How to Read 74 Logic IC Part Numbers — SN74HC00N · 74HCT573PW · 74LVC1G08 (HC · HCT · LS · LVC families, function numbers, package letters)

Figure description: At the counter of an electronic parts shop, a customer holds a long-legged DIP chip (SN74HC00N) in one hand and a small SMD chip (HC00) in the other, comparing them and asking, “Is this one a 74HC00 too? The marking is shorter.” A female clerk in a red apron points to the small chip and answers, “Small chips are marked just HC00. It's the same chip!”

74 logic ICs are chips that contain basic logic circuits such as NAND gates, inverters, latches and shift registers. Many companies make them under the same numbers, so the part numbers look alike, but the family letters (HC · HCT · LS · LVC …) determine the usable voltage and input type, and the package letters and chip markings also differ from company to company.

All values were checked against TI and Nexperia datasheets. Click a part number to search stock in eGuro Part Search.

1. Reading one part number (SN74HC00DR · 74HCT573PW)

A 74 logic part number runs [company prefix] + 74 + family + function number + package (+ packing). TI adds SN at the front, while Nexperia starts with 74 without a prefix. If the 74 position reads 54, it is the grade for −55~125℃ use (TI SN54HC00 · SN54LS00). SN74HC00DR is TI · HC family · four 2-input NAND gates · SOIC · reel packing, and 74HCT573PW is Nexperia · HCT family · 8-bit D latch · TSSOP.

2. Family letters — LS · HC · HCT · AHC · LVC

HC is a CMOS family used at 2~6V, and HCT is the family that performs the same functions at 4.5~5.5V with TTL input levels (Nexperia 74HC_HCT00). LS is an older 5V family; TI SN74LS00 is rated 4.75~5.25V · 0~70℃. LVC runs at 1.65~5.5V and accepts inputs up to 5.5V, so it is used to bridge 3.3V and 5V circuits. The voltage ranges are the Recommended operating conditions values from each datasheet.

Figure description: A board on the counter is marked 3.3V. A customer holds bags labeled 74HC245 and 74HCT245 and asks, “HC or HCT, either one is fine, right?” A female clerk blocks the 74HCT245 bag with her palm, points to the 3.3V on the board and answers, “HCT won't work in a 3.3V circuit! It's for 4.5~5.5V.”

3. Function numbers — 00 · 04 · 138 · 245 · 573 · 595

The number after the family letters is the function. Parts with the same function number do the same job even in different families — 74HC00 · 74HCT00 · 74LS00 · 74AHC00 are all four 2-input NAND gates. However, as section 2 shows, their voltages and inputs differ, so don't swap them based on the function number alone. A part number containing 1G (74LVC1G08) is a small chip with just one gate.

4. Package letters — TI and Nexperia

At TI, N is DIP, D is SOIC and PW is TSSOP, and an R at the end means reel (Tape & Reel) packing — the datasheet lists SN74HC00DR as a 2,500-piece reel and SN74HC00N as a 25-piece tube. Nexperia also uses D · PW, but for the 20-pin wide SO, TI uses DW and Nexperia uses D, so the same letter can mean different sizes. How to read package sizes is covered in Component Package Names: A Complete Guide.
https://eguro.kr/board/view.html?b=library&id=59

5. Top markings — abbreviated

Large chips like DIP carry almost the full part number, but SMD parts such as SOIC and TSSOP are marked in abbreviated form, without the prefix and package letters. Very small chips such as 1G parts carry only a two- or three-character marking code like VE, so you have to look it up in the Marking table of that company's datasheet. The Nexperia 74LVC1G08 datasheet states that the pin 1 indicator is at the lower-left corner below the marking code.

6. Common part numbers decoded

All were decoded from the ordering information in TI · Nexperia datasheets. For part numbers that share a function number and differ only in family letters (e.g. 74HC573PW and 74HCT573PW), just remember that their voltage and input levels differ.

7. The most confusing pitfalls

• HC vs HCT — Same function, but HCT is 4.5~5.5V only. For 3.3V circuits, use a low-voltage family such as HC · LVC
• LS — 5V only (4.75~5.25V). TI SN74LS00 is 0~70℃
• Same name, different temperature — Even as 74HC00, TI SN74HC00 is −40~85℃ while Nexperia 74HC00 is −40~125℃
• Chip marking — SMD parts are abbreviated like HC00, and small 1G chips carry only a code like VE
• Package letters — 20-pin wide SOIC is DW at TI and D at Nexperia
• Trailing R — At TI, an R means reel packing; the chip is the same

8. What to check when substituting

• Function number — Is the number the same, like 00 · 245?
• Family and voltage — Is the circuit supply within that family's voltage range? (especially 3.3V circuits)
• Input level — HCT · AHCT for receiving 5V TTL signals, HC · AHC for CMOS-to-CMOS
• Package and pin count — Compare by actual package name (SOIC14 · TSSOP20, etc.) rather than letters
• Temperature and packing — 74 · 54 grade, temperature ranges that vary by company, reel · tube

Sources: TI SN74HC00 (SCLS181H) · SN74LS00 (SDLS025D) · SN74HCT245 (SCLS020H) · SN74LVC1G08 (SCES217AA), Nexperia 74HC_HCT00 · 74HC_HCT04 · 74HC_HCT14 · 74HC_HCT138 · 74HC_HCT245 · 74HC_HCT573 · 74HC_HCT595 · 74AHC_AHCT00 · 74LVC1G08 datasheets. Families, packages and markings may vary by company and product, so check the relevant datasheet before placing an actual order.