The new R5441 and R5443 ICs from Ricoh are specifically designed for use in rechargeable smartwatches, hearing aid instruments, fitness trackers and wireless earbuds
Wearable devices have a small rechargeable Li-ion battery with a capacity in the range from 50 to 100 mAh. These batteries have some requirement for its internal components which are very challenging, such as ultra-small package size, low current consumption in On and Standby mode and also sophisticated safety circuits. To meet these requirements, Japanese multinational imaging and electronics company, Ricoh, has launched a single cell Li-Ion battery protection ICs in a Wafer Level Chip Scaled Package (WLCSP).
The R5441 and R5443 ICs are especially designed to use in rechargeable smart watches, hearing aid instruments, fitness trackers, wireless earbuds and other small portable devices.
With the board space of 1.05 mm2 and a thickness of 0.36 mm, R5443 is the smallest version of IC. At present, it is one of the smallest single cell Li-Ion protection ICs. As compared to other protection ICs it is 53% smaller in a 1.4 x 1.4mm DFN package.
R5441 / R5443 current consumption of the ICs is equal or lower than most other available solutions on the market ( 3.5 µA and 2.5 µA) and it contributes reducing the self-discharge rate of the battery pack.
As soon the battery voltage decreases below the over-discharge voltage threshold, the product enters a standby mode and disables several internal circuits to lower the current consumption to 0.04 µA, ensuring further discharge of the battery is kept to a minimum.
Generally Li-Ion batteries are safe , but in case of internal or mechanical malfunction it can become a potential hazard. In these situation protection IC monitors the charge and discharge process. Here are following processes that are monitored by protection ICs:
• Over-charge voltage: Battery voltage exceeds the charge threshold for a certain period
• Over-discharge voltage: Battery voltage exceeds the discharge threshold for a certain period
• Over-discharge current: Battery current exceeds the discharge threshold for a certain period
• Over-charge current: Battery current exceeds the charge threshold for a certain period
• Short current: Battery current exceeds the short discharge threshold for a certain period
Both the R5441 and R5443 have an improved over-charge voltage threshold accuracy of ±10 mV versus ±30 mV for regular products. The reason behind this feature is to increase the charge voltage while maintaining the same safety level. As a result, the battery voltage will increase with 40 mV and extends the battery lifetime, which is good for applications with a small battery capacity.
For higher standard of current sensing, the R5441 and R5443 make use of an external current sense resistor.
The R5441 has an additional circuit to monitor the temperature of the battery pack by connecting an external NTC resistor to the Tin pin.
Click here to know about detailed specifications and features of R5441 and R5443.