Make Electronics

Chips, Ahoy! 149

Shopping List: Experiments 16 Through 24

FundAmentAls

Choosing chips (continued)

After the letters identifying the generation, you’ll find two (sometimes more)
numerals. These identify the specific function of the chip. You can ignore any
remaining letters and numerals. Looking back at Figure 4-3, the DIP chip part
number, M74HC00B1 tells you that it is a chip in the 74xx family, HC generation,
with its function identified by numerals 00. The surface-mount chip number,
74LVC07AD, tells you that it is in the 74xx family, LVC generation, with function
identified by numerals 07. For convenience we could refer to the first chip as a
“74HC00” and the second chip as a “74HC07” because, regardless of their differ-
ent manufacturers and package sizes, the fundamental behavior of the circuit
inside remains the same.

The purpose of this long explanation is to enable you to interpret catalog list-
ings when you go chip shopping. You can search for “74HC00” and the online
vendors are usually smart enough to show you appropriate chips from multiple
manufacturers, even though there are letters preceding and following the term
that you’re searched for.

Suppose a circuit requires a 74HC04 chip. If you search for “74HC04” on the
website of a parts supplier, you may find versions such as the CD74HC04M96 by
Texas Instruments, the 74HC04N by NXP Semiconductors, or MM74HC04N by
Fairchild Semiconductor. Because they all have “74HC04” in the middle, any of
them will work.

Just be careful that you buy the larger DIP-style package, not the surface-mount
package. If the part number has an “N” on the end, you can be sure that it’s a DIP
package. If there is no “N” on the end, it may or may not be a DIP package, and
you will have to check a photo or additional description to make sure. If the part
number begins with SS, SO, or TSS, it’s absolutely definitely surface-mount, and
you don’t want it. Many catalogs show photographs of the chips to assist you in
buying the right package style.

Manufacturer

Texas Instruments

Type of chip

7400 NAND gate

Generation of chip

High Speed CMOS

Package format

Dual in-line pin

Figure 4-4. Look for the chip family (74xx, in this case) with the correct generation
(HC, in this case) embedded in the number. Make sure you buy the DIP version, not
the surface-mount version. The manufacturer is unimportant.