MAXREFDES1039: 64W and 48W dual output DC-DC Buck converters

The MAX17559 is a dual-output, synchronous step-down controller that drives nMOSFETs. The device uses a constant- frequency, peak-current-mode architecture. The two outputs can be configured as independent voltage rails. Input capacitor size is minimized by running the two outputs 180° out of phase. The IC supports current sensing using either an external current-sense resistor for accuracy or an inductor DCR for improved system efficiency. Current foldback or latch-off limits MOSFET power dissipation under short-circuit conditions. The IC provides independent adjustable soft-starts/stops for each output and can start up monotonically into a pre-biased output. The IC can be configured in either PWM or DCM modes of operation, depending on whether constant-frequency operation or light-load efficiency is desired. The IC operates over the -40°C to +125°C temperature range and is available in a lead(Pb)-free, 7mm x 7mm, 32-pin TQFP, package.

Key Features

• Wide 4.5V to 60V Input Voltage Range
• Wide 0.8V to 24V Output Voltage Range
• RSENSE or Inductor DCR Current-Sensing
• Fixed 180° Out-of-Phase Operation
• Adjustable 100kHz to 2.2MHz Switching Frequency
• Independent Enable and PGOOD
• Available in a Lead(Pb)-Free 7mm x 7mm, 32-Pin TQFP Package
• Enhances Power Efficiency
• Low-Impedance Gate Drives for High Efficiency
• DCM Operation at Light Loads
• Auxiliary Bootstrap LDO
• Operates Reliably in Adverse Industrial Environments
• Independent Adjustable Soft-Start/Stop or Tracking
• Current Selectable Foldback or Latch-off Limits
• MOSFET Heat Dissipation During a Short-Circuit Condition
• Operates Over the -40°C to +125°C Temperature Range
• Output Overvoltage and Overtemperature Protections

This board is not available for purchase.

An offline DCM flyback converter using the MAX17595 is demonstrated for a 4.5V DC output application. The power supply delivers up to 4.5A at 4.5V.

Designed, Built, Tested

This document describes the hardware shown in Figure 1. It provides a detailed systematic technical guide to designing a dual output buck converter using the Maxim MAX17559 current-mode controller. The power supply has been built and tested, details of which follow later in this document.

Design Resources