Ricoh Electronic Devices Co., Ltd. in Japan has launched two VFM mode Buck DC/DC Converters RP511 and RP512, designed to use in wearable devices and applications for Internet of Things (IoT) requiring low current consumption to extend battery life. Additionally, the products also feature a minimum of external components and are available in a small package to reduce circuit board space.
Today’s wearable and IoT devices mainly operate in a sleep mode and therefore power consumption is significantly defined by the quiescent current which refers to a circuit’s quiet state, not driving any load. In this mode, the system is idle but ready to wake up at any time to perform a task, transmitting some data and resume to sleep mode again.
The RP511 and RP512 have an impressive low quiescent current and consume only 300 nA, prolonging battery life or makes it possible for the designer to select a smaller sized battery for the application. The difference between the two products is their output current capability, they can provide respectively 100 and 300 mA. Both products offer synchronous rectification and have high and low side MOSFET driver transistors embedded, eliminating the need for an external diode in the circuit. As for the available packages, one can select from a SOT-89-5, DFN2527-10 and the smallest solution is provided by the product in a WLCSP-8-P1 package. With three external components it occupies in total only 8.0 or 10.6 mm2 of circuit board area.
The DC/DC Converters operate in a VFM mode which is best to achieve a high efficiency performance at low output current demands, the peak efficiency is around 95 per cent.
A number of protection circuits are integrated, such as an Under Voltage Lock-Out circuit disabling the DC/DC Converter in case the input voltage drops below a minimum threshold. A soft-start circuit controls the output voltage to ramp-up smoothly and prevents any output overshoot and undershoot during the start-up period. The Lx current limit circuit prevents the peak current through the inductor to exceed a specific maximum current threshold.
The RP511 and RP512 have an optional auto-discharge function, this feature rapidly discharges the output capacitor once the chip is disabled by the CE pin.