Radiation hardened multiplexers

Paul Boughton

Intersil Corporation’s ISL71840SEH and ISL71841SEH radiation hardened (rad hard) multiplexers are claimed to 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.

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);

* EL/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 analogue signal chain with superior radiation tolerant performance.