Dual Serial UART with 128-Word FIFOs

Industry's Most Advanced Dual SPI/I²C UART Increases System Flexibility

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The MAX3109 advanced dual universal asynchronous receiver-transmitter (UART) has 128 words of receive and transmit first-in/first-out (FIFO) and a high-speed SPI or I²C controller interface. The 2x and 4x rate modes allow a maximum of 24Mbps data rates. A phase-locked loop (PLL) and the fractional baud-rate generators allow a high degree of flexibility in baud-rate programming and reference clock selection.

Independent logic-level translation on the transceiver and controller interfaces allows ease of interfacing to microcontrollers, FPGAs, and transceivers that are powered by differing supply voltages. Automatic hardware and software flow control with selectable FIFO interrupt triggering offloads low-level activity from the host controller. Automatic half-duplex transceiver control with programmable setup and hold times allow the MAX3109 to be used in high-speed applications such as PROFIBUS-DP. The 128-word FIFOs have advanced FIFO control, reducing host processor data flow management.

The MAX3109 is available in a 32-pin TQFN (5mm x 5mm) package, and is specified over the -40°C to +85°C extended temperature range.
MAX3109: Functional Diagram MAX3109: Functional Diagram Enlarge+

Key Features

  • Bridges an SPI/MICROWIRE or I2C Microprocessor Bus to an Asynchronous Interface Such as RS-485, RS-232, or IrDASM
    • SIR- and MIR-Compliant IrDA Encoder/Decoder
    • Line Noise Indication Ensures Data Link Integrity
  • Deep, 128-Word Buffer and Automated Control Features Help Offload Activity on the Microcontroller
    • Automatic Active-Low RTS_ and Actie-Low CTS_ Flow Control
    • Automatic XON/XOFF Software Flow Control
    • 9-Bit Multidrop-Mode Data Filtering
      • Special Character Detection
      • GPIO-Based Character Detection
      • Two Timers Routed to GPIOs
      • 8 Flexible GPIOs with 20mA Drive Capability
  • Saves Board Space
    • TQFN (5mm x 5mm) Package
    • Dual UART in a Single Package
  • Fast Data Rates Allow Maximum System Flexibility Across Interface Standards
    • 24Mbps (max) Data Rate
    • High-Resolution Programmable Baud-Rate
    • SPI Up to 26MHz Clock Rate
    • Fast Mode Plus I2C Up to 1MHz
  • Integrated Internal Oscillator Eliminates the Need for an External Oscillator and Reduces the BOM Cost
    • Integrated PLL and Divider
  • Power Management Control Features Minimize Power Consumption for Portable Applications
    • 1.71V to 3.6V Supply Range
    • Shutdown and Autosleep Modes
      • 1µA Shutdown Current
  • Logic-Level Translation on the Controller and Transceiver Interfaces Ensure System Compatibility
  • Register Compatible with MAX3107, MAX3108, and MAX148301


  • Automotive Infotainment Systems
  • Handheld Devices
  • HVAC or Building Control
  • Medical Systems
  • Point-of-Sales Systems
  • Power Meters
  • Programmable Logic Controllers (PLCs)
Part NumberµP I/FChannelsICC
Package/PinsOper. Temp.
typSee Notes
MAX3109 SPI and I2C Compatible20.51.7 to 3.6
-40 to +85$6.01 @1k
See All SPI/Microwire-Compatible UARTs (6)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Technical Documents

App Note 5304 Interfacing to the MAX3108 UART
App Note 4938 Differences Between Maxim's Advanced UART Devices

Quality and Environmental Data

Product Reliability Reports: MAX3109.pdf 
Lead-Free Package Tin (Sn) Whisker Reports
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

Quality Management System >
Environmental Management System >


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