Designed for applications requiring ultra-low current consumption to extend battery life, the VFM mode Buck DC/DC Converters RP514 and RP515 by Ricoh Electronic Devices are equipped with an integrated battery voltage monitor to measure the remaining charge left in the battery. These Buck DC/DC Converters come with a built-in resistor divider and voltage follower as a buffer. This circuit has a lower current flow to the ground and the buffer output is compatible with the input impedance of the A/D converter. The components are integrated into the chip to reduce circuit board space and cost. Their low quiescent current enables to increase battery life or helps the designer select a smaller sized battery for the application. Regarding the output current capability, the RP514 delivers 100mA while the RP515 provides 300 mA.
Low quiescent current and power consumption of 300 nA
They both grant synchronous rectification and have high and low side MOSFET driver transistors embedded. Operating in a VFM mode, the peak efficiency is at around 95%. They comprise “Under Voltage Lock Out” circuit to disable the DC/DC Converters if the input voltage drops below a minimum threshold. Moreover, their soft-start circuit functionality controls the output voltage to ramp-up with a constant slope and prevents any output overshoot and undershoot during the start-up period. The Lx current limit circuit helps prevent the peak current through the inductor to overreach a specific maximum current threshold. Last, they have an optional auto-discharge function to quickly discharge the output capacitor to the ground once the CE pin disables the chip.
