A Radiation-Tolerant Microcontroller: Designed for Critical Space and Aerospace Applications

Microchip's ATmegaS64M1 AVR microcontroller offers enhanced radiation protection, an extended temperature range, and increased reliability for space and aerospace applications.

Microchip recently introduced their new radiation-tolerant microcontroller, the ATmegaS64M1. This MCU (microcontroller) is offered in two package material types (see figure below). One package, intended for aerospace applications, is a 32-lead plastic thin quad flat package (TQFP). The other package type—the advertised radiation-tolerant package that is designed for space environments—is hermetically sealed and comes in a 32-lead ceramic quad flat package (CQFP).

Figure 1. The two MCU package types. This is probably obvious, but the one on the left is the aerospace-intended plastic package while the one on the right is the radiation-tolerant ceramic package for space applications. From the ATmegaS64M1 MCU flyer (PDF).

An "Extended" Temperature Range

Although the ATmegaS64M1 microcontroller's overview mentions that this MCU is designed for  "extended" temperature applications, I don't think this statement fully captures the IC's operating temperature range. After all, this device is designed to the widest-ranging temperature grade—the military-grade—of -55°C to 125°C. Of course this higher-than-normal temperature rating will surely carry a price premium, but if you're sending an MCU, or really any electronics, into space, you definitely want this feature and don't want to quibble on its price.

 

Figure 2. The MCU is designed at military-grade temperature specs. Table taken from the datasheet (PDF).

Achieving 1 MIPS per MHz

This microcontroller is advertised as having an instruction set consisting of 131 instructions, with most of them being executed in a single clock cycle. And it's these single-clock-cycle instructions, according to its datasheet, that allow the ATmegaS64M1 to offer performance approaching 1 MIPS per MHz. Also, system designers can balance the MCU between power consumption (which is critically important for space applications) and processing speeds.

 

Figure 3. Processor specs, from the datasheet (PDF).

Space Quality Grade

Described in the datasheet as being "space quality grade," this MCU has been "developed and manufactured according to the most stringent requirements of MIL-PRF-38535." Perhaps unfamiliar, if not utterly unknown, to most practicing engineers, MIL-PRF-38535 is a United States military specification that dictates the performance and testing requirements of single-die ICs. This all sounds very impressive...and yet very expensive in terms of product development and purchase price. But if you're in the business of putting satellites in space, you most likely want your ICs to meet these rigorous requirements.

Fully Featured

It would be reasonable to assume that this microcontroller offers limited functionality, since a significant portion of the development effort must have been focused on making the device suitable for space applications. But the feature set seems quite robust: Digital peripherals include CAN bus support, UART, and PWM generation. On the analog side, the chip has an internal reference voltage, a 10-bit ADC with internal programmable gain, a 10-bit DAC, four analog comparators, and an on-chip temperature sensor. It also has an internal oscillator, so no external clock circuitry is required in applications that don’t need high-precision timing.

In Production, but the Datasheet Is Still Preliminary

Although the IC, according to the overview, is listed as "in production" and has a 361-page datasheet, the datasheet itself is still a preliminary document. So keep this in mind when you come across phrases such as "To Be Defined after characterization" and "To Be Confirmed after characterization." Honestly, I don't think Microchip is being hasty by releasing a production-level product while having this information "missing" from the datasheet. I imagine that most semiconductor manufacturers aren't readily geared-up for testing and troubleshooting radiation-tolerant and military-grade ICs.

Are Radiation-Tolerant Devices Necessary?

When I first came across this radiation-tolerant MCU, my initial thinking was: is this radiation-tolerant device really necessary!? But after reading the product's flyer, my thought process quickly changed to asking myself these questions: Why aren't there more of these radiation-tolerant products (not just MCUs) available? With all the recent SpaceX launches (which I feel are truly epic given their now-repeated first stage vertical landings), do the recently launched/deployed commercial satellites use radiation-tolerant, or otherwise space-hardened, electronics? If so, which manufacturer(s) are providing these devices?

 

Figure 4. Radiation-tolerant devices will be needed for future space applications. Image taken from the ATmegaS64M1 MCU flyer (PDF).

Have you had a chance to use, or are you planning to use, this new radiation-tolerant microcontroller in any designs? If so, leave a comment and tell us about your experiences.