Design Article
Latest radiation hardened power management products solve new design challenges
Josh Broline, Bernard Theju, Nick van Vonno, Intersil Corporation
3/26/2012 12:58 AM EDT
SEE mitigation design techniques
SEE mitigation calls for design techniques like redundancy and special device cell layout in order to mitigate the momentary deviations in the output caused by ion strikes. FPGA power requirements dictate that the VOUT single event transient deviation be limited to less that +/-5 percent, typically at an ion linear energy transfer (LET) value of 86 MeV•cm²/mg. In addition, these hardened devices are designed to be tolerant to the total ionizing dose environment, which in space applications typically consists of electrons and protons. All parameters of the device specification table are guaranteed to remain within the min/max limits specified in the Standard Microcircuit Drawing (SMD) up to the specified dose, typically 100 krad(Si) for the high dose rate of 50 – 300rad(Si)/s and 50krad(Si) for the low dose rate of 0.01rad(Si)/s, with the lower dose rate more accurately reflecting actual space conditions. The commercial equivalents on the other hand are not specified for these radiation environments, and will experience permanent damage, parameter shifts or potentially destructive output voltage transients.
Figure 2a: SET AT LET 86 MeV.cm²/mg VIN = 4.0V, VOUT=1.8V, IOUT=0.1A
Figure 2b: SET AT LET 86 MeV.cm²/mg AT VIN = 4.0V, VOUT=1.8V, IOUT=1.0A
Figure 2: Typical SET captures for the radiation hardened ISL75051SRH LDO at light and heavy load.
SEE mitigation calls for design techniques like redundancy and special device cell layout in order to mitigate the momentary deviations in the output caused by ion strikes. FPGA power requirements dictate that the VOUT single event transient deviation be limited to less that +/-5 percent, typically at an ion linear energy transfer (LET) value of 86 MeV•cm²/mg. In addition, these hardened devices are designed to be tolerant to the total ionizing dose environment, which in space applications typically consists of electrons and protons. All parameters of the device specification table are guaranteed to remain within the min/max limits specified in the Standard Microcircuit Drawing (SMD) up to the specified dose, typically 100 krad(Si) for the high dose rate of 50 – 300rad(Si)/s and 50krad(Si) for the low dose rate of 0.01rad(Si)/s, with the lower dose rate more accurately reflecting actual space conditions. The commercial equivalents on the other hand are not specified for these radiation environments, and will experience permanent damage, parameter shifts or potentially destructive output voltage transients.
Figure 2a: SET AT LET 86 MeV.cm²/mg VIN = 4.0V, VOUT=1.8V, IOUT=0.1A
Figure 2b: SET AT LET 86 MeV.cm²/mg AT VIN = 4.0V, VOUT=1.8V, IOUT=1.0A
Figure 2: Typical SET captures for the radiation hardened ISL75051SRH LDO at light and heavy load.
Samples were tested at an ion LET of 86 MeV•cm²/mg at an input voltage of 4.0V and an output voltage of 1.8V. The left traces are for an output current of 0.1A and the right ones are for 1.0A. The lower (blue) traces show a 40mV increase of the output voltage for the 0.1A case and a 30mV increase for the 1.0A case, which represents approximately 2 percent of the output voltage.
With a point of load regulator that is specifically designed and qualified for the space environment, these challenges can be met head on. For example, the above transient plots above show that the single event transients (SET) observed under beam are well within the +/-5 percent requirement. Fast transient response and high slew rate require compensated wide bandwidth closed loop feedback, which will remain stable over the defined COUT and load range. To some degree this response time defines the recovery time from SEE as well, so a fast system is likely to show a narrow transient lasting for less than 5µs when compared to a slow system which can take a couple of milliseconds to recover. SET performance of at least less than +/-5 percent is critical to a space environment power supply, otherwise it will be impossible to meet the overall +/-5 percent FPGA voltage tolerance.
There are various reasons why designers may prefer a hybrid module or discrete component solution over a monolithic integrated circuit solution. A lot of it is driven by application specific reasons such as power dissipation requirements or layout considerations. A highly integrated hybrid is typically used when board space is a major constraint, and a discrete solution may be attractive when output power requirements are high. A monolithic IC solution is a good balance between these two alternative power supply designs. In a monolithic voltage regulator, the power MOSFETs and drivers are integrated onto the silicon. This typically reduces the overall power management solution footprint versus discrete solutions and improves the overall reliability of the system as there are now fewer solder joints that can fail over time. Despite the FETs being on silicon, IC devices can still handle a significant amount of power. For example, the new ISL70002SEH point of load (POL) regulator can output > 55 watts at a junction temperature of 150oC. This allows the designer to use a compact solution versus a discrete solution and still meet most of the load power requirements. Since hybrid solutions tend to integrate most components within the same large enclosure, the user does not have very many options when designing in the hybrid. With fewer external components needed for the integrated POL versus a discrete solution, more time can be focused on the core portion of the system design and less on procuring components or working on the power supply design and layout.
The next generation monolithic power management components being released today are critical solutions for space power designers’ needs for low power dissipation and weight, which are very critical in satellite systems with ever shrinking payload size. Their simplicity greatly reduces the design cycle time, while still providing “commercial-like” features liked, tight tolerances, good stability and intelligent control. The smaller footprint also permits mounting the voltage regulator closer to the actual application printed wired board (PWB) as compared to discrete / hybrid solutions, where the power solution may be on an adjacent power board or at a distance.
About the authors:
Josh Broline is a Lead Marketing Engineer under Intersil’s High Reliability products group responsible for the Space & Harsh Environment product lines. He has 10 years of service with Intersil, the first 5 years as a Product Engineer and the last 5 as a marketing engineer responsible for various product lines. Josh has a BSEE from University of Central Florida and an MBA from Florida Institute of Technology.
Theju Bernard is Principal Applications Engineer working in the High Reliability products group at Intersil Corporation. He is responsible for the new product development in the Space and Harsh environment arena. He has 29 years of industrial experience of which the last eight have been with Intersil. He served as Application Engineer in the Consumer group for three years and five years to date as Application Engineer in the High Reliability group. Theju holds a BSEE from the University of Mysore, India.
Nick van Vonno is a Principal Engineer in Intersil’s High Reliability products group. He has 42 years of service with Intersil and its predecessors in a number of technical and management posts. He is currently responsible for radiation effects research, customer support and technology development for the product line. Nick has a BSEE from the University of Florida and is a Senior Member of IEEE. He received the IEEE Radiation Effects Award in 2009.
With a point of load regulator that is specifically designed and qualified for the space environment, these challenges can be met head on. For example, the above transient plots above show that the single event transients (SET) observed under beam are well within the +/-5 percent requirement. Fast transient response and high slew rate require compensated wide bandwidth closed loop feedback, which will remain stable over the defined COUT and load range. To some degree this response time defines the recovery time from SEE as well, so a fast system is likely to show a narrow transient lasting for less than 5µs when compared to a slow system which can take a couple of milliseconds to recover. SET performance of at least less than +/-5 percent is critical to a space environment power supply, otherwise it will be impossible to meet the overall +/-5 percent FPGA voltage tolerance.
There are various reasons why designers may prefer a hybrid module or discrete component solution over a monolithic integrated circuit solution. A lot of it is driven by application specific reasons such as power dissipation requirements or layout considerations. A highly integrated hybrid is typically used when board space is a major constraint, and a discrete solution may be attractive when output power requirements are high. A monolithic IC solution is a good balance between these two alternative power supply designs. In a monolithic voltage regulator, the power MOSFETs and drivers are integrated onto the silicon. This typically reduces the overall power management solution footprint versus discrete solutions and improves the overall reliability of the system as there are now fewer solder joints that can fail over time. Despite the FETs being on silicon, IC devices can still handle a significant amount of power. For example, the new ISL70002SEH point of load (POL) regulator can output > 55 watts at a junction temperature of 150oC. This allows the designer to use a compact solution versus a discrete solution and still meet most of the load power requirements. Since hybrid solutions tend to integrate most components within the same large enclosure, the user does not have very many options when designing in the hybrid. With fewer external components needed for the integrated POL versus a discrete solution, more time can be focused on the core portion of the system design and less on procuring components or working on the power supply design and layout.
The next generation monolithic power management components being released today are critical solutions for space power designers’ needs for low power dissipation and weight, which are very critical in satellite systems with ever shrinking payload size. Their simplicity greatly reduces the design cycle time, while still providing “commercial-like” features liked, tight tolerances, good stability and intelligent control. The smaller footprint also permits mounting the voltage regulator closer to the actual application printed wired board (PWB) as compared to discrete / hybrid solutions, where the power solution may be on an adjacent power board or at a distance.
About the authors:
Josh Broline is a Lead Marketing Engineer under Intersil’s High Reliability products group responsible for the Space & Harsh Environment product lines. He has 10 years of service with Intersil, the first 5 years as a Product Engineer and the last 5 as a marketing engineer responsible for various product lines. Josh has a BSEE from University of Central Florida and an MBA from Florida Institute of Technology.Theju Bernard is Principal Applications Engineer working in the High Reliability products group at Intersil Corporation. He is responsible for the new product development in the Space and Harsh environment arena. He has 29 years of industrial experience of which the last eight have been with Intersil. He served as Application Engineer in the Consumer group for three years and five years to date as Application Engineer in the High Reliability group. Theju holds a BSEE from the University of Mysore, India.Nick van Vonno is a Principal Engineer in Intersil’s High Reliability products group. He has 42 years of service with Intersil and its predecessors in a number of technical and management posts. He is currently responsible for radiation effects research, customer support and technology development for the product line. Nick has a BSEE from the University of Florida and is a Senior Member of IEEE. He received the IEEE Radiation Effects Award in 2009.----------------------------
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