kicad-developers team mailing list archive

[Simon Richter <Simon.Richter@xxxxxxxxxx>]

Hi,

I've started collecting a few ideas on use cases for the new component
format. I suspect others have done the same.

Is there a good place to collect all of these and/or collaboratively
edit them?

   Simon

# KiCad Schematic Components: Use Cases

This document tries to capture the use cases for the upcoming redesign of
schematic component handling in KiCad.

## Standard Components

 - standard components have distinctive symbols

 - different national and international standards might specify different
   symbols for the same component

 - users prefer different symbol sizes

 - components typically but not necessarily have a value (resistance,
   capacitance, inductance)

 - component values may be part numbers (e.g. diodes)

 - components might have additional values that may be relevant for the
   circuit in question (e.g. power rating, bandwidth) but often can be
   ignored (e.g. power rating in voltage dividers)

 - additional values may derive from the primary value (e.g. diode part
   number defines forward voltage), but need not

 - active components have power sources, but users might not want to
   annotate these for every instance

 - logic gates have no common representation of their power source for
   historical reasons

 - multiple standard components might be packed together into a single
   package (e.g. quad op-amps)

 - for multi-unit packages, power supply pins can be shared between units
   or groups of units

 - units in multi-unit packages may be exchangeable, even between different
   packages

 - constraints may apply to unit swapping (e.g. using the same power
   supply)

 - pins on the same unit may be swappable (e.g. AND/OR/XOR gates)

 - the same component may be available in different packages, with
   different pinouts

## Connectors

 - the electrical properties of connectors are dependent on the
   application and cannot be generalized in the component definition

 - standardized connectors exist with fixed mappings

 - some connectors have multiple different mappings (e.g. miniPCIe/mSATA)

 - when two interconnecting boards are designed, they require opposite
   connector definitions

## Integrated Circuits

 - ICs are typically represented as boxes with labeled pins

 - users might prefer to generate this representation from a table rather
   than paint it by hand.

 - ICs can have hundreds or thousands of pins, which makes the symbol
   unwieldly to use; users might prefer to create subunits

 - IC pins may be exchangeable, subject to constraints

 - it may be desirable to delay pin assignment until routing if multiple
   options exist

 - IC pins may be organized in banks sharing a common power supply or
   reference voltage

 - the same IC may be available in different packages, with different
   pinouts (e.g. TQFP and BGA variants)

 - ICs may be very similar between variants (e.g. different voltages);
   users might want to reuse information between them

 - pins may be configurable for different functions, subject to constraints

## Special-purpose ICs

 - users may prefer to use hand-drawn symbols even for ICs (e.g. a package
   containing protection diodes may represent them visually)

## ERC

 - component pins of active components are usually referenced to supply
   pins

 - connected components should usually, but not always be connected to the
   same supply rails

 - component pin type may be dependent on chip configuration

## Part Selection

 - part filtering may depend on supplementary values (e.g. resistor package
   depends on power rating)

 - single- and multi-unit parts might be candidates for components

 - unused units might need termination (e.g. op-amps)

## SPICE

 - schema components can be mapped to SPICE components for simulation

 - depending on the component type, the value needs to be translated in
   different ways (e.g. diodes are referenced by type, with forward voltage
   as fallback, while resistors just use the value)

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