Application Hint 39b Micrel Application Hint 39b 3.3V/150mA SEPIC Circuit by William Mai Circuit Performance • Efficiency >75% at 150mA • Output ripple voltage <100mV • Low-profile solution Efficiency vs. Output Current 80 L1 10µH GND EN FB 7 2 SS SGND 8 RSET PGND 0.01µF R2 50V 10k 4 C2 3 R3 1M R4 487k L2 10µH C4 10µF 6.3V 70 VIN = 3V 65 60 200 1 160 180 5 VIN = 4.2V 120 140 R1 100k SW VIN = 3.6V 60 80 100 C1 10µF 6.3V VDD 75 0 6 D1 C3 10µF/6.3V MBR0530T1 VOUT +3.3V 20 40 U1 MIC2145 EFFICIENCY (%) VIN +3V to +4.2V OUTPUT CURRENT (mA) Figure 2. Typical 3.3V Output Efficiency Figure 1. SEPIC Circuit Bill of Materials Item U1 C1, C3, C4 C2 D1 Part Number Manufacturer Description MIC2145BMM Micrel1 High Effciciency Boost Converter 1 GRM42-6X5R106K6.3 Murata2 10µF, 6.3V Ceramic 3 GRM40X7R103K50 Murata2 0.01µF, 50V Ceramic 1 0.5A, 30V Schottky Rectifier 1 Semiconductor3 Qty MBR0530T1 On MBRX0530 Micro Commercial Corp.4 0.5A, 30V Schottky Rectifier L1, L2 CR43-100 Sumida5 10µH Inductor 2 R1 CRCW06031003FRT1 Vishay-Dale6 100k, 1% resistor, size 0603 1 R2 CRCW06031002FRT1 Vishay-Dale6 10k, 1% resistor, size 0603 1 CRCW06031004FRT1 Vishay-Dale6 1M, 1% resistor, size 0603 1 CRCW06034873FRT1 Vishay-Dale6 487k, 1% resistor, size 0603 1 R3 R4 Note 1. Micrel Semiconductor tel: 408-944-0800 Note 2. Murata tel: 949-916-4000 Note 3. On Semiconductor tel: 800-344-3860 Note 4. Micro Commercial Corp. tel: 800-346-3371 Note 5. Sumida tel: 510-668-0660 Note 6. Vishay-Dale tel:402-644-4218 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 39b Application Hint 39b 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 39b 2 August 2002