Abstract: This application note shows a reference design using the MAX15026 low-cost, high-efficiency synchronous buck converter in an auxiliary power supply for LCD TVs or set-top boxes. This reference design generates a 5V, 5A power supply from a wide, 6.5V to 24V input voltage range. Key specifications for the reference design are listed below, along with a detailed schematic (Figure 1) and the bill of materials (Table 1) needed for this application. Specifications Input Voltage Range: 6.5V to 24V Output Voltage: 5V Output Current: 5A Output Voltage Ripple (pk-pk): 50mV Switching Frequency of Converter: 300kHz Overcurrent Protection Limit: 6A Efficiency: > 90% for Normal Operation Figure 1. Schematic of the MAX15026 synchronous buck converter for a 300kHz switching frequency. Table 1. Bill of Materials Designator Value Description Part Footprint Manufacturer Quantity C1 220µF, 35V Capacitor EEVFK1V221P 8mm x 10.2mm Panasonic 1 C2, C3 4.7µF, 50V Capacitor GRM31CR71H475KA12L 1206 Murata 2 C4 0.1µF, 50V Capacitor GRM188R71H104KA93D 0603 Murata 1 C5 4.7µF, 6.3V Capacitor GRM188R60J475KE19D 0603 Murata 1 C6 2.2µF, 6.3V Capacitor GRM188R60J225KE19D 0603 Murata 1 C7 1µF, 50V Capacitor GRM21BR71H105KA12L 0805 Murata 1 C8 0.47µF, 16V Capacitor GRM188R71C474KA88D 0603 Murata 1 C9, C16 1200pF, 50V Capacitor GRM1885C1H122JA01D 0603 Murata 2 C10, C11 47µF, 10V Capacitor GRM32ER71A476KE15L 1210 Murata 2 C12, C13, C14 22µF, 10V Capacitor GRM31CR71A226KE15L 1206 Murata 3 C15 560pF, 50V Capacitor GRM1885C1H561JA01D 0603 Murata 1 C17 22pF, 50V Capacitor GRM1885C1H220JA01D 0603 Murata 1 R1 10Ω Resistor SMD 1% Resistor 0603 Vishay 1 R2 10kΩ Resistor SMD 1% Resistor 0603 Vishay 1 R3, R6 2.2Ω Resistor SMD 1% Resistor 0603 Vishay 2 R4 15kΩ Resistor SMD 1% Resistor 0603 Vishay 1 R5 56.2kΩ Resistor SMD 1% Resistor 0603 Vishay 1 R7 3.57Ω Resistor SMD 1% Resistor 1206 Vishay 1 R8 102kΩ Resistor SMD 1% Resistor 0603 Vishay 1 R9 13.7kΩ Resistor SMD 1% Resistor 0603 Vishay 1 R10 2.74kΩ Resistor SMD 1% Resistor 0603 Vishay 1 R11 47.5kΩ Resistor SMD 1% Resistor 0603 Vishay 1 L1 10µH ±20%, 5.5A Inductor SLF12575T-100M5R4-PF 12.5mm x 12.5mm x 7.5mm TDK 1 N1 30V, 6.3A, 35.5mΩ—Q1; 30V, 8.6A, 16.5mΩ—Q2 Dual MOSFET FDS6982AS 8-SO Fairchild 1 U1 PWM Controller Low-Cost, DC-DC Synchronous Buck Controller with a 4.5V to 28V Operating Range MAX15026BETD+ 14-TDFN-EP Maxim 1 Performance Data Figure 2. Steady-state output voltage, input voltage, and switching-node voltage at VIN = 24V, VOUT = 5V. Ch1: VOUT; Ch2: VIN; Ch3: Lx Node Voltage Figure 3. Enable, soft-start, soft-stop and PGOOD sequence waveforms. Ch1: Enable; Ch2: VOUT; Ch3: PGOOD Figure 4. Output and input ripples at VIN = 24V, VOUT = 5V and IOUT = 5A. Ch1: Output Voltage Ripple; Ch2: Input Voltage Ripple Figure 5. Converter load transient response with a 2A step change in load current. Ch1: Output Voltage Dip; Ch2: Load-Step Change (1A/div) Test Conditions VIN = 12V, VOUT = 5V Load Current Step Change: 1A to 3A Load Current Slew Rate: 2A/µs Figure 6.Hiccup-mode overcurrent protection with output shorted. CH1: Output Voltage; CH2: Gate Pulses Figure 7. Efficiency vs. load current plots. Related Parts   APP 4365: Apr 15, 2009 MAX15026 Low-Cost, Small, 4.5V to 28V Wide Operating Range, DC-DC Synchronous Buck Controller Full Data Sheet (PDF, 320kB) Automatic Updates Would you like to be automatically notified when new application notes are published in your areas of interest? Sign up for EE-Mail™. We Want Your Feedback!   Download, PDF Format (159kB)  AN4365, AN 4365, APP4365, Appnote4365, Appnote 4365