This article features the MAX3100 universal asynchronous receiver transmitter with an isolated serial interface, the first UART particularly perfected for small microcontroller-based systems. With the use of an SPI™/MICROWIRE™ interface for contact with the host microcontroller (µC), the MAX3100 comes in a compressed 16-pin QSOP. The asynchronous I/O is appropriate for use in RS-232, RS-485, opto isolated data links and IR. IR-link interaction is easy with the MAX3100's infrared data association (IrDA) timing mode.

The MAX3100 contain a crystal oscillator and a baud-rate maker with software-programmable separator ratios for all ordinary baud rates from 300 baud to 230k baud. A software or hardware call upon power cut and lowers quiescent current to 10µA, at the same time allowing the MAX3100 to sense receiver activity.

An buffer that is 8-word-deep FIFO, reduces processor overhead. This device adds a flexible break off with four mask able sources, including address detection on 9-bit networks. Two hardware link control lines are included, one input and output. It is available in 14-pin plastic DIP and small, 16-pin QSOP with extended temperature ranges and in commercial packages.

Its applications include Handheld Instruments like PDAs and Palmtops, Isolated RS-232/RS-485: Directly Drives Optocouplers, Small Networks in HVAC or Building Control, UART in SPI Systems, Low-Cost IR Data Links for Computers/Peripherals and Intelligent Instruments.

Its key features are Small TQFN and QSOP Available Packages, SPI/Microwire-Compatible µC Interface, +2.7V to +5.5V Supply Voltage in Operating Mode, Schmitt-Trigger Inputs for Opto-Couplers, 10µA in Shutdown with Receive Interrupt, TX and RTS Outputs Sink 25mA for Opto-Couplers, Lowest Power 150µA Operating Current at 3.3V, IrDA SIR Timing Compatible, 8-Word FIFO Minimizes Processor Overhead at High Data Rates, Up to 230k Baud with a 3.6864MHz Crystal, 9-Bit Address-Recognition Interrupt and Receive Activity Interrupt in Shutdown.

The MAX3100 Schmitt-trigger inputs are directly driven by opto-coupler outputs. The MAX845 linear regulator and transformer driver provide the isolated power. An important feature of this function is that the opto-coupler’s skew neglect the asynchronous serial output’s timing.

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