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connectivityZONE Products for the week of July 6, 2009
Intersil Says…
New, Flexible Low-Power, Low-Leakage Quad RS-422 Transmitters Deliver Maximum ESD Protection in Industry’s Smallest Packages
ISL32179E, ISL32272E/74E Feature Extended Voltage and Temperature Ranges for Motor and Process Control, Telecommunications, Factory Automation Applications
Intersil Corporation has developed a new series of small-footprint quad 16.5kV ESD-protected RS-422 transmitters. These innovative new devices feature wide supply-voltage operating ranges for motor control applications, process control networks, telecommunications products and factory automation systems.
The new ISL32179E, ISL32272E and ISL32274E withstand ESD during assembly and while in use, featuring +/- 16.5 kV ESD protection that meets HBM and IEC61000-4-2 standards on transmitter outputs. All of the new transmitters also feature power-saving low-output leakage currents, at just ± 20μA. Designed to operate from either 3.3V or 5V and at temperatures between -40 to 125 degrees C, the new transmitters can replace existing RS-422 transmitters that are restricted to 5V supply voltages or that operate in limited temperature ranges.
The ISL32179E, ISL32272E and ISL32274E are superior choices for designs using the RS-422 communication interface, providing maximum protection from the harshest ESD events during assembly and use. Data rates reach 32 Megabits/second, and quiescent current is a low 0.8 mA, maximum. Slew rate-limited versions are also offered, so low data rate applications can minimize EMI and transmission line reflections. Shutdown supply current is as low as 60 μA on the QFN package versions. Driver (Tx) outputs are tri-statable, and incorporate a hot-plug feature to keep them disabled during power-up and power-down.
Industry-standard versions are available in TSSOP or widely used NSOIC packages, while the ISL32179E is offered in tiny 4mm x 4mm QFN packages that are 50 percent smaller than the TSSOPs, providing significant board-space savings. The ISL32179E also features data-rate and enable options, offering maximum design versatility. Multiple enable pins allow the user to choose active high or low group enables (EN or EN#), paired-enables (EN12 and EN34) or individual channel enables, available on the ISL32179E, and speed select pins allow the user to select data rates from 460kbps to 32Mbps, also available only on the ISL32179E. The ultra-small QFN package incorporates a VL pin to adjust the logic-pin input thresholds, eliminating the need for extended voltage level translator ICs in most designs.
EN-Genius Says…
I was a bit surprised when I first saw Intersil’s announcement of its extra-rugged RS-422 devices. Why on Earth would they invest all that money to bring new parts to an extremely mature market with so many well-proven parts already available? Intersil says that their lead customer’s requirements for a new motor controller drove them to develop these devices which offer higher speed (32 Mbit/s) and higher temperature operation (125ºC). The application’s tight space constraints (the controller is mounted inside the motor) also drove Intersil to offer the new parts with an optional QFN package in addition to their already-tiny 16 lead TSSOP. Their QFN version has several features that add greatly to the transmitter’s flexibility including an integrated level shifter, user selectable speed options, and enable functions that allow group, paired, or individual channel selection.
It still puzzled me however, why there would be so much demand for a 40+-year-old technology when USB, Ethernet, and interface technologies offer much better speed and flexibility? A quick inquiry to Intersil revealed that they are still doing a thriving business in RS-422/485 products because many of their customers still need its ability to operate in noisy/harsh environments that would quickly put a more modern technology out of commission. In fact, RS-422’s differential drive scheme allows it to operate quite nicely even when the common mode range on the bus pins exceeds the supply voltage. It can also reach much longer distances than USB (up to 4000 ft.) and, unlike USB, supports point-to-multi-point connections.
Since these capabilities give RS-422 such significant advantages in challenging environments, I’m sure that the extra electrical protection and thermal margins offered by these new devices will make them a winner in factory automation and process control equipment and many industrial other applications. That’s why I was not completely surprised to learn that the majority of Intersil’s design wins in RS-422/485 are in new system designs. They report finding new applications for these parts on a regular basis, including security systems, CCTV, theft detection, power inverters, POS, DVR, robotics, e-meters, air conditioning systems, and electronic voting machines.
The ISL32272E and ISL32274E are in production in TSSOP-16 and SOIC-16 with prices starting at $1.60 in 1000-piece lots. The ISL32179E is in QFN-24, with prices starting at $1.73 in 1000-piece lots.
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