7400 Series - Part Numbering Scheme

Part Numbering Scheme

The part numbers for 7400 series logic devices often use the following naming convention, though specifics vary between manufacturers.

• First, although sometimes omitted, a two or three letter prefix which indicates the manufacturer of the device (e.g. SN for Texas Instruments, DM for National Semiconductor) although these codes are no longer closely associated with a single manufacturer, for example Fairchild Semiconductor manufactures parts with MM and DM prefixes, and none.
• A two-figure secondary prefix, of which the two most common are "74", indicating a commercial temperature range device and "54", indicating an extended (military) temperature range
• Up to four letters describing the logic subfamily, as listed above (e.g. "LS" or "HCT").
• Two or more digits assigned for each device, e.g. 00 for a quad 2-input NAND gate. There are hundreds of different devices in each family. The allocation of device numbers (and, with a few exceptions, the pin-outs) of the original 7400 family was carried across to the later families, and new numbers allocated for new functions, plus some of the competing CD4000 numbers and pin-outs were included over time. There is no pattern to the allocation of these numbers. The function and pin-out of the chip is nearly always the same for the same device number regardless of subfamily manufacturer – exceptions are discussed below.
• Additional suffix letters and numbers may be attached to indicate the package type, quality grade, or other information, but this varies widely by manufacturer.

For example SN74ALS245N means this is a device probably made by Texas Instruments (SN), it is a commercial temperature range TTL device (74), it is a member of the "advanced low-power Schottky" family (ALS), and it is a bi-directional eight-bit buffer (245) in a plastic through-hole DIP package (N).

Many logic families maintain a consistent use of the device numbers, as an aid to designers. Often a part from a different 74x00 subfamily could be substituted ("drop-in replacement") in a circuit, with the same function and pin-out yet more appropriate characteristics for an application (perhaps speed or power consumption), which was a large part of the appeal of the 74C00 series over the competing CD4000B series, for example. But there are a few exceptions where incompatibilities (mainly in pin-out) across the subfamilies occurred, such as:

• some flat-pack devices (e.g. 7400W) and surface-mount devices,
• some of the faster CMOS series (for example 74AC)
• a few low-power TTL devices (e.g. 74L86, 74L9 and 74L95) have a different pin-out than the regular (or even 74LS) series part.
• five versions of the 74x54 (4-Wide AND-OR-INVERT gates IC), namely 7454(N), 7454W, 74H54, 74L54W and 74L54N/74LS54, are different from each other in pin-out and/or function!).