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DESIGN.md

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Design Guidelines

General

  • Description should end in (FOOTPRINT)

  • Seperate power units: orient vertically, pins at +/- 0.4in with 0.15in length

  • Text should be 50 mil in general

  • Pin length, numbering, general naming:

    • ICs: at least 0.15in
    • Discretes: when omitting pin numbers is practical, keep short for maximum wiring flexibility
    • Omitting pin numbers is allowed on discrete devices, but consider leaving the numbers for devices with nonstandard pinouts
    • Name all pins. Hide names when the symbol graphic labels the pin instead (transistor BCE, etc)
    • Prefer overbar for inverted pins with names, inversion circle for inverted pins without names. Don't combine the two!
  • In manufacturer libraries, name parts according to manufacturer naming scheme.

  • One part per footprint; specify footprint in Footprint field

  • For parts with a large number of variants (e.g. fixed-voltage regulators), a placeholder in the name is acceptable: LM1117DT-v.v

  • Prefer logical schematic to blank parts with names - e.g., use buffer symbol in buffers, not just pins named IN and OUT.

  • Include Manuf and PN lines.

  • Include bomtool BOM lines whenever possible.

Power supply naming

  • Do not follow manufacturer naming
  • For single rail parts, name main supply V+ (not VCC, VDD)
  • For multi-rail parts, name main supply according to use when possible (VCORE, not V1.2)
  • Ground is GND, not VSS

Template parts

  • Do not include description
  • Do not include footprints

Very large logic (FPGA, large MCU, etc)

  • Use "bracketed" multi-part style

Small logic (7400, etc)

  • Use traditional (non-IEC) symbols for very simple like NAND
  • Use IEC or IEC-like symbols for more complex like shift register
  • Use separate power units