REFERENCE SCHEMATIC 4376

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

By:  Murali Krushna

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.
Figure 1. Schematic of the MAX15046 buck power supply at FSW = 250kHz.
More detailed image
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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 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 2. Total system efficiency versus load current relative to different input voltages.

Figure 3. Steady-state input voltage, output voltage, and gate signal.
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.
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.
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.
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.
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

Figure 8. Two-layer layout of the reference design using the MAX15046 step-down power supply.
More detailed image
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Figure 8. Two-layer layout of the reference design using the MAX15046 step-down power supply.

PowerPAK is a registered trademark of Siliconix Inc., a wholly owned subsidiary of Vishay Intertechnology.



Related Parts
MAX15046 40V, High-Performance, Synchronous Buck Controller Samples  


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© Nov 04, 2009, Maxim Integrated Products, Inc.
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APP 4376: Nov 04, 2009
REFERENCE SCHEMATIC 4376, AN4376, AN 4376, APP4376, Appnote4376, Appnote 4376