Maxim Integrated Products introduced the MAX3130/MAX3131 Transceivers -- the first devices to integrate an IrDA and RS-232 interface for portable and low-power applications. Both devices save valuable board space by integrating an infrared (IR) transceiver, IR encoder/decoder (ENDEC), charge pump, and RS-232 interface into one surface-mount package. The IR transceiver is IrDA 1.2-compatible, supporting data rates of 2.4kbps to 115kbps. The RS-232 interface includes two drivers and two receivers that support data rates up to 120kbps.

Both devices consume 370ưA in normal operation and only 1ưA while in shutdown (with RS-232 receivers active). Their low-dropout transmitters and proprietary, high-efficiency, dual-charge-pump power supply combine to deliver true RS-232 and IrDA performance from a single supply voltage of +3.0V to +5.5V. The IR transmitter includes a high-power LED driver capable of delivering 200mA; the IR receiver includes a high-gain, low-noise PIN-diode amplifier that rejects 200ưA of ambient DC current. The internal ENDEC stretches/compresses signals passing between the IR transceiver and the UART to enable communication with non-IrDA UARTs.

The MAX3130 is optimized for applications using one UART for both IR and RS-232 communications -- its IR transmitter input and receiver output are multiplexed with one RS-232 transmitter input and receiver output, respectively. The MAX3131's IR and RS-232 transceivers have separate data lines for the input and output.

These parts are unique today. That said, is there a market for them? Yes, I think there is. I do not personally think much for the long-term future of the IrDA standards; they are neat, they work, they are fascinating. but in the future the demands for higher and higher communications speeds are probably not going to be met in this way and the 1394 standards are probably the next wave of the future. Given that, combining any IrDA communications device with another standard, a wired standard, is probably a very good way to go.

With these two Maxim parts you effectively have two RS-232 channels and one IrDA channel with the complication that the data is the same in the MAX3130 for one of the RS-232 channels and the IrDA channel. That multiplexing may well save some external connections for some applications. All the right things are included to get the RS-232 data right in amplitude and slew rate for a supply voltage of only +3 V, and the receiver and transmit circuits are ready to go on the IrDA side of the part, with just a transmit LED and a receive photodiode needed.

The shut down current of only 1ưA is really impressive when you are reminded that the RS-232 receivers are still powered, and drawing only a little more than a third of a milliamp, fully operational, makes these parts absolutely ideal for portable devices. I can quite see this as a rapidly adopted pair of parts for PDAs and palm-top computers of all kinds giving data transfers most of us using 56K modems will feel is quite fast. (The Maxim use of "kbps" floors me; IEEE standards would expect Kbit/s, differentiating a real 1000 from a computer's idea of 1000, and differentiating bits from bytes.)

Both the MAX3130 and 3131 are in production in 28-pin SSOP and are priced at $4.53 in 1000-piece lots.