SPI/I2C UART integrates an oscillator to offer fast data rates

Maxim Integrated Products has introduced what the company claims is industry's lowest power, fastest, and smallest serial UART to communicate over an SPI/I2C interface.

The MAX3107 has low power consumption which will extend battery life in portable applications. The device's fast data rates (24Mbps) and deep FIFO (128 words) allow additional buffering and thus relieve demand on the system's microcontroller. The MAX3107 is packaged in a space-saving, 24 pin (3.5mm x 3.5mm) TQFN, which is 24 percent smaller than other serial UARTs in the market today. The MAX3107 UART also offers an industry first, an integrated oscillator that reduces BOM cost by an average of 20 percent. The MAX3107 is ideally suited for industrial field buses that require high-speed PROFIBUS DP communication protocols, and for low-power handheld consumer MIDs (mobile Internet devices).

For short, local-link applications as in a mobile phone, the UART can serve as the buffer between the system's applications processor (a microcontroller) and modules like Bluetooth, satellite radio, GPS, or 3G modems. Higher data rates are now used for communication with Bluetooth (up to 3 Mbps) and 3G modems (up to 20 Mbps). These data rates typically cannot be supported by a microcontroller's embedded UART. To address these communication demands, designers traditionally used an external UART that supported these speeds. The additional UART also helps to offload (buffer) the microprocessor's activities.

The MAX3107 meets this high-speed challenge by providing the fast data rates required by today's communication devices. The device claims best-in-class data rates (up to 24Mbps) thereby making it ideal for 3G modem applications. Additionally, the MAX3107's integrated oscillator reduces the need for external clocking.

The MAX3107 UART interfaces an SPI or I2C synchronous serial microprocessor bus to asynchronous, serial data-communication ports like RS-485, RS-232, PROFIBUS, or IrDA. The PROFIBUS DP standard requires fast data-rate communication (up to 12Mbps) which most embedded UARTs on today's microcontrollers cannot support. The MAX3107's 24Mbps performance is ideal for these communication protocols.

The MAX3107 improves SPI/I2C data throughput. The UART's receiver and the transmitter each have a 128-word-deep FIFO (vs. the competition's 64), which reduces the intervals that the host processor must dedicate for high-speed, high-volume data transfer.

As the data rates of the asynchronous Rx/Tx interfaces increase and approach the maximum limits of the host controller's SPI/I2C data rates, a UART's management and flow control can consume a significant portion of the host's activity. By increasing the FIFO size in the MAX3107, the host is interrupted less often, thus providing more efficient SPI/I2C-based DMA block data transfer to/from the FIFOs.

The MAX3107's PLL, clock divider, prescaler, and fractional baud-rate generator allow the ultimate flexibility in high-resolution baud-rate programming. The baud rate is no longer dependent on the frequency of the reference clock, but can be independently set to meet system needs.

In addition, low-level activity is also offloaded from the host controller to the UART because of the MAX3107's automatic hardware and software flow control with selectable FIFO interrupt triggering.

Automatic half-duplex transceiver control with programmable setup and hold times allows the MAX3107 to be used in high-speed applications like PROFIBUS DP.

The MAX3107 uses multiple operational modes to lower power consumption. The sleep mode turns off all UART-related on-chip clocking, while the shutdown mode turns the chip off completely. These modes reduce the supply currents to a trickle during periods of nonoperation. In AutoSleep mode, the MAX3107 automatically enters sleep mode after a period of no activity on its IO pins. The device automatically wakes up when activity is detected on any input pin.

During both standby modes of operation, the UART stops transmitting and receiving and disables specific functionality to reduce power consumption. These many power-saving modes reduce battery drain and extend battery life to make the MAX3107 the ideal ultra-low-power UART for mobile applications.

The MAX3107 operates from +2.35 V to +3.6 V and is fully specified over the industrial -40 to +85 degrees Celsius temperature range. It comes packaged in a 24-pin (3.5 mm x 3.5 mm) TQFN and is priced at $3.25 (1000-up, FOB, USA). An EV (evaluation) kit is available to speed designs.



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