Switching Regulator IC - RH5RH/5RI Series

Boost-specific fixed output switching regulator IC - RH5RH/5RI series

In portable electronic devices (typically MP3 players), only one or two batteries are often used for power supply. In such circuit systems, when it is desired to use an integrated circuit with a working power supply of 5V or an LCD power supply is essential, the most suitable method is to use a boost IC.

The RH5RH/5RI series (Ricoh, Japan) is a fixed output switching regulator IC for boosting voltage. It only needs three external components: inductor, diode and capacitor to obtain a fixed boost output. The most excellent feature of this circuit is that it has very low power consumption (4~15uA) and can still work normally even at a low input voltage of 0.9V.

The RH5RI and RH5RH series are frequency modulation (PFM) and pulse width modulation (PWM) three-terminal step-up switching regulator ICs, respectively. They are available in two types: the RH5RIxx1 (RH5RHxx1) series with the driver included in the IC chip and the RH5RIxx2 (RH5RHxx2) series with an external driver. The former is suitable for circuits with load changes from no load to several mA, while the latter is suitable for circuits with load changes from several mA to hundreds of mA.

The RH5RH/5RI series ICs are characterized by low power consumption, with no-load power consumption of only 4~15uA, a starting operating voltage of only 0.9V, an efficiency greater than 80%, and a small SOT-89 chip package.

The figure below shows the basic external circuit diagram of RH5RI and RH5RH. It can work normally by connecting only three external components: inductor L1, diode VD1 and capacitor C1.

The recommended value of the inductor is 82~270uH, and the diode should be a Schottky diode. The capacitor is preferably a tantalum capacitor. When a larger load must be driven, an external driver circuit as shown in the figure below can be used.