Runic low-power LDO RS3221 assists in the design of smart home sensors and MCU power supply, with small package size and low quiescent current as low as 1uA

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In smart home products, the core components are a variety of sensors and MCU. The power supply of these sensors and MCU requires a stable, low-noise, and high-precision power supply voltage, while also requiring small size and power consumption.


For the internal power supply design of smart home products, we recommend the domestic low-power LDO device RS3221 of Runic, using CMOS semiconductor technology, with an input voltage of 1.7-7.5V, an optional fixed output voltage from 0.8V to 5V, supporting an output current of 200mA. Below is  typical electrical parameters of RS3221.

Electrical Characteristic


Input Voltage


Maximum Output Current


Ground Pin Current


Dropout Voltage

160mV@200mA (Output Voltage—3.3V)




-40 to +85


SOT23-3SOT23-5SC70-5UTDFN 1x1-4

Many smart home products are powered by batteries or USB, which strictly require power consumption of internal devices. RS3221 has an ultra-low operating current of 1uA, which can improve battery utilization and extend product life.RS3221 uses 8V CMOS Process design, its wide input voltage can withstand the surge voltage of USB VBUS interface or other power interface hot plug, and meet the needs of USB and dual power supply.


RS3221 also has a variety of small-size packages, such as SOT23-3, SC70 -5, DFN1x1-4. Its own application circuit is simple, only a filter capacitor is needed, and the circuit design can be easily completed within the size of conventional smart home products. The following is the pin diagram and typical application circuit of RS3221.


Figure 1. Pin description of RS3221


Figure 2. Typical Application Circuit


In summary, low-power LDO RS3221 has the characteristics of 1uA quiescent current, 1.4-7.5V wide input voltage range, and small size package. It is suitable for the power supply design of smart home sensors and MCU.