Rad-Hard Roundup: Protecting Space Vehicles from Overcurrent Events2 days ago by Gary Elinoff
What's worse than overcurrent events? Overcurrent events in space.
Global radiation-hardened electronics are spiking in demand, according to Maximize Market Research. And that demand is fed by increasing demand for power management devices for space operations, specifically with communication satellites. Despite the high cost of developing and testing rad-hard devices, this market may also grow in tandem with the demand for MOSFETs, transistors, and diodes in aerospace applications.
Dealing with power anomalies in space requires specially-designed components like these to endure in high-radiation environments. In this short roundup, we present a few devices that live up to the challenges.
Designed for satellite applications, the RHRPMICL1A from STMicroelectronics is a radiation-hardened integrated current limiter. It can operate with supply voltages ranging from 8.5 VDC to 52 VDC and in certain cases, from 90 V or more.
The RHRPMICL1A. Image used courtesy of STMicroelectronics
The unit is designed to protect a power supply when, because of short circuits or other anomalies, the device demands excess current. It can replace or simply protect conventional fuses and operates in either re-triggerable, foldback, or latched modes. The unit typically draws 1.5 mA for internal operation and is designed to work with an external P-channel power MOSFET connected in a high-side configuration.
Block diagram of the RHRPMICL1A. Image used courtesy of STMicroelectronics
- Retriggerable mode. After the trip-off time, the current is cut off for a programmable period of time. It repeats this cycle until the overload clears.
- Foldback mode. In the event of a current overload, the RHRPMICL1A limits output current in a manner inversely related to the output voltage. It remains at a safe point even if the short-circuit persists.
- Latched mode. If overcurrent persists beyond the programmable trip-off time, the RHRPMICL1A turns off the current completely. Other signals must then be provided to turn the current back on.
Under low and high-ionizing dose rates, RHRPMICL1A's maximum immunity is 100 krad (silicon).
The EVAL-RHRICL1ALV1, Image used courtesy of STMicroelectronics
ST provides three separate evaluation boards for the RHRPMICL1A for foldback, latched, and re-triggerable modes: EVAL-RHRICL1AFV1, EVAL-RHRICL1ALV1, and the EVAL-RHRICL1ATV1, respectively.
The TPS7H2201-SP from Texas Instruments is a radiation-hardened load switch operating over a voltage range of 1.5 V to 7 V at up to 6 A. Designed for satellite power management, the dual-purpose device provides both programmable current limiting, and for devices requiring it, programmable slew rates.
Functional block diagram of the TPS7H2201-SP. Image used courtesy of Texas Instruments
The current limit can be programmed via an external resistor placed between PIN IL and the ground. The fast trip mode is set at 22 A and can’t be altered. Calculated, external capacitors can control both the time it takes for the TPS7H2201-SP to respond to an overcurrent and the time it takes to turn to current back on.
The TPS7H2201-SP includes an internal P-channel MOSFET. The unit features on-state resistances of 35 mΩs, 42 mΩs, and 47 mΩs at 25℃, 85℃, and 125℃, respectively. Two devices can be paralleled to double the current carrying capacity and/or reduce the on-state resistance.
The unit passes up to total ionizing dose (TID) 100-krad (silicon). TI provides extensive data on both testing methodology and results.
TI offers the TPS7H2201-SP single evaluation module. This will help customers to more quickly evaluate all of the device’s features.
TI's TPS7H2201-SP single evaluation module. Image used courtesy of Texas Instruments
The LX7712 from Microsemi (a Microchip company) is a radiation-hardened power control device designed for spacecraft. The IC includes a P-channel MOSFET switch. It can control DC loads of up to 5 A, and devices can be paralleled for greater currents.
In foldback current limit mode, the characteristics of the foldback current vs. the load voltage can be programmed via external resistors. The unit can also operate as a latchable current limiting mode.
Functional block diagram of LX7712. Image used courtesy of Microsemi (downloads as PDF)
The LX7712 operates over a temperature range of -55℃ to +125℃. Radiation hardening specifications include 100-krad TID and 50-krad enhanced low-dose-rate sensitivity (ELDRS).
Maximize Market Research forecasts that by 2026, the market for rad-hard electronics will heat up as the government continues to invest in ISR (intelligence, surveillance, and reconnaissance) operations, FPGA technology, and multicore processors.
As they do so, we can expect to see more ruggedized components come out of key semiconductor players, including ST, TI, Microsemi, Xilinx, Maxwell, and others.
Check out these other articles to learn how engineers and semiconductor suppliers are pushing innovations in the space industry.
What’s New in Space? Components Designed to Weather Aerospace and Defense
ChipSats—Hoards of Tiny Circuit Boards Sent to Space (or Attached to Cows)
“Honey, I Shrunk the NASA Payload”: A Call for Engineers to Help Send Mini Rovers to the Moon
Feature image (modified) used courtesy of STMicroelectronics
Do you work in the space industry? What design precautions do you take to account for overcurrent events? If you're able to do so, share your experiences in the comments below.