Wearable devices are small, thin and light-weight, often powered by lithium-ion coin cell batteries. As more functionality is added to wearable devices, extending battery life becomes a key factor for power management design. Richtek has been developing a new range of power solutions specifically targeted for wearable designs, like AMOLED display drivers, ultra low Iq DC/DC converters, battery chargers designed for low capacity Li-Ion batteries, wireless power receivers with embedded charger, and tiny fuel gauge ICs.

Many wearable solutions use AMOLED displays due to their low power consumption and high contrast ratio display. AMOLED panel drive is extremely sensitive to noise, and requires special designed power ICs to provide very precise and noise free voltages.

RT4723 is a dual output AMOLED Power IC with integrated boost converter for Vpos and a charge pump for Vneg in small CSP-15B 1.39x2.07 package, specifically designed for 1’’ to 2’’ panels in battery-powered wearable/portable applications. The total solution has better light load efficiency compared to competitor solutions and features an extremely small PCB footprint.

Wearable applications that contain MCUs for computing require lower voltage rails for the core supply, like 0.7V to 1.2V. The load on these rails will be idle for most of the time with a sudden higher current during data processing, storage or transmission. This application requires buck converters with very low quiescent current for low power consumption during idle mode, but also good load transient behaviour and high efficiency during the high load condition. The RT5706 and RT5707/A family is designed to achieve 360nA idle mode operation, while the HCOT control ensures fast transient behaviour. The Low Rdson internal MOSFETs provides high efficiency during pulse loads. RT5706 contains an extra load switch which can be used to disable subsystems for ultra low power standby mode. The tiny CSP 8B-0.9x1.6 package ensures a small application footprint. RT5706 and RT5707 are sampling now. For more information, please contact your nearest Richtek sales office.

Sensitive devices like accelerometers sensors and touch-screen controllers require stable noise-free supplies, and these will normally use low drop linear regulators. Richtek’s low Iq LDO’s like RT9073A are highly suitable for wearable applications: They have 1μA ground current, but can also provide quick transient response due to their dynamic ground current control. Stable with only 1μF output capacitors and housed in tiny 1x1 ZQFN packages ensures small application footprint.

Charging various sizes low capacity Li-Ion battery cells requires a charger IC with a wide charge current adjustment range. At the same time all charge parameters like pre-charge current and end-of-charge current need to track with the programmed current. Another important parameter is the charger leakage current in sleep mode.

RT9527GQW is specifically designed for charging low capacity Li-Ion batteries with a charge current adjustment range between 10mA to 600mA which makes it suitable for a wide range of small size batteries. It features accurate 4.2V CV regulation voltage, 10% ratio tracking pre-charge and end-of-charge current, 300nA sleep mode, build-in safety timer and NTC sense, all integrated in a small 2x2 QFN package. This 28V input rated part can be used in virtually any charger application for small hand-held and wearable solutions.

Remaining battery capacity can be accurately sensed by means of the battery gauges which make use of the battery voltaic model. These systems measure the dynamic battery voltage and calculate the Relative State Of Charge. This method does not suffer accumulation errors which are typical for coulomb counting systems. RT9428WSC reports RSOC to the system controller via I2C and consumes only 1μA in sleep mode. It requires only one capacitor, and is housed in a tiny CSP8B 1.6x1.52mm package for smallest footprint.

All registered trademarks and other trademarks belong to their respective owners. For more details, please visit RICHTEK official site.