Application Hint 43c Micrel Application Hint 43c 89% Efficient RF Bias Circuit by William Mai Circuit Performance • RF applications • High efficiency at light load • Output ripple voltage <100mV L1 120µH VIN +2.7V to +4.2V U1 MIC2142 C1 10µF 6.3V VCC R3 1M SW D1 MBR0520 R1 453k FB EN GND C2 1µF VOUT 6V/6mA C4 270pF R2 124k C3 10µF 6.3V GND GND VIN V IIN mA VOUT V IOUT mA Eff % 2.7V 15.3mA 6.0V 6.11mA 89 4.2V 10.0mA 6.0V 6.30mA 90 Figure 2. Typical Output Data Figure 1. High Efficiency Circuit Bill of Materials Item Part Number Manufacturer Description C1,C3 GRM40X5R106K6.3 Murata1 10µF/6.3V Ceramic 2 C2 GRM235Y5V105Z25 Murata1 1µF/25V Ceramic 1 GRM40COG271K050AB Murata1 270pF/50V Ceramic 1 C4 D1 L1 R1 R2 R3 U1 Semiconductor2 Qty MBR0520 On 0.5A 20V Schottky Rectifier 1 CDC5D23-121K Sumida3 120µH 1 CRCW08054533FRT1 Vishay-Dale4 453k 1% 1/10W, size 0805 1 CRCW08051243FRT1 Vishay-Dale4 124k 1% 1/10W, size 0805 1 CRCW08051004JRT1 Vishay-Dale4 1M 5% 1/10W, size 0805 1 MIC2142BM5 Micrel5 Micropower Boost Converter 1 Note 1. Murata, tel: 949-916-4000 Note 2. On Semiconductor, tel: 800-344-3860 Note 3. Sumida, tel: 510-668-0660 Note 4. Vishay-Dale, tel: 207-324-4140 Note 5. Micrel Semiconductor, tel: 408-944-0800 Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com August 2002 1 Application Hint 43c Application Hint 43c Micrel MICREL, INC. 1849 FORTUNE DRIVE TEL + 1 (408) 944-0800 FAX SAN JOSE, CA 95131 + 1 (408) 944-0970 WEB USA http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel, Inc. © 2002 Micrel, Incorporated Application Hint 43c 2 August 2002