Space-rated analog ICs are increasingly standard catalog items

It wasn’t that long ago that space-rated components were special in every possible sense. They had to be ordered via a different process well in advance of fabrication, manufactured to order, undergo the additional tests to qualify them, and more.

Most of the attention of spaced-rated component vendors was on larger ICs such as processors, FPGAs, communication components, and similar. Basic analog ICs were not on that list of potentially available space-rated devices.

Yet designers know that a viable functioning system requires more than those larger ICs. It also takes the small-to-medium analog ICs serving in mundane yet vital roles such as basic current amplifiers, level sifting, and temperature sensing to complete a design.

But times have changed. The listing of these basic-function analog ICs as standard items means that design uncertainty is reduced along with time to project completion and cost. It’s part of the mainstreaming of space satellites, with the proliferation of low-Earth orbit (LEO) and medium-Earth orbit (MEO) vehicles in unit volumes that were unimaginable just a decade or so ago. Both amateur satellite designers (such as CubeSat) and commercial operations are beneficiaries of space-rated standard catalog parts.

One of the key enablers of space-rated components was the 2024 release of QML Class P, a qualification standard for radiation-hardened plastic-encapsulated ICs used in space applications. It extends MIL-PRF-38535 specifications via SAE standard AS6294 to provide a reliable plastic alternative to traditional ceramic packaging.

Engineers designing small satellites for LEO missions with shorter mission durations and lower-cost targets have begun to use commercial-off-the-shelf (COTS) ICs, which receive no special screening from manufacturers to address the hazards of spaceflight. But these are a limited subset of the broader picture in satellite designs.

As evidence of the increase in these space-rated basic-analog ICs, one example comes from Texas Instruments, who introduced three very different ICs with these ratings in the past few months. Radiation-hardened performance for each is spelled out in detail in their respective comprehensive datasheets, including total ionizing dose (TID) and single-event effects (SEE), with the latter for both single event latch-up (SEL) and single event transient (SET) occurrences.

  • INA951-SEP is a current-sense amplifier that can measure voltage drops across shunt resistors over a wide common-mode range from –4 V to 80 V (Figure 1). The negative common-mode voltage allows the device to operate below ground, thus accommodating precise measurement of recirculating currents in half-bridge applications.

Figure 1 The current-sense amplifier is a widely used arrangement; it’s based on measuring the voltage across a known sense resistor. Source: Texas Instruments

  • TRF0108-SP is a radiation-hardness-assured, differential to single-ended (D2S) RF amplifier for near-DC to 12 GHz use (Figure 2).

Figure 2 TRF0108-SP performs the simple yet essential function of translating differential DAC output signals between near-DC and 12 GHz into a single-ended signal compatible with a power amplifier (PA). Source: Texas Instruments

A common application for this device is as a buffer amplifier for an RF DAC that has differential outputs. In many conventional designs, passive baluns are used to interface differential amplifier outputs with single-ended RF DACs. TRF0108-SP replaces these bulky and expensive passive baluns while offering excellent gain and phase imbalance, as well as input and output return loss.

  • Finally, there’s temperature. It’s a rare system of any sort (whether space-related or not) that doesn’t need temperature sensing across multiple points, either for its native functionality or to monitor operating conditions independent of that functionality. That’s where the TMP9R01-SP high-accuracy remote and local temperature sensor has its place (Figure 3).

Figure 3 The TMP9R01-SP high-accuracy temperature sensor reads and digitizes the temperature of its internal sensor as well as up to nine bus-linked remote sensors. Source: Texas Instruments

The device measures remote temperature (–64°C to 191°C range and ±1.5°C maximum error) by forcing a bias current through an external BJT or the integrated diode/junction of an FPGA, ADC, or ASIC, digitizing the resulting ΔVBE and reporting temperature with 0.0625⁰C resolution. An additional on-chip sensor provides local temperature measurement (±2.0⁰C maximum error).

Of course, the push for standard-catalog space-rated ICs is not just from one vendor. Others, such as Microchip Technology, have a long list of such ICs in their catalogs; while many are higher-level components such as processors and FPGAs, a large number are analog and power devices.

“Volume production” has a different meaning for spacecraft

Until the relatively recent proliferation of LEO and MEO satellites, a satellite was individually designed and tested, with no two exactly alike. Certainly, there were cases where subsections were reused in subsequent craft, but each satellite was largely unique.

Interestingly, there is one dramatic exception to this uniqueness dating way back, although it’s a small one. Identical twins Voyager 1 (launched September 5, 1977) and Voyager 2 (August 20, 1977) were built by NASA on an accelerated schedule, as they had a very tight launch window (Figure 4); see Voyager: Seeking Newer Worlds in the Third Great Age of Discovery.

Figure 4 The twin Voyager spacecraft were designed and built on an extremely tight schedule with no room for launch delay, and were optimized for long-term, scientific investigation missions. They are both still traveling and functioning, but with diminished resources, after nearly 50 years in the harshness of space. Source: NASA

That launch timing was super-critical to take advantage of an upcoming and very rare “grand alignment” of Jupiter, Saturn, Uranus, and Neptune. The Voyagers could fly by these planets using gravitational “slingshots” after their initial powered launch and boost phases.

Amazingly, they are both still functioning with greatly reduced capabilities after nearly 50 years in space, well beyond their planned ten-year mission, and have left our heliosphere and entered interstellar space. I haven’t been able to find out how the designers were able to use “ancient” components to create spacecraft that could survive the intense radiation of deep space; none of the documentation I have seen discusses that consideration.

There are other moderate-volume production examples from the past: the original Iridium satellite system (launched from 1987 to 1998) for worldwide voice-call connectively, which we now take as “no big deal”. It was a system using 66 MEO satellites (see “Eccentric Orbits: The Iridium Story”).

Once the premise of the concept was accepted, Iridium built the needed satellites and some spares in two batches, with all units in each batch identical. This allowed them to schedule parts procurement, assembly, test, and delivery in a very different way than the one-off approach that had been previously used.

Now we have GPS and GNSS with their hundreds of satellites, and the Starlink internet service with its thousands. Space-based systems and the need for space-rated components have clearly transitioned from single-unit designs to moderate volumes. While the numbers are orders of magnitude lower than for a mass-market consumer product such as a smartphone, it is still a meaningful shift.

We are in the beneficial “positive feedback” loop where demand for standard space-rated basic analog components is driving availability while such availability, in turn, is driving demand and opening new opportunities. We’ve seen this pattern many times in high-technology products and we’ll undoubtedly see it again.

Bill Schweber is a degreed senior EE who has written three textbooks, hundreds of technical articles, opinion columns, and product features. Prior to becoming an author and editor, he spent his entire hands-on career on the analog side by working on power supplies, sensors, signal conditioning, and wired and wireless communication links. His work experience includes many years at Analog Devices in applications and marketing.

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