MAXREFDES1050: -15V/1.5A buck-boost DC-DC converter using buck controller MAX17504

The MAXREFDES1050 is a positive input, negative output power supply that delivers up to 1.5A at -15V from a 18V to 30V supply voltage. It is designed for industrial control equipment that uses analog components like amplifiers and multiplexers that operate on negative supply voltage. Typically operating at ±12V, ±18V or other variations, these voltages are generated from a 24V DC bus. The MAXREFDES1050 illustrates techniques using the synchronous buck regulators to generate negative voltages. This document explains how the MAX17504 synchronous step-down converter can be used to generate -15V from 18V to 30V input voltage. An overview of the design specification is shown in Table 1. The MAX17504/MAX17504S high-efficiency, highvoltage, synchronously rectified step-down converter with dual integrated MOSFETs operates over a 4.5V to 60V input. Maxim’s portfolio of high-voltage synchronous buck regulators offers 50% lower power loss, which allows equipment to operate 50% cooler. The device features a peak-current-mode control architecture with a MODE feature that can be used to operate the device in pulsewidth modulation (PWM), pulse-frequency modulation (PFM), or discontinuous mode (DCM) control schemes. Built-in compensation across the output voltage range eliminates the need for external components. The feedback (FB) regulation accuracy over -40°C to +125°C is ±1.1%. 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. The device is available in a compact (5mm x 5mm) TQFN lead (Pb)-free package with an exposed pad. Simulation models are available.

This board is not available for purchase.

Designed, Built, Tested

This reference design describes the hardware shown in Figure 1. It provides a detailed systematic technical guide to design a buck-boost converter using Maxim’s MAX17504 step-down controller. The converter has been built and tested, details of which follow later in this document.

Design Resources