MAX256

PRODUCTION

3W Primary-Side Transformer H-Bridge Driver for Isolated Supplies

Data Sheet (Rev. 2) Product Selection Table
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Overview

  • Simple, Flexible Design Provides Up to 3W to the Transformer in Isolated Power Supplies
    • Single Supply +5V or +3.3V Operation
    • Internal Resistor-Programmable Oscillator Mode
    • External Clock Mode with Watchdog
    • Disable Mode
  • Integrated System Protection
    • Undervoltage Lockout
    • Thermal Shutdown
  • Saves Space on Board
    • 8-Pin Thermally-Enhanced SO Package
MAX256
3W Primary-Side Transformer H-Bridge Driver for Isolated Supplies
MAX256: Typical Operating Circuit
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Documentation

Data Sheet 1

User Guide 5

Design Note 1

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Software Resources

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Hardware Ecosystem

Parts Product Life Cycle Description
Interface Transceivers 4
MAX13085E
PRODUCTION +5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485 Transceiver
MAX13082E
PRODUCTION +5.0V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485 Transceivers
MAX3072E
PRODUCTION +3.3V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceivers
MAX3075E
PRODUCTION +3.3V, ±15kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceivers
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Evaluation Kits

MAX256EVKIT

MAX256 Evaluation Kit

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Features and Benefits

  • +3V to +5VDC Input Range
  • Isolated Outputs
    • +VOUT: +5V Provides Up to 300mA
    • -VOUT: -5V Provides Up to 300mA
  • 87% Overall Efficiency at +5V Input and 200mA Load
  • Center-Tapped, Full-Wave Rectifier Output
  • 400kHz Switching Frequency
  • 2.7V Undervoltage Lockout (UVLO)
  • Designed for 1500VRMS Isolation
  • Low-Cost, Integrated-FET H-Bridge Design
  • Fully Assembled and Tested

Product Details

The MAX256 evaluation kit (EV kit) is a fully assembled and tested PCB that contains a 3W isolated H-bridge DC-DC converter. The circuit is configured for unregulated output voltages of approximately +5V and -5V (with respect to an isolated ground). Output current is up to 600mA from either output, or 300mA from each of the two outputs. Input power for the circuit is provided from a +5VDC source, or operates at any input voltage down to +3V with a corresponding reduction in the output voltages.

The EV kit provides greater than 85% overall efficiency at +5V between 250mW and 2W output power using an H-bridge DC-DC converter topology. Input ripple current and radiated noise are minimized by the inherent balanced nature of the design with no interruption in the input current. Undervoltage lockout (UVLO) and thermal shutdown provide for a robust 3W isolated supply. The surface-mount transformer provides up to 1500VRMS galvanic isolation with each output powered from a center-tapped full-wave rectifier circuit to reduce output voltage ripple.

Operation at 400kHz allows the use of ceramic output capacitors and a small transformer.

Applications

  • Industrial Process Control
  • Isolated Communications Links
  • Isolated Power Supplies
  • Medical Equipment
  • Telecommunications

MAXSANTAFEEVSYS

Evaluation Kit for the MAXREFDES5 4-Channel Analog Front End

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Features and Benefits

  • Self-Contained Easy Evaluation Kit for MAXREFDES5
  • Optimized AFE with Common Analog Input Ranges
  • Small Form Factor Test Platform
  • All Relevant Reference Design Files Included

Product Details

The MAXSANTAFEEVSYS kit allows users to quickly demonstrate and evaluate the functionality of the MAXREFDES5 4-channel 16-bit, isolated analog front end (AFE) reference design without the need for a bench power supply, signal generator equipment, or Xilinx development kit. The reference design board connects to a PC through an included USB-to-SPI adapter that provides both power and data communication to the board. To test the AFE reference design, a USB-powered signal generator board utilizing one of Maxim’s digital-to-analog converters (DAC) is also included. A Windows®-based graphical user interface (GUI) communicates with the boards for generating various analog signal test patterns and simplified access to AFE measurement data. 

The MAXREFDES5 reference design is a 4-channel analog front end (AFE) that accepts -10V to +10V, 0V to 10V, and 4–20mA current loop signals. The design integrates a 16-bit ADC with multirange input programmability (MAX1301) plus low-noise, high-impedance analog buffers (MAX9632) on two of the input channels and an ultra-high precision 4.096V voltage reference (MAX6126) to achieve maximum performance from the 16-bit system. A 600VRMS digital isolator (MAX14850) and 3W transformer driver (MAX256) provide the necessary isolated data and power connections to the host system. LDO regulators (MAX1659) provide regulated +12V, -12V, and 5V power rails to the analog front end.

EV Kit Contents
  • MAXREFDES5 4-Channel AFE Board
  • USB2PMB1 USB to Pmod™ Type 2A Adapter Board
  • MAX5216DACLITE Signal Generator Board
  • Two (2) Wires with Hook Clips (1 Red and 1 Black)
  • Two (2) USB Type A Male to USB Type B Mini Cables
  • USB Flash Drive with Documentation, GUI Applications, and USB Drivers

 

Applications

  • Industrial Data Acquisition
  • Programmable Automation Controllers (PAC)
  • Programmable Logic Controllers (PLC)
  • Proportional-Integral-Derivative (PID) Controllers
MAX256EVKIT
MAX256 Evaluation Kit
MAXSANTAFEEVSYS
Evaluation Kit for the MAXREFDES5 4-Channel Analog Front End

Reference Designs

MAXREFDES4
MAXREFDES4
This 16-bit high-accuracy industrial analog input design accepts a 4–20mA current loop or a 0.2V to 4.096V voltage signal as input and provides a digital SPI output. The data path and power is fully isolated.
MAXREFDES4 (Campbell) Circuits from the lab

16-Bit High-Accuracy 4-20mA Input Isolated Analog Front End (AFE)

View Detailed Reference Design

Features and Benefits

  • High accuracy
  • 4–20mA current loop input
  • 0.2V to 4.096V input range
  • Isolated power and data
  • Small printed circuit board (PCB) area
  • Device drivers
  • Example C source code
  • Pmod™-compatible form factor
maxrefdes5fig00
maxrefdes5fig00
maxrefdes5fig01
Santa Fe (MAXREFDES5) Circuits from the lab

16-Bit High Accuracy Multi-Input Isolated Analog Front End (AFE)

View Detailed Reference Design

Features and Benefits

  • High accuracy
  • ±10V, 0 to 10V, and 4–20mA Inputs
  • Isolated power and data
  • Small printed circuit board (PCB) area
  • Device drivers
  • Example C source code
  • Pmod™-compatible form factor

MAXREFDES11 - Block Diagram
MAXREFDES11 - Block Diagram
MAXREFDES11
MAXREFDES11 (Fresno) Circuits from the lab

16-Bit High-Accuracy 0 to 10V Input Isolated Analog Front End (AFE)

View Detailed Reference Design

Features and Benefits

  • High accuracy
  • 0 to 10V input range
  • Isolated power and data
  • Small printed circuit board (PCB) area
  • Device drivers
  • Example C source code
  • Pmod™-compatible form factor
MAXREFDES8 - Design Block Diagram
MAXREFDES8 - Design Block Diagram
MAXREFDES8
MAXREFDES8 (Riverside) Circuits from the lab

3.3V Input, 12V (15V) Output Isolated Power Supply

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Features and Benefits

Features

  • Isolated power
  • 12V (15V) output
  • Small printed circuit board (PCB) area
  • Pmod™-compatible form factor

Applications

  • Industrial sensors
  • Process control
  • Industrial automation
  • Medical
MAXREFDES4 (Campbell)
16-Bit High-Accuracy 4-20mA Input Isolated Analog Front End (AFE)
MAXREFDES4
This 16-bit high-accuracy industrial analog input design accepts a 4–20mA current loop or a 0.2V to 4.096V voltage signal as input and provides a digital SPI output. The data path and power is fully isolated.
Santa Fe (MAXREFDES5)
16-Bit High Accuracy Multi-Input Isolated Analog Front End (AFE)
maxrefdes5fig00
maxrefdes5fig01
Lakewood (MAXREFDES7)
3.3V Input, ±12V (±15V) Output Isolated Power Supply
MAXREFDES7
MAXREFDES7 Design Block Diagram
MAXREFDES11 (Fresno)
16-Bit High-Accuracy 0 to 10V Input Isolated Analog Front End (AFE)
MAXREFDES11 - Block Diagram
MAXREFDES11
MAXREFDES8 (Riverside)
3.3V Input, 12V (15V) Output Isolated Power Supply
MAXREFDES8 - Design Block Diagram
MAXREFDES8

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