. This feature story explains several application aspects of switching chargers for single cell Li-Ion batteries and introduces three switching chargers from the Richtek Li-Ion charger portfolio: RT9458 (1.55A), RT9460 (3A) and RT9466 (5A).
A typical Li-Ion charge cycle consists of a constant current (CC) regulation mode and a constant voltage (CV) regulation mode. Most energy is transferred during the CC mode, so higher CC current will reduce charge time. Standard Li-Ion batteries can be charged with 0.5C ~ 1C charge currents, where C is the capacity of the battery. Some batteries can be charged with higher currents, depending on construction, internal impedance and temperature. Read More
Challenges in fast charging:
  • Most single Li-Ion cell powered devices are charged using the USB port which can limit the maximum current.
  • High charge currents lead to errors in battery voltage sense due to resistance in the charge path.
  • Maximum allowable temperature of the charger IC and battery will limit the fast charging current.
  • System load during charging will consume some energy available for battery charging.
  • Read More
Switching charger ICs need special functions to deal with input compatibility issues and optimize battery charging:
  • Smart USB port detection can determine the maximum available input current.
  • Average Input Current Regulation (AICR) adjusts charge current to the max available input current.
  • Minimum Input Voltage Regulation (MIVR) avoids overloading the power source.
  • IR compensation function avoids voltage sense errors and extends the CC charge mode. Click here for an example without and with IR compensation.
  • Battery & Charger IC thermal sense adjusts charging parameters at different temperatures to ensure safe charging conditions.
  • Automatic power path function selects system power source and balances power distribution. Chick here to see diagrams of Buck converter charging paths in different charging scenarios.
  • USB on the go (OTG) Boost control transforms the charging input into a 5V power output. Programmable OTG current limit allows setting the USB port output capability.
  • Charging with higher input voltage i.e. 9V or 12V reduces input current and allows higher power transfer. Read more to learn how this works. Read More
Introducing three Richtek switching chargers:
RT9458 is a basic switching charger: It can replace linear chargers to achieve shorter charge time and better efficiency. It is suitable for Li-Ion cells up to 1800mAh.
RT9460 is a more advanced switching charger with wide range input, USB port detection, power path, NTC sence, suitable for Li-Ion cells from 2500~2800mAh.
RT9466 is a very powerfull 5A swiching charger with a wide range of features for high current charging, supporting MTK Pump Express 1.0 and 2.0 for dynamic input voltage control, to be used with high capacity cells up to 4000mAh.
Coming soon: RT9468 supports Programmable Power Supply (PPS) capability, which allows optimized switching charger mode or bypassed charging directly from adapter to battery using the USB-PD 3.0 communication protocol.
See more product details on charging parameters, OTG Boost parameters and protection functions. Read More
➔ Get your switching charger design started in no time!
Read the full application note "Switching Battery Chargers"
New Products
RT9481 is a powerful and easy to use Power Bank Solution (EZPBS®) in WQFN-24L 4x4 package. RT9481 is a highly integrated single chip solution with I2C interface including a 2.7A switching charger with 3A boost output function, programmable USBOUT Load Switch, BC1.2 Adapter Detection, DCP controller and a LDO.
⇒ Also see RT9481 Evaluation Board
RT9081A is a 500mA, Bias Rail LDO with Ultra Low Dropout (140mV@500mA) in a small DFN-6L 1.2x1.2mm package. Operates from 0.8V-5.5V input and 2.4V-5.5V bias rail. Stable with 1µF Cout, RT9081A regulates both fixed (0.9V-1.8V) & Adj. (0.8V-3.6V) Vout at 1.5 % accuracy. The low dropout and good high frequency PSRR makes this LDO very suitable to derive low voltages supplies like 1.0V or 1.2V from a low 1.5V voltage intermediate buck rail and a 3.3V or 5V bias rail. Highly suitable for industrial applications like Telecom, Enterprise, Server, Medical, etc.