How to Read onsemi Power IC Part Numbers — NCP1117·MC34063·MC7805: NCP·NCV·MC prefixes and T3G·RKG suffixes

Image description: At the counter of an electronic components shop, a customer holds two component bags labeled NCP1117 and NCV1117 and asks, “P and V — just one letter apart, so they're the same, right?” A female clerk in a red apron points to the NCV bag and answers, “NCV is automotive!”

onsemi is a US semiconductor company that makes many power ICs, regulators and transistors. In Guro, onsemi part numbers such as NCP1117 · MC34063A · MC7805 · LM317 are frequently searched, but the actual ordering part numbers carry long suffixes, like NCP1117ST33T3G · MC7805BDTRKG. The prefix tells you general-purpose or automotive, the middle letters tell you temperature · accuracy · package, and the suffix tells you the packaging unit.

All values were checked against the ordering information, marking and temperature tables of onsemi datasheets (NCP1117 · MC34063A · MC7800 · MC78L00A · LM317 · NCV4274). In this post, what the datasheets state as rules is kept separate from what can be inferred by matching entries in the ordering information tables. Click a part number to search stock in eGuro Part Search.

1. Decoding one part number (NCP1117ST33T3G)

onsemi power IC part numbers usually follow the order [prefix + function number] + temperature · accuracy letters + package + voltage + packaging + G. NCP1117ST33T3G is a general-purpose 1A LDO · SOT-223 · 3.3V · 4,000-piece reel · Pb-free. Page 1 of the NCP1117 datasheet states ST SUFFIX = SOT-223, DT SUFFIX = DPAK, and numbers like 33 · 50 match the output voltage column of the ordering information table.

2. Prefixes — NCP · NCV · MC · LM

The only prefix whose meaning the datasheet spells out is NCV. The original text reads “NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC−Q100 Qualified and PPAP Capable” — meaning it has automotive component qualification (AEC-Q100) and changes to manufacturing site or process are controlled separately. So even for the same MC7805, the automotive version changes its prefix to NCV, as in NCV7805BTG. The meanings of NCP · MC · LM are not stated in the datasheets.

Sometimes part of the number changes too: the automotive LM317 is NCV317, and the automotive version of the MC34063A family is NCV33063A.

3. Temperature letters — same part number, different temperature

Even with the same function, a single middle letter in the part number changes the usable temperature. All values are from the temperature tables and footnotes in the datasheets.

4. Accuracy letter — one A makes ±2% vs ±4%

For MC7805, an A before the temperature letter (B · C) indicates a version with a tighter output voltage range. The NCV4274 datasheet states directly “2.0% or 4.0% depending on the version”, and in the ordering table the part numbers with A are the 2% versions. The MC7800 datasheet also mentions a 1.5% version, but the table does not show which part number it is, so it is left out here.

5. Package letters — ST · DT · D2T · T · D · P

Image description: A customer holds an 8-pin DIP chip and asks, “MC78L05ACP has a P too, so it's this one, right?” A female clerk shows a small 3-lead part and answers, “This P is a 3-lead TO-92!”

6. Suffixes — packaging unit and G

The final G marks a Pb-free product. The marking description states “G = Pb−Free Package”, and every package entry in the ordering table carries “(Pb−Free)”. The letters before it, such as T3 · RK · R4 · R2, are the reel · rail · bag packaging units. onsemi datasheets do not explain these letters in words, so the list below pairs each one with the packaging listed on the same row of the ordering table.

The datasheets do not explain why the same DPAK reel has separate RK · T4 · T5 codes, or the differences between TO-92 RA · RE · RM · RP (such as lead-forming shapes). If you need packaging that fits your production line, check with that specific part number.

7. Reading the top marking

Small packages are not marked with the full part number but with abbreviated characters. Below are the markings exactly as shown in the datasheets (MARKING DIAGRAMS).

Marking description: A = assembly location, L · WL = wafer lot, Y · YY = year, W · WW = work week, G or • = Pb-free. The trailing T (NCP1117I) · V (NCV1117) are differences visible in the marking diagrams; the datasheets do not explain them in words.

8. Frequently searched part numbers decoded

All of these part numbers appear verbatim in the ordering information tables of onsemi datasheets. In the NCV4274 family, only NCV4274ADT50RKG · NCV4274AST33T3G are currently sold and the rest are discontinued; SC33063ADR2G in the MC34063A datasheet is also discontinued.

9. What to check when substituting

• NCP ↔ NCV — Even if the chip function is the same, only NCV has automotive qualification (AEC-Q100). Use NCV in automotive applications
• Temperature letter — B can replace MC7805C (from 0℃), but C in place of B can cause problems in winter or outdoors. The same goes for MC34063A ↔ MC33063A
• Accuracy A — don't put a ±4% part without A where ±2% is required
• Package letters — the same P can be an 8-pin DIP or TO-92, and D2PAK is also written D2T or DS. Confirm by package name
• Output voltage — NCP1117 offers different voltages in SOT-223 and DPAK (2.85V is DPAK only)
• Discontinued — for part numbers marked DISCONTINUED in the datasheet, such as NCV4274 · SC33063A, check for a replacement

Sources: ordering information, marking and temperature tables of the onsemi NCP1117/D (Rev. 31, 2021-08) · MC34063A/D (Rev. 27, 2026-08) · MC7800/D (Rev. 29, 2021-11) · MC78L00A/D (Rev. 21, 2025-07) · LM317/D (Rev. 18, 2026-09) · NCV4274/D (Rev. 17, 2024-07) datasheets. Packaging letters (T3 · RK · R4 · R2, etc.) were paired from the ordering information tables; before placing an actual order, confirm with the datasheet for that part number.