System Board 6481

MAXREFDES1019: Single-Input to Multiple-Input Buck Converter Circuit Using MAX17541G and MAX17504


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Input Type VIN (MIN)
(V)
VIN (MAX)
(V)
IOUT
(A)
Single/Multiple
Output
VOUT
(V)
POUT
(W)
Isolated/Non-Isolated Topology
DC 24 24 0.05 to 2 Multiple -20 to 20 1 to 40 Non-Isolated Synchronous Buck

This document describes a circuit that uses three MAX17541G buck converters and one MAX17504 step-down DC-DC converter. The circuit is arranged so that each buck converter uses the same input with four separate outputs. Each output has a different power specification. The MAX17541G regulator and features are given first, followed by the MAX17504 features.

MAX17541G

The MAX17541G high-efficiency, high-voltage, synchronous step-down DC-DC converter with integrated MOSFETs operates over a 4.5V to 42V input. The converter can deliver up to 500mA and generates output voltages from 0.9V up to 0.92 x VIN. The feedback (FB) voltage is accurate to within ±1.7% over the -40°C to +125°C operating temperature range. The MAX17541G uses peak-current-mode control with pulse-width modulation (PWM) and operates with fixed 600kHz switching frequency at any load.

Key Features

  • Reduced Power Dissipation
  • Peak Efficiency > 90%
  • Shutdown Current = 0.9μA (typ)
  • Operates Reliably in Adverse Industrial Environments
  • Hiccup-Mode Current Limit, Sink Current Limit, and Autoretry Startup
  • Built-In Output-Voltage Monitoring (Active-Low RESET Pin)
  • Programmable EN/UVLO Threshold
  • Adjustable Soft-Start and Prebiased Power-Up
  • -40°C to +125°C Ambient Operating Temperature Range/-40°C to +150°C Junction Temperature Range

MAX17504

The MAX17504 is also a high-efficiency, high-voltage, synchronous step-down DC-DC converter with integrated MOSFETs and operates over a 4.5V to 60V input. The converter can deliver up to 3.5A current. Output voltage is programmable from 0.9V to 0.9 x VIN. The feedback voltage regulation accuracy over -40°C to +125°C is ±1.1.%. The MAX17504 also features a peak-currentmode control architecture. The device can be operated in the pulse-width modulation (PWM), pulse-frequency modulation (PFM), or discontinuous-conduction mode (DCM) control schemes. A programmable soft-start feature allows users to reduce input inrush current. The device also incorporates an output enable/undervoltage lockout pin (EN/UVLO) that allows the user to turn on the part at the desired input voltage level. An open-drain active-low RESET pin provides a delayed power-good signal to the system upon achieving successful regulation of the output voltage.

Key Features

  • 100kHz to 2.2MHz Adjustable Switching Frequency with External Synchronization
  • Peak Efficiency > 90%
  • PFM and DCM Modes Enable Enhanced Light-Load Efficiency
  • 2.8μA Shutdown Current
  • Operates Reliably in Adverse Industrial Environments
  • Hiccup Mode Overload Protection
  • Adjustable Soft-Start and Prebiased Power-Up
  • Built-In Output-Voltage Monitoring with RESET
  • Programmable EN/UVLO Threshold
  • -40°C to +125°C Ambient Operating Temperature Range/-40°C to +150°C Junction Temperature Range
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A multiple buck converter circuit using three MAX17541G devices (VOUT1,2,3) and one MAX17504 device (VOUT4) is demonstrated for a single 24V input application. The power supply delivers up to four separate outputs.

Designed, Built, Tested

This document describes the hardware shown in Figure 1. It provides a detailed systematic technical guide to designing a buck converter circuit using Maxim’s MAX17541G and MAX17504 current-mode controllers. The power supply has been built and tested, details of which follow later in this document.

Design Resources

 
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MAX17541G
42V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter

  • Reduces External Components and Total Cost
  • Reduces Number of DC-DC Regulators to Stock
  • Reduces Power Dissipation

MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation

  • Eliminates External Components and Reduces Total Cost
  • Reduce Number of DC-DC Regulators to Stock
  • Reduce Power Dissipation