Schematic for the MC34063 Buck SMD Demonstration Board h 9/9/2003 MC34063 Evaluation Board Design Example Buck Regulator (12V to 3.3V@100mA/500mA)(SMD) IC101 MC34063AD P101 Vin (+12Vin) Gnd C101 100uF 16V R101, Prov. R102 Prov. 5 Feedback Ground 4 6 Vcc 7 Ipk Sense Timing Cap. 3 Switch Emitter 2 8 Drive Collector Switch Collector 1 R103 Prov. C103 270pF R105 Prov. R104 Prov. R106 Prov. C102 0.1uF C106 Prov. C105 Prov. C104 Prov. C107 0.1uF P102 Vout (+3.3V) Gnd R108 4.12K, 1% No External Transistor Q101 (100mA Output Current) External Transistor Q101 (500mA Output Current) 09/09/2003 FB101 Prov. R110 Prov. R107 Prov. D101 MBRS140 R109 2.49K, 1% L102 Prov. L101 Prov. Q101 Prov. Q101 R101 R102 R103 R104 R105 R106 R107 C104 C105 L101 Out 1.5 ohms Out Out Out Out "0" ohm resistor Out 100uF 6.3V Out 330uH 1 ohm 1 ohm Out "0" ohm resistor Out 470 330uF 6.3V 330uF 6.3V 68uH PZT651 SOT-223 1 ohm Style 1 1 www.onsemi.com