Analog Devices Inc./Maxim Integrated MAX256EVKIT+

Overview

MAX256EVKIT+ from Maxim Integrated is an evaluation kit for the MAX256 3W primary-side H-bridge driver IC, designed to simplify development of isolated DC-DC power supplies using transformer-based topologies. It supports +3.3V or +5V input, delivers up to 3W to the transformer primary, and enables rapid validation of internal oscillator (100kHz–1MHz) or external clock (up to 2MHz) operation with fixed 50% duty cycle output on ST1/ST2.

For engineers reviewing the MAX256EVKIT+ datasheet, MAX256EVKIT+ pinout, MAX256EVKIT+ application, or MAX256EVKIT+ equivalent, this kit provides pre-tested hardware, documented reference schematics (e.g., +5V-to-isolated-±15V), thermal performance validation, and configurable mode selection (MODE/CK_RS) to accelerate design of automotive-grade (-40°C to +125°C), medical, and industrial isolated power rails.

Technical Context

The MAX256EVKIT+ implements the MAX256 IC in a functional isolated power supply configuration, featuring a Halo TGM-H281NF center-tapped transformer and MBRS140 Schottky rectifiers. It validates break-before-make switching, undervoltage lockout (1.8V threshold), and thermal shutdown (165°C) under real load conditions.

It demonstrates dual-mode clocking: internal resistor-programmable oscillator (via CK_RS-to-GND resistor) and external clock mode with watchdog timeout (55µs). The board includes proper decoupling (4.7µF + 470nF at VCC), exposed paddle grounding, and layout practices that minimize parasitic coupling between ST1/ST2 and CK_RS.

Key Specifications

Availability

MAX256EVKIT+ is available at Aetrix Electronics and suitable for isolated communications links, medical equipment power rails, and industrial process control systems requiring stable component supply and fast prototyping support.

Supply support for MAX256EVKIT+ 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 high-performance analog, mixed-signal, and power management solutions for demanding applications.

The MAX256 product line targets compact, robust isolated power generation in space-constrained environments - engineered specifically for automotive, medical, and industrial systems needing reliable galvanic isolation without optocouplers or secondary-side controllers.

FAQ

What is the MAX256EVKIT+ used for?

The MAX256EVKIT+ is an evaluation kit for the MAX256 H-bridge driver IC. It enables rapid development and validation of isolated DC-DC power supplies using transformer-based topologies. Engineers use the MAX256EVKIT+ to verify +3.3V/+5V input operation, configure internal or external clock modes, measure ST1/ST2 drive capability, assess thermal performance under load, and validate reference designs such as +5V-to-isolated-±15V (Figure 10) before committing to custom PCB layout.

Does the MAX256EVKIT+ include the MAX256 IC?

Yes, the MAX256EVKIT+ includes one populated MAX256ASA+ IC in an 8-pin SO-EP package. This is the automotive-grade version specified for -40°C to +125°C operation and features the exposed paddle thermally connected to the board's ground plane. The MAX256EVKIT+ does not require additional IC purchase to begin evaluation.

Can the MAX256EVKIT+ generate regulated outputs?

Yes - the MAX256EVKIT+ supports regulated isolated outputs when combined with external LDOs or regulators. Reference circuits in the MAX256 datasheet demonstrate +3.3V-to-isolated-+5V using MAX1659, +5V-to-isolated-+3.3V using MAX1658, and +5V-to-isolated-±15V using dual 7815 regulators - all validated on the MAX256EVKIT+ platform with appropriate component substitutions.

What transformer is used on the MAX256EVKIT+?

The MAX256EVKIT+ uses the Halo Electronics TGM-H281NF center-tapped transformer (1:2.6CT turns ratio) for its default +5V-to-isolated-+5V configuration (Figure 8). This transformer meets the required ET product (≥42.3Vµs at +5.5V VCC, 65kHz min frequency) and supports push-pull rectification. Alternate transformers like TGM-280NS are also compatible for ±15V outputs (Figure 5).

How do I configure the MAX256EVKIT+ for external clock mode?

To configure the MAX256EVKIT+ for external clock mode, set the MODE jumper to GND and apply a clean square-wave clock signal (0.2–2MHz) to the CK_RS test point. The MAX256EVKIT+ will then switch ST1/ST2 at half the input frequency with guaranteed 50% duty cycle. The onboard 165kΩ internal pulldown ensures safe default behavior, and the watchdog disables the MAX256 if the clock stalls beyond 55µs.