PWM Step-down DC/DC Converter With Switch Function

The R5220D R5220K Series are CMOS-based PWM Step-down DC/DC Converters with synchronous Rectifier low supply current and LDO mode. DC/DC converter of the R5220D R5220K consists of an Oscillator a PWM control circuit, a reference voltage unit, an error Amplifier a soft-start circuit, protection circuits, a protection against miss operation under low voltage (UVLO), PWM-DC to DC converter / LDO alternative circuit, a chip enable circuit, and a driver Transistor A high efficiency Step-down DC/DC converter CAN be easily composed of this IC with only a few kinds of external components, or an inductor and capacitors. LDO of the R5220x consists of a vortage reference unit, an error Amplifier resistors for voltage setting, output current limit circuit, a driver Transistor and so on. The output voltage is fixed internally in the R5220x. The output voltage of the DC/DC converter and the LDO CAN be set independently. PWM Step-down DC/DC converter / LDO alternative circuit is active with Mode Pin of the R5220x Series. Thus, when the load current is small, the operation CAN be switching into the LDO operation from PWM operation by the Logic of MODE pin and the consumption current of the IC itself will be small at light load current. As protection circuits, the current limit circuit which limits peak current of Lx at each Clock cycle, and the latch type protection circuit which works if the term of the over-current condition keeps on a certain time in PWM mode. Latch-type protection circuit works to latch an internal driver with keeping it disable. To release the protection, after disable this IC with a chip enable circuit, enable it again, or restart this IC with power-on or make the supply voltage at UVLO detector threshold level or lower than UVLO.
By RICOH Co.,Ltd.