Design Article
Implementing analog functions in rugged, rad-hard FPGAs
Allan Chin and Luciano Zoso, Stellamar
2/11/2013 2:21 PM EST
Performance plus applications
Current performance is up to 15 bits of resolution and several hundred kilohertz of bandwidth. Bandwidth depends on the selected resolution. This level of performance is suitable for a host of applications including sensors (temperature, pressure, voltage, current and acceleration), touchscreen integration, high-quality voice and motor control.
As an example, many design teams use a radiation-hardened, 12-bit, 10-MHz bandwidth ADC part for monitoring onboard temperature and voltage. Some FPGAs, such as the Xilinx Virtex-5QV space-grade FPGA, even have embedded diodes highlighting the importance of the temperature-sensing function. However, normal bandwidths for these types of measurements are 0.5 Hz to 10 Hz, so using bandwidth in the megahertz is like driving the head of a pin with a sledgehammer. A Digital ADC IP core on a radiation-hardened FPGA can get down to 0.5-Hz bandwidth per channel and can consume less than 6 mW, compared with 335 mW for the external part. Why waste critical board space and power for such a low-level task?
Controlling DC/DC power management
Power management is becoming a larger part of overall system design. Sometimes a single design can include more than 30 power supplies. External radiation-hardened DC/DC converters retain the same difficulties as external ADCs. Thus, the use of these parts to control power complexity in high-reliability applications does not scale well.
All-digital DC/DC controller IP now exists to take advantage of radiation-hardened FPGAs’ processes and to allow for simplification of control, redundant power supplies, infinite sequencing and infinite throttling (see Figure 2). You will still need an external power transistor, but this can be much easier to work with than a full DC/DC converter part.
Figure 2: Example DC/DC controller block diagram
Current performance is up to 15 bits of resolution and several hundred kilohertz of bandwidth. Bandwidth depends on the selected resolution. This level of performance is suitable for a host of applications including sensors (temperature, pressure, voltage, current and acceleration), touchscreen integration, high-quality voice and motor control.
As an example, many design teams use a radiation-hardened, 12-bit, 10-MHz bandwidth ADC part for monitoring onboard temperature and voltage. Some FPGAs, such as the Xilinx Virtex-5QV space-grade FPGA, even have embedded diodes highlighting the importance of the temperature-sensing function. However, normal bandwidths for these types of measurements are 0.5 Hz to 10 Hz, so using bandwidth in the megahertz is like driving the head of a pin with a sledgehammer. A Digital ADC IP core on a radiation-hardened FPGA can get down to 0.5-Hz bandwidth per channel and can consume less than 6 mW, compared with 335 mW for the external part. Why waste critical board space and power for such a low-level task?
Controlling DC/DC power management
Power management is becoming a larger part of overall system design. Sometimes a single design can include more than 30 power supplies. External radiation-hardened DC/DC converters retain the same difficulties as external ADCs. Thus, the use of these parts to control power complexity in high-reliability applications does not scale well.
All-digital DC/DC controller IP now exists to take advantage of radiation-hardened FPGAs’ processes and to allow for simplification of control, redundant power supplies, infinite sequencing and infinite throttling (see Figure 2). You will still need an external power transistor, but this can be much easier to work with than a full DC/DC converter part.
Figure 2: Example DC/DC controller block diagram
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