• Relevant Resources

Pumpkin CubeSat Kit OBC

http://smallformfactors.mil-embedded.com/articles/designing-rad-hard-cubesat-onboard-computer/

• Uses radiation-hardened (aka rad-hard) components
  • Radiation hardening: the process of making electronic components and circuits resistant to damage or malfunction caused by high levels of ionizing radiation
• MCU: Radiation-hardened VA10820 ARM Cortex-M0
• External Memory
• PC/104 connector
  • PC/104: A family of embedded computer standards. The name comes from the 104 pins on the inter-board connector
• Rad-hard Intersil ISL706A voltage supervisory circuit
  • It has 3 functions:
    1. Hold the MCU in reset until the power supply reaches an appropriate level to power the MCU
    2. Observe the system power supply as a latch-up warning monitor
    3. Act as an additional independent watchdog
       1. Watchdog: a timer that monitors microcontroller (MCU) programs to see if they are out of control or have stopped operating.
• Cobham Aeroflex RHD5950 14-bit ADC
  • https://caes.com/sites/default/files/documents/Datasheet-RHD5950.pdf
  • ADC channels are connected to analog input signal lines
    • One ADC channel monitors the system voltage supply rail
    • Another channel is connected to a resistance temperature detector (RTD)
• LDOs
  • A low-dropout regulator is a DC linear voltage regulator that can regulate the output voltage even when the supply voltage is very close to the output voltage.
  • 2 Intersil ISL7502SEH rad-hard LDOs
    • One for 3.3V and one for 1.5V
• Power rails
  • System powered by 5V supply
  • There are 3 voltage supply rails
    • 1.5V: required for the MCU core voltage
      • I think the RM46 needs 1.14 to 1.32 V
    • 3.3V: All I/O on the board use 3.3V signalling
    • 5V: Supplied the 2 LDOs and the ADC
• MCU is supplied by a rad-hard 50 MHz clock device
• UART-to-USB interface
  • Used for development work. Not intended for use in orbit.
  • The interface is only powered when a USB cable is plugged in, so there won't be any problems in the circuit if the component's affected by radiation.
• HI-3110 CAN controller with built-in transceiver
  • UART, SPI, and I2C are good for onboard communications
  • CAN interface is a good option for inter-board communications
• JTAG connector for programming and debugging
• RBF Switch
  • "Remove before flight" switch
  • RBF circuit ensures that the satellite starts operation only after the ejection from the launch vehicle.
    • https://www.aero.iitb.ac.in/satelliteWiki/index.php/SNAP_(Remove_Before_Flight)

Development of an onboard computer (OBC) for a CubeSat