System Board 6851

MAXREFDES1126: 0.72V/20A Supply for Xilinx® Ultrascale+ FPGAs

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Input Type VIN (MIN)
Isolated/Non-Isolated Topology
DC 11.4 12.6 20 Single 0.72 14.4 Non-Isolated Synchronous Buck

The MAXREDES1126 provides the internal core voltage (VCCINT) for Xilinx Ultrascale+ FPGAs. This reference design targets FPGAs with a -2L speed grade that require 0.72V for VCCINT from a 12V intermediary bus. The converter supports a maximum load of 20A at a 400kHz switching frequency. The MAXREFDES1126 is centered around the MAX20743 step-down regulator, which is configured for standalone operation. However, the PMBus interface allows for monitoring and control of various converter parameters. All circuitry for the PMBus interface is provided and the MAXPOWERTOOL002# can be used to communicate with the MAXREFDES1126.

The MAXREFDES1126 uses the MAX20743 synchronous step-down regulator. The internal FETs and control loop compensation allow for a compact design with minimal external resources. Additionally, the differential sense lines allow for accurate sensing of the CPU core voltage when located remotely from the MAX20743 IC. The loop gain is selectable to allow design flexibility between stability and output capacitance. A programmable soft-start limits inrush currents during startup. The MAX20743 also offers protections such as input UVLO, output overvoltage/ undervoltage alerts, output overvoltage protection, over-temperature, and current limiting. Moreover, the PMBus interface allows additional parameters to be monitored such as input voltage, output voltage, output current, and temperature. For a full list of PMBus commands, see application note 6042, “PMBus Protocols for Controlling and Monitoring the MAX20743/MAX20730 Switching Regulators

Key Features

  • PMBus Interface
  • Soft-Start
  • Protections
    • Output under/over-voltage alert
    • Current limit and short-circuit protection
    • Over-temperature protection
MAXREFDES1126 Board Enlarge+

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Designed, Built, Tested

The MAXREFDES1126 documentation describes the operation, design, and test results of a synchronous buck converter using the MAX20743 regulator.

Design Resources


Integrated, Step-Down Switching Regulator with PMBus

  • High-Power Density and Low Component Count
  • Optimized Component Performance and Efficiency with Reduced Design-In Time
  • Increased Power-Supply Reliability with System and IC Self-Protection Features

High-Voltage, Low-Power Linear Regulators for Notebook Computers

  • 4V to 28V Input Range
  • 8µA (max) Quiescent Supply Current
  • <1µA Shutdown Supply Current