RC4391 Datasheet | Fairchild Semiconductor

.fairchildsemi. Inverting and Step-Down Switching Regulator Features - Versatile - Inverting function (+ to -) Step-down function Adjustable output voltage Regulates supply changes - Micropower - Low quiescent current - 170 m A Wide supply range - 4V to 30V - High performance - High switch current - 375 m A High efficiency - 70% typically - Low battery detection capability - 8-lead mini-DIP or S.O. package Description Fairchild Semiconductor’s RC4391 is a monolithic switch mode power supply controller for micropower circuits. The RC4391 integrates all the active functions needed for low power switching supplies, including oscillator, switch, reference and logic, into a small package. Also, the quiescent supply current drawn by the RC4391 is extremely low; this bination of low supply current, function, and small package make it adaptable to a variety of miniature power supply applications. The RC4391 plements another Fairchild Semiconductor switching regulator IC, the RC4190. The RC4190 is dedicated to step-up (VOUT > VIN) applications, while the RC4391 was designed for inverting (VOUT = -VIN) and step-down (VOUT < VIN) applications. Between the two devices the ability to create all three basic switching regulator configurations is assured. Refer to the RC4190 data sheet for information on step-up applications. The functions provided are: Block Diagram RC4391 LBR C2 Q2 C1 VFB - - - - - - Squarewave oscillator (adjustable externally) Bandgap voltage reference High current PNP switch transistor Feedback parator Logic for gating the parator Circuitry for detecting a discharged battery condition (in battery powered systems) VREF LBD +1.25V REF/Bias OSC Q1 Gnd CX VREF +VS Few external ponents are required to build a plete DC-to-DC converter: - - - - - Inductor Low value capacitor to set the oscillator frequency Electrolytic filter capacitor Steering diode Two resistors 65-3471-01 Rev....