REF

Definition

REF is a term that appears on IC package drawings in reference to dimensions. It stands for REFERENCE and indicates that this is a reference dimension, calculated or based on another dimension.

For example, the dimension from the first pin to the last pin in the row of a DIP (dual inline package) usually is tagged as REF because it is a multiple of the distance from pin-to-pin. In the case of a 16-pin DIP, the first pin to last pin dimension is 7 times the pin-to-pin dimension (7 spaces between 8 pins).