Reference Design for a High-In

Reference Design for a High-Input-Voltage, High-Output-Current Buck Controller Using the MAX15046

Abstract: This reference design presents a circuit for using the MAX15046 step-down power-supply controller for high-input-voltage, low-output-voltage applicaTIons that require high output current.

The reference design presents a schemaTIc (Figure 1), bill of materials (Table 1), and performance characterisTIcs (Figures 2–7). Key specificaTIons of the MAX15046 are listed below.

Design Specifications and Setup

• Input Voltage: 18V to 36V
• Output Voltage: 1.2V
• Output Current: 13.4A
• Output-Voltage Ripple: 12mVP-P
• Input-Voltage Ripple: 180mVP-P
• Switching Frequency: 250kHz
• Efficiency: 82% with VIN = 18V at 13.4A, 74% with VIN = 36V at 13.4A.

More detailed image (PDF, 256kB)
Figure 1. Schematic of the MAX15046 buck power supply at FSW = 250kHz.

Table 1. Bill of Materials Designator Value Description Part Number Manufacturer Package Quantity C1 470µF/50V Capacitor EEVFK1H471M Panasonic Electrolytic 1 C2 0.1µF/50V Capacitor GRM188R71H104K Murata 603 1 C3 1µF/50V Capacitor GRM21BR71H105K Murata 805 1 C4 4.7µF/6.3V Capacitor GRM188R60J475K Murata 603 1 C5 2.2µF Capacitor GRM188R60J225K Murata 603 1 C6, C7, C7X 10µF/50V Capacitor GRM55DR70H106K Murata 2220 3 C8 0.47µF/16V Capacitor GRM188R71C474K Murata 603 1 C9 2700pF/50V Capacitor GRM2165C1H272JA Murata 805 1 C10 470µF/6.3V Capacitor EEFSX0D471E4 Panasonic 7.3mm x 4.3mm x 1.9mm 1 C11 100µF/6.3V Capacitor GRM32ER60J107ME20L Murata 1210 1 C12 100µF/6.3V Capacitor GRM32ER60J107ME20L Murata 1210 1 C13 68pF/50V Capacitor GRM1885C1H680J Murata 603 1 C14 100pF/50V Capacitor GRM39COG101J50D500 Murata 603 1 C15 10nF/50V Capacitor GRM188R71H103KA01D Murata 603 1 C16 820pF/50V Capacitor GRM39COG821J50D500 Murata 603 1 C17 Open Capacitor         C18 22µF/6.3V Capacitor GRM31CR70J226KE19L Murata 1206 1 C19 1µF/6.3V Capacitor GRM188R70J105KA01D Murata 603 1 R3 10Ω Resistor Resistor Multisource 603 1 R4 51kΩ Resistor Resistor Multisource 603 1 R5 2.2Ω Resistor Resistor Multisource 603 1 R7 1Ω Resistor Resistor Multisource 603 1 R8 Open Resistor         R9 19.1kΩ Resistor Resistor Multisource 603 1 R10 6.04kΩ Resistor Resistor Multisource 603 1 R11 4kΩ Resistor Resistor Multisource 603 1 R12 86.6kΩ Resistor Resistor Multisource 603 1 R13 86.6kΩ Resistor Resistor Multisource 603 1 R14 68.1kΩ Resistor Resistor Multisource 603 1 R15 49.9Ω Resistor Resistor Multisource 603 1 R16 0 Resistor Resistor Multisource 603 1 R17 0 Resistor Resistor Multisource 603 1 L1 2.2µH/20A Inductor IHLP5050EZER2R2M01 Vishay 13.20mm x 12.90mm x 5.00mm 1 N1 60V, 6.2A n-Channel MOSFET SI7850DP Vishay PowerPAK® SO-8 1 N2 60V, 18.5A n-Channel MOSFET SI7478DP Vishay PowerPAK SO-8 1 D1 0.5A, 60V Schottky diode ZHCS506TA Zetex SOT23 1 U1 MAX15046 PWM Controller MAX15046 Maxim 16 PIN TQFN 1

Performance Characteristics

Figure 2. Total system efficiency versus load current relative to different input voltages.


Figure 3. Steady-state input voltage, output voltage, and gate signal.
Ch1: Switching-Node Voltage
Ch2: Input Voltage
Ch3: Output Voltage


Figure 4. Steady-state peak-to-peak input ripple and peak-to-peak output ripple.
Ch2: Input-Voltage Ripple
Ch3: Output-Voltage Ripple


Figure 5. Soft-start when VIN = 28V is applied with a 13.4A load.
Ch2: Input Voltage
Ch3: Output Voltage


Figure 6. Soft-stop when input power is off.
Ch2: Input Voltage
Ch3: Output Voltage


Figure 7. Output voltage and gate signal when the load is short circuited.
Ch3: Output Voltage
Ch4: Gate Signal of High-Side Switch

Board Layout

More detailed image (PDF, 4.7MB)
Figure 8. Two-layer layout of the reference design using the MAX15046 step-down power supply.