Rad-hard multiplexers for space flight data acquisition systems

July 14, 2015 // By Graham Prophet
Intersil’s ISL71840/41SEH multiplexers claims best-available ESD protection; these radiation hardened (rad hard) multiplexers also claim highest signal chain accuracy and timing performance.

The ISL71840SEH 30V 16-channel multiplexer is a drop-in replacement for Intersil’s HS9-1840ARH, which the company says has been aboard many satellite and space exploration missions, including NASA’s recent Orion spacecraft flight test. For applications with form factor constraints, the ISL71841SEH 30V 32-channel multiplexer offers high performance and 41% reduced board space compared with an ISL71840SEH two-chip solution.

The ISL71840SEH and ISL71841SEH rad hard multiplexers deliver performance in the most demanding environments by exploiting Intersil’s proprietary silicon-on-insulator process, which provides single event latch-up (SEL) robustness in heavy ion environments. The enhanced 8-kV ESD protection feature of these devices eliminates the need for costly external protection diodes on the input pins. And their reduced RON of 500 Ohms at ±5V and propagation delays of less than 800 nsec increase the overall performance and accuracy of telemetry signals processed and multiplexed into an analogue-to-digital converter (ADC) input.

The ISL71840SEH and ISL71841SEH offer over-voltage protection on a per-switch basis to maintain the continuous processing of telemetry test points. If any input channel experiences an over-voltage condition, the remaining channels continue sending data to the ADC. Both multiplexers provide a “cold spare” redundant capability, allowing the connection of 2-3 additional un-powered multiplexers to a common data bus. This is an especially important feature for mission-critical space flights lasting up to 20 years. If required for any reason, a redundant multiplexer is immediately activated. Both multiplexers provide a wide supply range with split-rail operation from ±10.8V to 16.5V and an absolute maximum of ±20V, providing designers with ample de-rating headroom.

The ISL71840SEH 16-channel multiplexer is available in a 18.8 x 14 mm, 28-lead ceramic flatpack package, and the ISL71841SEH 32-channel multiplexer comes in a 14 x 14 mm, 48-lead ceramic quad flatpack. Both multiplexers are also available in die form. Two evaluation boards are available to evaluate device features and performance: 16-channel ISL71840SEHEVAL1Z and 32-channel ISL71841SEHEVAL1Z.

Intersil; www.intersil.com/products/isl71840seh

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