With the rapid development of technology, smart rings, as an emerging smart wearable device, have drawn increasing attention from brand manufacturers. Chinese wearable manufacturer Huami released a new smart ring called Helio Ring during CES 2024. Samsung Electronics officially released the Galaxy Ring in July 2024, which received a warm response from the market.
The smart ring not only has the fashion attribute of decorative trendy products, but also serves as an auxiliary intelligent sensing accessory for smartphones, used for monitoring human health data. Compared with watches and bracelets, the ring closer to the skin, so it has an accuracy advantage in collecting basic human biological information such as the rhythm of the pulse, heart rate, blood oxygen, electrocardiogram, and body temperature, etc. Compared with smart watches, the ring also has the characteristic of wearing without feeling, which can better meet the differentiated needs of users.
The smart ring is limited by space size, and the equipped lithium battery capacity is usually between 15mAh and 23mAh, and the battery life needs to reach 5 days or longer. Therefore, chips with ultra-low power consumption and ultra-small size are bound to be favored by product developers.
Cellwise has launched multiple ultra-low power small-sized power chips. As shown in Figure 1, which are very suitable for smart ring applications.
Linear Charger-CW6308/CW6305/CW6307
The CW6308 is the linear charger with the smallest size in the industry that supports the I2C interface and power path management. It supports a maximum charging current of 320mA. The CW6308 could extend the battery life with its ultra low power consumption. After only being powered by the battery and enabling the Watchdog function, the chip has only 5μA quiescent current in normal mode and 500nA in ultra-low power mode. In ship mode, the IC only consumes 300nA.
The CW6305 and CW6307 has the similar features as the CW6308，but both support maximum charging current of 470mA.
The CW6308 is available in lead-free 0.4mm pitch, 1.25mm x 1.25mm, 9-ball WLCSP package. The CW6305 and CW6307 are available in lead-free 0.5mm pitch, 1.55mm x 1.55mm, 9-ball WLCSP package.
Fuel Gauge-CW2215
The CW2215 is a single-cell lithium battery fuel gauge with the industry's lowest power consumption of 5μA. It has a high-precision ADC for voltage, current and temperature detection. The chip has a built-in "FastCali" algorithm. Combined with the battery characteristic parameters from the Battery Characterization, it can accurately calculate the remaining capacity (SOC), cycle count (Cycle) and battery health (SOH), and can be configured to report interrupts in case of low power, high temperature or low temperature. The IC is available in Lead-free 0.5mm pitch, 1.58mmx1.53mm, 9-ball WLCSP package.
Low-Dropout Linear Regulator-CW6004
The CW6004 is a 200mA ultra-low quiescent current LDO. The quiescent current is as low as 300nA. The input voltage ranges from 1.6V to 5.5V. The output voltage is selectable from 1.1V, 1.2V, 1.5V, 1.8V, 2.5V, 2.8V, 3.0V and 3.3V. The CW6004 has a fast response to ensure the stability of the output voltage when the device quickly switches from standby and light load to heavy load. The IC is available in DFN-4, 1.0mm x 1.0mm package.
Figure 2. CW6004 Quiescent Current vs Input Voltage
Figure 3.
CW6004 Ground Current vs. Output Current
Buck Converter-CW6602/CW6603
The CW6602 is an ultra-low quiescent current buck converter with an input voltage range from 2.15V to 5.5V and 8 selectable voltage outputs range from 1.2V to 3.3V. The quiescent current is as low as 330nA, and its load current is 0.6A Max. When the output voltage is 1.8V, the heavy load efficiency of the chip is over 90%, and the light load efficiency of 100μA can also reach 85%. The chip has a fast load dynamic response capability. The device is available in a tiny lead-free 0.4mm pitch,1.575mm x 0.825mm, 8 ball WLCSP package.
CW6603 has the same functions and package size as the CW6602. The difference is that the output voltage range is 0.6V to 1.2V.
Figure 4. CW6602 Vout=1.8V Efficiency
Load Switch-CW3301
The CW3301 is a load switch with an ultra-low MOS on-resistance and maximum current up to 2.0A with input voltage range from 1.1V to 5.5V. The output voltage slew rate of the chip is controlled to effectively protect the subsequent chips. It has an industry-leading 5nA on-state quiescent current and a 12nA off-state leakage current. It supports optional fast output discharge. The IC is available in a tiny lead-free 0.4mm pitch, 0.76mm x 0.76mm, 4-ball WLCSP package.
Battery Protection IC-CW1011
The CW1011 is single-cell lithium battery protection chip that supports high-precision overvoltage, undervoltage, charge overcurrent, discharge overcurrent and short circuit protection. The chip integrates dual MOSFETs with an on-resistance of 54 mohm internally. The quiescent current is 2.5μA and it supports sleep mode with a power consumption as low as 20nA. The IC is available in tiny DFN-6L, 1.5mm x 2.0mm package.
Cellwise has been deeply engaged in ultra-low power consumption technology for many years and has numerous design wins in wearable devices and digital accessories such as smart watches, TWS earphones, active styluses, and wireless Bluetooth keyboards and mouses. The power IC introduced today will definitely help brand manufacturers and solution developers achieve smaller space stacking, longer battery life, and better user experience for smart rings.
Thank you for your continued attention to Cellwise and our products.