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Synchronizable, High-Frequency Current- and Voltage-Mode PWM Controllers for Isolated Supplies

Versatile, High-Frequency PWM Controllers Reduce Isolated DC-DC Converter Size and Cost

Product Details

Key Features

Simplified Block Diagram

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Key Features

  • 200kHz to 1MHz Adjustable Switching Frequency
  • Synchronization to External Clock
  • Programmable, Constant Maximum Volt-Second Simplifies Transformer Design
  • Programmable Hiccup/Skip Cycles or Latch-Mode Protection
  • Clean Startups with High-Capacitance Loads
  • Programmable Under/Overvoltage Protection
  • Current-Mode, Adjustable Slope Compensation (MAX8540)
  • Voltage-Mode, Adjustable Ramp Magnitude (MAX8541)
  • 10mA, 5V Regulator
  • 75mV to 1.25mV Adjustable Current Limit Reduces External Components
  • Internal Gate Driver for Low-Power Applications
  • External Gate Driver for High-Power Applications

Applications/Uses

  • Cell Phone Base Stations
  • High-Performance Offline AC/DC Converters
  • Isolated DC-to-DC Modules (Bricks)
  • Telecom and Network Systems

Description

The MAX8540/MAX8541 pulse-width-modulated (PWM) controllers for forward/flyback isolated DC-to-DC converters provide maximum flexibility to power-supply designers and reduce external component count. These controllers allow common PC board layout for current-mode (MAX8540) and voltage-mode (MAX8541) designs.

Both controllers feature adjustable switching frequency and external synchronization from 200kHz to 1MHz. Active-high and active-low enable, undervoltage protection (UVP), and overvoltage protection (OVP) reduce external component count.

Maximum duty cycle is adjustable, and the feed-forward function scales the maximum duty cycle with input voltage to limit the maximum volt-seconds applied to the transformer primary. The MAX8540 allows the user to select the value of slope compensation to further optimize magnetics design. The MAX8541 features user-adjustable ramp magnitude for the PWM comparator.

A cycle-by-cycle current-limit function controls the peak primary current during overload and short circuit. Both controllers can be set to latch off or to hiccup when a short circuit is detected. The number of current-limited cycles to initiate the hiccup mode and number of cycles skipped are user selectable to allow startup with high-capacitance loads and protect the converter against sustained short circuits.

The MAX8540/MAX8541 feature 9Ω internal gate drivers for low-power applications and are compatible with external gate drivers for high-power applications. Both devices are available in the space-saving 16-pin QSOP package.

The MAX8541 EV kit evaluates the MAX8540 and the MAX8541 to speed designs. Design examples are also available in application notes: 50W Voltage-Mode Forward Converter Design with the MAX8541 and 50W Current-Mode Forward Converter Design with the MAX8540.

Simplified Block Diagram

MAX8540, MAX8541: Typical Operating Circuit MAX8540, MAX8541: Typical Operating Circuit Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .