Analog Devices Inc./Maxim Integrated MAXREFDES121C#

Overview

MAXREFDES121C# from Maxim Integrated is an isolated 24V-to-3.3V, 33W (10A) industrial power supply reference design based on the MAX17599 active-clamp forward controller. It delivers peak efficiency of 90.82% at 24V input, operates across 18V–36V input range, switches at 250kHz, and fits on a compact 70mm × 20mm board with functional insulation for harsh environments.

For engineers reviewing the MAXREFDES121C# datasheet, MAXREFDES121C# pinout, MAXREFDES121C# application, or MAXREFDES121C# equivalent, this reference design supports rapid prototyping of isolated 3.3V rails in PLCs, industrial sensors, telecom/datacom systems, and embedded computing where compact size, EMI control via frequency dithering, and hiccup-mode overcurrent protection are critical.

Technical Context

The MAXREFDES121C# implements an active-clamp forward converter topology using the MAX17599 PWM controller, enabling zero-voltage switching via programmable dead time between main (NDRV) and auxiliary (AUXDRV) drivers. It employs a p-channel/n-channel MOSFET primary stage (P1/N3) and synchronous rectification (N1/N2) on the secondary side.

Feedback uses a TL431V shunt regulator and 3000V optocoupler for isolation. Protection includes EN/UVLO (18V start), OVI (36V shutdown), soft-start, soft-stop clamp discharge, negative current limiting, and OTP thermal shutdown - all integrated into the controller IC and validated across line/load transients.

Key Specifications

Availability

MAXREFDES121C# is available at Aetrix Electronics and suitable for programmable logic controllers (PLCs), industrial process control systems, and telecom/datacom power supplies requiring stable component supply, fast time-to-prototype, and production-ready reference designs.

Supply support for MAXREFDES121C# includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in analog, mixed-signal, and power-management solutions for industrial, automotive, and communications applications.

The MAXREFDES reference design series targets rapid development of certified, test-validated power architectures - specifically engineered for robustness, compactness, and ease of integration in harsh industrial environments.

FAQ

What is the input voltage range supported by the MAXREFDES121C# reference design?

The MAXREFDES121C# supports an input voltage range of 18V to 36V DC, optimized for nominal 24V industrial bus systems. This range ensures reliable operation during brownout conditions and accommodates typical supply tolerances. The EN/UVLO threshold is set to 18.2V, and overvoltage protection triggers at 36.3V - both programmable via external resistor dividers on the MAX17599 controller used in the MAXREFDES121C# design.

Does the MAXREFDES121C# include output overvoltage or overcurrent protection?

The MAXREFDES121C# implements hiccup-mode overcurrent protection and thermal shutdown via the MAX17599 controller, but it does not include dedicated output overvoltage protection circuitry. Output regulation relies on the optocoupler-based feedback loop with TL431V reference. For systems requiring OVP, external supervision or downstream protection must be added - the MAXREFDES121C# design prioritizes input-side fault handling (EN/UVLO, OVI, OTP) and robust transient response instead.

Can the MAXREFDES121C# be used as a drop-in module on a host PCB?

Yes - the MAXREFDES121C# is designed as a space-optimized, module-style board with high-current pins for direct mounting onto a host PCB. Its 70mm × 20mm footprint and through-hole power terminals enable mechanical and electrical integration without custom connectors. However, it is not a sealed, fully encapsulated module; users must ensure adequate clearance, airflow, and EMI shielding per their end application when integrating the MAXREFDES121C#.

What is the measured output ripple and transient performance of the MAXREFDES121C#?

At full 10A load and 24V input, the MAXREFDES121C# delivers ±40mV peak-to-peak output ripple (ripple + spike). Load transients show ±120mV deviation: stepping from 5mA to 4A induces one transient spike, and stepping from 6A to 10A induces another - both with fast recovery. These values were verified per lab measurements documented in the official MAXREFDES121# design files and confirm suitability for noise-sensitive digital loads.

Is frequency dithering enabled by default on the MAXREFDES121C#?

No - frequency dithering is not enabled by default on the MAXREFDES121C#. The design operates at a fixed 250kHz switching frequency. However, the MAX17599 controller supports optional spread-spectrum operation via external components (e.g., capacitor on the FREQ pin), allowing users to implement low-EMI dithering if required for specific regulatory or system-level EMI constraints in their MAXREFDES121C# deployment.