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: 12mV_P-P
• Input-Voltage Ripple: 180mV_P-P
• Switching Frequency: 250kHz
• Efficiency: 82% with V_IN = 18V at 13.4A, 74% with V_IN = 36V at 13.4A.

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

Table 1. Bill of Materials

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.