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Tiny transceivers offer up to 20Mbps data rates

Posted: 27 Feb 2007 ?? ?Print Version ?Bookmark and Share

Keywords:transceiver? ESD protection? receiver? Intersil? transmitter?

ISL315XE family of transceivers from Intersil

Intersil Corp. has introduced the ISL315XE family of 5V RS-485/RS-422 transceivers. This six-member family promises to save 50 percent to 70 percent of valuable board space with tiny 8- and 10-lead MSOP package options and deliver data transmission rates up to 20Mbps.

According to the company, the ISL315XE family provides maximum reliability of exposed transmitter and receiver RS-485 bus pins with IEC61000 ESD protection that allows customers to develop the most rugged systems possible for harsh industrial environments. The family's higher output voltage (2.4V min.) is 60 percent larger than the 1.5V required by the RS-485 standard, providing the advantage of nearly 1V greater noise immunity and the ability to drive longer cable lengths, resulting in a more robust serial communication system.

System reliability
"The unique combination of high ESD protection and increased output drive gives designers of high-performance industrial applications a new level of system reliability," said Randy Pitts, marketing manager of Intersil's interface products group. "Combining the tiny MSOP package option will enable smaller PCB designs or additional features in the same area."

The ISL315XE family is made up of BiCMOS, IEC61000 ESD-protected, 5V-powered single transceivers that meet both the RS-485 and RS-422 standards for balanced communication. Each driver output and receiver input is protected against 16.5kV ESD strikes without latch-up.

The ISL315XE transmitters deliver high differential output voltages (2.4V min) into the RS-485 required 54-ohm load, for better noise immunity or to allow up to eight 120-ohm terminations in "star" or other non-standard bus topologies. These transmitters deliver RS-485 compliant levels (1.5V) even with eight termination resistors. Unlike competing devices that require up to 15mA quiescent supply currents, the ISL315XE family requires only 800?A (max), the company said. Power consumption is further reduced via a low-power shutdown feature that reduces Icc to 70nA when the driver and receiver are both disabled.

These devices have very low bus currents, so they provide a true 1/8 unit load to the RS-485 bus. This allows up to 256 transceivers on the network without violating the RS-485 specification's 32-unit load maximum and without using repeaters.

'Full fail-safe'
Receiver (Rx) inputs feature a "full fail-safe" design, which ensures a logic high Rx output if Rx inputs are floating, shorted, or on a terminated but undriven bus. Rx outputs feature high drive levelstypically 28mA at VOL = 1Vto ease the design of optocoupled isolated interfaces.

The ISL3150E, ISL3152E, ISL3153E and ISL3155E use slew-rate-limited drivers that reduce EMI and minimize reflections from improperly terminated transmission lines, or unterminated stubs in multidrop and multipoint applications. The ISL3156 and ISL3158 are rated up to 20Mbps data rate for high-speed applications.

Hot plug circuitry ensures that the Tx and Rx outputs remain in a high impedance state until the power supply has stabilized. The Tx outputs have full short circuit protection.

The ISL3150E, ISL3153E, ISL3156E are configured for full duplex applications. The half duplex versions multiplex the Rx inputs and Tx outputs to allow transceivers with output disable functions in 8-lead packages.

The ISL315XE family is available now in 8-lead MSOP packages, 8-lead SOIC packages, 10-lead MSOP packages and 14-lead SOIC packages with prices starting at $1.26 in 1,000-unit quantities.

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