Electronic – Assigning numbers to the new components in Altium designer

There are two different systems for reffering to the size of SMT passives, confusingly these two systems use the same code for very different sizes.

The imperial codes are the dimensions in 10s of mils rounded to the nearest whole number (except in the case of 01005). The metric codes are the dimensions in tenths of a millimeter again rounded to the nearest whole number.

In my experiance the imperial system is more common.

"0603(1608 Metric)" is giving the size code in the imperial system first and then giving the equivilent metric size code in brackets.

If someone just says 0603 then they probablly mean "0603(1608 Metric)" but it's possible they mean "0201(0603 metric)".

In short

Parts inside component

A Component may have more than one parts, for ex: LM324 has 4 op-amps inside. With the part option, you select which one to use. Altium will create netlist for the pins with the part you have selected.

Part locked

Now, when you annotate the schematic, Altium not only changes the component names with ? (for ex U?), but also the parts. This may cause trouble in PCB because it effects witch pins of the part is connected to the rest of the circuit. If you select "part locked", Altium will keep all locked parts with your selections. For ex: A component with locked enable, lets say U?/part2 will not change to U1/part1 when you annotate schematics. It will be something like Uxx/part2 always.