Zener Diode Voltage Codes at a Glance — 5.1V Is BZX84C5V1·BZT52C5V1·MMSZ5231B·1N4733A, Voltage Tables by Series

Image description: A customer says, “A 5.1V Zener, please.” A female clerk in a red apron lays out four envelopes labeled BZX84C5V1 · BZT52C5V1 · MMSZ5231B · 1N4733A and answers, “They're all 5.1V, only the size is different!”

A Zener diode is a diode that conducts current at a set voltage to hold the voltage steady. Even for the same 5.1V Zener, the part numbers differ completely by package and company, such as BZX84C5V1 · BZT52C5V1 · MMSZ5231B · 1N4733A. This article puts 10 commonly used Zener series into one table so that you can find the part number from the voltage, or the voltage from the part number, right away.

All values were checked against 14 official datasheets from Nexperia · onsemi · Diodes Incorporated · Vishay. Click a part number to find stock with eGuro Part Search.

1. Part numbers that show the voltage and those that don't

For part numbers with the voltage written at the end, like BZX84C5V1, you can read the voltage from the part number alone. Part numbers made of serial numbers, like 1N4733A · MMSZ5231B, contain no voltage in the digits, so you have to look at the datasheet table (or the table in section 6 of this article).

2. 5V1 = 5.1V — how voltage is written

Voltages below 10V are written with V in place of the decimal point, as in 5V1 (5.1V) · 3V3 (3.3V); from 10V up, only whole numbers such as 12 · 24 are used. The datasheets do not explain this rule in words, but the part numbers and voltages in every table are paired this way, and Diodes gives the example above directly. Even within BZX84, Nexperia inserts a hyphen as in BZX84-C5V1, while onsemi · Diodes write it together as BZX84C5V1.

3. The letters A · B · C — opposite meanings by series

Image description: A customer holds BZX84B5V1 and 1N5231B labels side by side and asks, “Both are B, so the precision is the same, right?” A female clerk makes an X with her fingers and answers, “Even the same B has the opposite meaning!”

1N4728A–1N4761A all end in A, and the Vishay datasheet states for the whole series “Standard Zener voltage tolerance is ± 5 %” (it does not separately explain what the letter A means). Diodes BZT52C · BZX84C, Vishay BZX55 and onsemi MM3Z have no % statement, only min · max voltages in the table.

4. Series defined by number — 1N47xxA · 1N52xxB · MMSZ

The digits in 1N4733A · 1N5231B are serial numbers unrelated to the voltage, so you have to memorize them or check a table. Fortunately, MMSZ52xxB has the same voltage as 1N52xxB with the same ending number (the nominal voltages of the two tables match for every number, and the Vishay 1N5221 datasheet also lists the same numbers: “SOD-123 case with the types designations MMSZ5225 to MMSZ5267”). MMSZ47xx has a test current (IZT) of 50µA and is a Zener for use at very low currents (onsemi “Low IZT”).

5. Package · power by series

The 1N4728A family is often called a “1W Zener”, but the Vishay datasheet lists 1300mW. Power differs by company and mounting condition (board · lead length), so check the datasheet of the company you use.

6. Voltage → part number at a glance

Find the voltage in the row, then pick the part number for the package you want in the column. - means the voltage is not in that series' datasheet table (you can also find a part number with Ctrl+F · find in page).

Only part numbers that appear in each series' datasheet table are included, and ordering suffixes (-7-F · LT1G · T1G, etc.) are omitted. BZX84C follows onsemi (Diodes goes up to 51V), 1N52xxB follows Vishay (onsemi goes up to 1N5252B, with no 1N5224B), and BZX384 · BZX79 use Nexperia notation (hyphen). 1N4762A–1N4764A (82 · 91 · 100V) are not included because they were not in the official documents obtained this time.

7. On-chip marking differs by company

Small SOT-23 · SOD-123 Zeners have only a 2–3 character marking code printed on the chip. Even for the same part number, the marking code differs by company — for example, MMSZ5226B is D1 at onsemi and G1 at Diodes. When finding a part number from a marking code, always check the manufacturer as well.

8. What to check when choosing

• Voltage — the nominal voltage along with min · max (tolerance). Even at the same 5.1V, ±2% and ±5% give different ranges
• Tolerance letter — the meaning of B · C is reversed depending on whether the letter is before the voltage (BZX84) or after the number (1N52xx)
• Test current IZT — VZ in the datasheet is measured at IZT. If the circuit current is very low, use a series with low IZT such as MMSZ47xx
• Power · package — SOT-23 (around 250mW) · SOD-123 (500mW) · DO-41 (1300mW) cannot be swapped for one another and have different thermal margins
• Marking code — when searching by the letters on the chip, use the marking table in the manufacturer's datasheet

Sources: Nexperia BZX84 series (Rev. 7) · BZX79 series (2002) · BZX384 series (Rev. 4), onsemi BZX84C2V4LT1/D (Rev. 23) · MMSZ5221BT1/D (Rev. 17) · MMSZ4678T1/D (Rev. 13) · 1N5221B/D (Rev. 5) · MM3Z2V4ST1/D (Rev. 27), Diodes DS18001 · DS18004 · DS18010, Vishay 85816 (1N4728A) · 85588 (1N5221) · 85604 (BZX55) datasheets. Before actually ordering, check the datasheet of the relevant company.