Intersil adds new 3.3-VRS-485/422 transceivers to LINEARLINK family

EDP Weekly's IT Monitor, Oct 20, 2003

Intersil Corporation (Nasdaq:ISIL), a designer and manufacturer of high performance analog solutions, recently announced two new LINEARLINK RS-485/422 serial data transceivers designed for 3.3-V applications. The ISL83483 and ISL83485 operate from a wide /-10% voltage range of 3 to 3.6 V, which relaxes supply requirements and reduces costs. Many competing products require a more costly /-5% supply tolerance. Applications for these data transceivers include, but are not limited to, factory automation, security networks and building environmental control.

Both the ISL83483 and ISL83485 are half-duplex transceivers whose receive (Rx) and transmit (Tx) functions are multiplexed, reducing pin count and package size with only 8-leads. Rx inputs feature a fail-safe-if-open design, which ensures a logic high Rx output if Rx inputs are floating. A "lock-out" feature keeps the Rx output disabled, when exiting shutdown, until the Rx has determined what state it should go to. This prevents the Rx output from accidentally generating an interrupt while the Rx wakes up. Although these are 3.3-V devices, their logic inputs can be driven with 5-V logic levels in mixed voltage systems.

Driver outputs are short circuit protected, even for voltages exceeding the power supply voltage. Additionally, on-chip thermal shutdown circuitry disables the Tx outputs to prevent damage if power dissipation becomes excessive. Each device supports a combination of up to 32 drivers and receivers on a single bus enabling bi-directional communications over a single twisted-pair cable. In addition, both devices have an automatic low-power shutdown feature in which the device draws only 15 nA (typical).

The ISL83483 is slew-rate limited for error free data transmission in applications where the data rate is less than 250 kbps, typically used for long runs. Slew-rate limiting reduces EMI and minimizes reflections from improperly terminated transmission lines, or unterminated stubs in multi-drop and multipoint applications.

The ISL83485 can operate up to 10 Mbps for high-speed applications. These transceivers are built using the Intersil BiCMOS process and meet both the RS-485 and RS-422 standards for balanced (differential) communication. Balanced data-transmission schemes offer robust noise immunity for data communications over long distances.

The typical use for RS-485 is a single PC connected to several addressable devices that share the same cable. RS-422 is similar to RS-485 except that only one driver and up to ten receivers are allowed on the bus. The single driver limitation requires two twisted pairs for bi-directional communications.

The ISL83483 and ISL83485 are available now. Suggested resale pricing for 100-to 999-unit quantities is $1.21 each for the ISL83483IB (SOIC package) and ISL83483IP (PDIP package) and $1.05 each for the ISL83485IB (SOIC package) and ISL83485IP (PDIP package). Both are available on tape and reel.