Maxim introduces the MAX3421E, an USB host and peripheral controller with an SPI interface. This device integrates digital logic and analog circuitry to implement a full-speed (12Mbps) USB host or peripheral control compliant to the USB specification 2.0. The MAX3421E makes it possible to add USB host capabilities to any microprocessor. Embedded systems with USB host capability can interface to inexpensive USB keyboards and mice, upload firmware from USB FLASH drives, or take advantage of the capabilities of the large number of USB devices available. The MAX3421E can also operate in the USB peripheral mode, and is software compatible with the Company's MAX3420E USB peripheral controller with SPI interface. The device integrates a ±15kV ESD-protected USB transceiver, an USB serial interface engine (SIE), double-buffered endpoint memories, an SPI slave interface, and software-controlled USB pullup and pulldown resistors. The integrated USB transceiver supports full-speed (12Mbps) and low-speed (1.5Mbps) USB in the host mode and full-speed USB as a peripheral.

The SIE handles low-level USB protocol details such as automatic NAK until ready, bit stuffing, CRC generation/checking, bus retries, automatic SOF/keep-alive generation, and USB hub support in the host mode. The MAX3421E operates using a register set accessed by the SPI interface, which operates up to 26MHz. Any SPI master (microprocessor, ASIC, DSP, etc.) can add USB functionality using the simple 3- or 4-wire interface. A programmable interrupt output can be used to reduce or eliminate microprocessor polling. Integrated logic-level translators allow the SPI interface to operate at a system voltage between 1.4V and 3.6V. Additionally, eight general-purpose inputs and outputs allow any microprocessor that uses I/O pins to implement the SPI interface to reclaim those pins and gain additional ones. For time-critical operations such as OTG signaling, a second interrupt pin can be dedicated to the eight general-purpose inputs, each of which can cause an interrupt. The MAX3421E operates over the extended temperature range (-40 degrees Celsius to +85 degrees Celsius). This device is available in 5mm x 5mm, 32-pin TQFP and 5mm x 5mm, 32-pin TQFN packages. Prices start at $3.47 (1000-up, FOB USA).