How to Read ST General-Purpose Part Numbers — Suffix Letters in L7805CV · LM317T · STP55NF06 (Package · Grade · Packing)

Illustration: A customer holds a large three-lead part (L7805CV) and a flat part on a reel (L7805CD2T-TR) and asks, “They're both 7805, so they're the same, right?” A female staff member in a red apron answers, “The chip is the same, but the suffix is different. V is TO-220, D2T is D²PAK on reel!”

ST (STMicroelectronics) parts come with many different order code suffixes, even for the same chip. A single 5V regulator alone is split into L7805CV · L7805CV-DG · L7805CDT-TR · L7805CD2T-TR · L7805CP. The suffix letters mostly indicate the package (body shape), the grade (temperature · accuracy), and the packing (tube · reel).

This post is based only on the Order codes tables and Marking sections of ST datasheets. Where ST gives no separate explanation and we read the meaning by comparing several datasheets, it is marked [Inferred].

1. Reading a regulator one field at a time — L7805CD2T-TR

ST regulators follow the order series → voltage → grade → package → packing. In LD1117, however, the package letter comes before the voltage (LD1117S33TR = LD1117 + S (SOT-223) + 33 (3.3V) + TR (reel)). The order differs slightly by series, so check the tables in sections 2 and 3.

2. Grade letters — the same C means different things in different series

All temperatures are based on the chip's internal temperature (junction temperature, TOP), and ±% is the output voltage tolerance on page 1 of each datasheet.

For LM317 the grade letter is B. LM317T is 0~125℃, LM317BT is −40~125℃, and LM217T, with a different prefix, is −25~150℃ (DS0433 Table 1).

3. Package · packing suffixes

Reel quantities are the Base quantity values in each datasheet's tape and reel table (L78 · LM317 D²PAK 1,000 · L78 · L78M · LD1117 DPAK 2,500 · LD1117 · LM317 SOT-223 1,000).

A footnote to L78L Table 29 states that for TO-92 -AP (Ammopak) and TR (tape and reel), “pins are shaped according to tape and reel specifications” — the leads come bent to fit the tape specification. For hand insertion use Z (bag); for automatic insertion machines use -AP · TR.

4. Same letter, different package — traps between series

Even within ST, TO-220 is V for L78 but T for LM317. The T in LM317T and the V in L7805CV are the same TO-220, and D2T · DT also contain a T, so it is easy to get confused. Don't memorize single letters like "T means TO-220" — check the order table for each series.

Even with the same L78L05AC, the body is completely different depending on Z · U · D. The pin order also differs by package (TO-92 is OUT · GND · IN), so check the pinout table in post 96 as well.

5. Regulator chip marking ≠ order code

L78L Table 30 (Marking information) shows that on TO-92, AC · AB · C are all marked the same L78L05A, and on SOT-89 only a two-character voltage code such as 8C is printed. So you cannot tell the grade (AB · AC · C) or packing (Z · Z-AP · ZTR) from the chip alone. Verify the actual part by the order code on the bag or reel label.

6. Reading a MOSFET one field at a time — STD30NF06LAG

ST does not publish an official document on its MOSFET part numbering. The breakdown above comes from matching datasheet order tables (Order code · Package · Marking) with the technology names in the titles, so the letter meanings for ③ · ⑤ · ⑥ · ⑦ are [Inferred]. Package and packing are stated directly in the order table, so they are certain — check those first. MOSFET part numbers in general (2SK · IRF · TK) are covered in post 56.

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7. The letter after ST = package

The package and packing in the table are the values from each datasheet's order table. The rule itself that the third letter indicates the package is [Inferred], and the STF20N65M5 datasheet revision history shows other combinations such as STFI · STFW, so check any unfamiliar letter against the datasheet.

8. The most common mistake — STP and STF are the same chip in different bodies

Illustration: A customer looks at a part with an exposed metal tab (STP13NM60N) and a part with an all-black plastic body (STF13NM60N) and asks, “It's only one letter different, so either one is fine, right?” A female staff member in a red apron answers, “P is TO-220, F is the insulated TO-220FP. The power is different — 90W vs 25W!”

The three part numbers share the same chip: 600V · 11A · on-resistance max 360mΩ (DS14455 · DS14454 · DS14452 Table 1). But TO-220FP is an insulated package with the metal tab also covered in plastic, so it dissipates heat less well and the allowed power drops from 90W → 25W. In return, only the STF has an “Insulation withstand voltage” of 2.5kV (three leads ↔ heatsink), so it can be mounted on a heatsink without an insulating pad.

9. The middle numbers — current · voltage "class" (not exact values)

The first number appears to be roughly the current class and the second the voltage class [Inferred]. But the units of the second number are mixed — 06 · 6 · 4 · 10 are ×10 (60 · 60 · 40 · 100V); the 60 in STP10NK60Z is 600V, but the 60 in STS4DNF60L is 60V; and the 55 in STP80NF55 is 55V as is. The first number also varies: 240 is 180A and 140 is 120A. Don't assume voltage · current from the numbers alone — check the table on page 1 of the datasheet (VDS · ID). The trailing -06 in STP80NF55-06 is an extra part-number suffix, but the datasheet gives no explanation of its meaning.

10. Technology letters — NF · NK · NM · M2 · DM2 · M5 · F7

The technology names on the right are exactly as written in each datasheet's title · description. The pairing of part-number letters with technologies is [Inferred]. When looking for substitutes, if the technology letters differ, switching characteristics (gate charge · diode recovery) may differ even at the same voltage · current, so compare datasheet values. Replacing a part that emphasizes a "fast-recovery diode", such as DM2, with M2 can cause problems in bridge circuits.

11. Final suffix letters — L · Z · D · AG · T4 · -1 · -2 · FP

L · Z · AG were matched to the wording in the Features on page 1 of each datasheet, so the letter meanings are [Inferred]. T4 is not always added either — STB55NF06 comes in Tape and reel without T4 (Doc ID 7544 Table 1). For automotive · vehicle electronics customers, first check whether the part number carries AG and whether a standard part number (without AG) is acceptable instead.

12. MOSFET chip marking ≠ order code

Older part numbers keep the package letter (P · B · W) at the front of the marking, but recent datasheets use the same marking without the package letter, such as 13NM60N. AG · T4 are not printed on the chip. You cannot tell from the chip marking alone whether it is automotive or on reel, so verify by the order code on the packing label.

Sources: ST datasheets — L78 (DS0422 Rev 38) · L78L (DS0424 Rev 30) · L78M (DS0425 Rev 24) · L79 (DS0428 Rev 24) · LD1117 (DocID2572 Rev 38) · LM217/LM317 (DS0433 Rev 22) · STB55NF06/STP55NF06 (Doc ID 7544 Rev 11) · STP80NF55-06 (Rev 8) · STP10NK60Z (DS2635 Rev 12) · STP13NM60N (DS14455) · STF13NM60N (DS14454) · STI13NM60N (DS14452) · STU10NM60N (DS14497) · STD30NF06LAG (DocID029664) · STL140N4F7AG (DocID028588) · STL130N6F7 (DS10891) · STH240N10F7-2 (DS10259) · STN3NF06L (DocID7798) · STS4DNF60L (Doc ID 6121) · STW70N60M2 (DS9514) · STW48N60DM2 (DS10603) · STW88N65M5 (DS8771) · STF20N65M5 (DS9474) (checked 2026-11-04). ST does not publish a MOSFET part-numbering document, so items marked [Inferred] were read from the order tables. Always confirm with the latest datasheet for the specific part number before ordering.