Transceivers aren't too fussy about supply

Two new full-duplex RS485/422 serial data transceivers operate from a nominal 3.3V supply over a wide +/-10% voltage range of +3 to +3.6V, which relaxes supply requirements and reduces costs.

The Linearlink ISL83488 and ISL83490 are full-duplex transceivers that operate from a nominal 3.3V supply over a wide +/-10% voltage range of +3 to +3.6V, which relaxes supply requirements and reduces costs.

These new ICs satisfy both low- and high-speed (250Kbit/s and 10Mbit/s) serial communications needs as used in, but not limited to, factory automation, security networks and building environmental control.

The ISL83488 and ISL83490 are both configured for full-duplex operation with separate Rx input and Tx output pins.

These devices are well suited for RS422 applications because they don't typically require Tx and Rx enable functions and both driver and receiver are independently accessible.

By eliminating the enable functions, full duplex functionality is realised in a small 8-lead package.

These 3.3V devices can be driven with 5V logic levels in mixed voltage systems.

Rx inputs feature a fail-safe-if-open design, which ensures a logic high Rx output if Rx inputs are floating.

This prevents the Rx output from chattering, and accidentally generating interrupts, if the receiver becomes disconnected from the bus.

Driver outputs are short circuit protected.

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 large four-wire full duplex systems.

The ISL83488 is slew-rate limited for error free data transmission in applications where the datarate is less than 250Kbit/s, typically used for long runs.

Slew-rate limiting reduces EMI and minimises reflections from improperly terminated transmission lines, or unterminated stubs in multidrop and multipoint applications.

The ISL83490 can operate up to 10Mbit/s for high-speed applications.

These transceivers are built using the Intersil BiCMOS process and meet both the RS485 and RS422 standards for balanced (differential) communication.

Balanced data-transmission schemes offer robust noise immunity for data communications over long distances.

The typical use for RS485 is a single PC connected to several addressable devices that share the same cable.

RS422 is similar to RS485 except that only one driver and up to ten receivers are allowed on the bus.

The single driver limitation requires two twisted pairs for bidirectional communications.

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