Radiation Hardened Multiplexers for Space Flight Data Acquisition Systems

Intersil ISL71841SEHIntersil Corporation introduced the ISL71840SEH and ISL71841SEH, new radiation hardened (rad hard) multiplexers that offer best-in-class electrostatic discharge (ESD) protection, and the industry’s highest signal chain accuracy and timing performance. The ISL71840SEH 30V 16-channel multiplexer is a drop-in replacement for Intersil’s widely adopted HS9-1840ARH, which has been aboard nearly every satellite and space exploration mission, including NASA’s recent Orion spacecraft flight test. For applications with form factor constraints, the new 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 ultra-high performance in the most demanding environments by leveraging Intersil’s proprietary silicon on insulator process, which provides single event latch-up (SEL) robustness in heavy ion environments. The enhanced 8kV 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 800ns increase the overall performance and accuracy of telemetry signals processed and multiplexed into an analog-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 unpowered 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 plenty of de-rating headroom.

“The ISL71840SEH and ISL71841SEH multiplexers build upon the performance and reliability of the HS9-1840ARH, while providing additional features to support the latest needs of data acquisition systems,” said Philip Chesley, senior vice president of Precision Products at Intersil. “The 16-channel and 32-channel devices are ideally suited to meet the mission assurance needs of next-generation satellites and manned spacecraft for deep space exploration.”

Key Features and Specifications

  • Delivers 8kV human body model (HBM) ESD protection
  • Provides true rail-to-rail operation and features over-voltage protection with shutoff
  • Cold sparing from ground +/-25V and analog over-voltage range from ground +/-35V
  • Off switch leakage of 100nA and low RON of less than 500 Ohms reduces power consumption, and improves signal integrity and total harmonic distortion
  • Triple redundant decoders with a fast response time of <5us drastically improves single event transient (SET) performance
  • Improved off-isolation and crosstalk rejection ensures the output leaks to ground whenever the multiplexer is disabled
  • Adjustable logic threshold control with VREF pin
  • High dose rate (50-300rad(Si)/s) radiation tolerance of 100krad(Si)
  • Low dose rate (0.01rad(Si)/s) radiation tolerance of 50krad(Si)
  • SEL/B immune up to 86MeV.cm2/mg

The ISL71840SEH and ISL71841SEH multiplexers can be combined with the ISL71590SEH rad hard temperature sensor, ISL71090SEH25 voltage reference, and operational amplifiers such as the ISL70444SEH, ISL70244SEH, ISL70417SEH, ISL70218SEH, ISL70227SEH, ISL70419SEH to support a complete analog signal chain with superior radiation tolerant performance.


The ISL71840SEH 16-channel multiplexer is available in a compact 18.8mm x 14mm, 28-lead ceramic flatpack package, and the ISL71841SEH 32-channel multiplexer comes in a 14mm x 14mm, 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.

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