Product Overview
National Semiconductor LM431ACZ Shunt Voltage Reference - TO-92, Script N Marking, Sold Each
Condition
Condition is New: unused new old stock, sold untested. The photographed piece is a black three-lead TO-92 whose face reads the National script N followed by 54DW on the top line, then LM431 and ACZ below it. The three leads are straight and full length, with no bend or clip marks; the upper portion of each lead carries a lighter mottled coating with a distinct line where it ends, and we make no claim about what that coating is. The rounded back of the package is plain except for a molded M in a circle. Stock is 26 pieces from the same holding, so the date and lot line on the piece you receive may not read exactly as the one photographed. No electrical testing has been performed here.
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Product Overview
The LM431ACZ is a three-terminal adjustable shunt voltage reference: set the ratio on an external divider between the reference pin and the cathode, and the device holds the cathode at that programmed voltage by sinking whatever current it has to. National Semiconductor rated the family for an output adjustable up to 36 V, a low dynamic impedance of 0.2 ohms, and sink current from 1.0 mA up to 100 mA, which is why it turns up on the secondary side of so many switching supplies and inside precision regulator and comparator circuits. This one is the TO-92 plastic package, three straight radial leads on the standard through-hole spacing, marked LM431ACZ with the National script N that identifies the maker. Pin function and any voltage or current limit beyond those listed here are not confirmed by us - check the LM431 datasheet for your pinout before you commit a board.
Key Features
- Part number: LM431ACZ, marked on the package face
- Maker: National Semiconductor, script N logo on the package
- Type: adjustable shunt voltage reference and regulator
- Output voltage: adjustable up to 36 V
- Dynamic impedance: 0.2 ohms
- Sink current: 1.0 mA to 100 mA
- Package: TO-92, three straight through-hole leads
- Lot line on the photographed piece: 54DW
- Sold each, 26 pieces on the shelf
Applications
- Repair technician rebuilding the feedback loop on a secondary-side switching supply that used a 431-type reference
- Bench engineer setting a programmable rail on a linear regulator without adding a whole reference module
- Instrument restorer replacing an aged reference on an older National-populated analog board
- Student or hobbyist breadboarding an adjustable shunt reference and wanting a few real parts, not a bag of a hundred
Frequently Asked Questions
What is printed on the part?
Three lines on the flat face: the National script N with 54DW beside it, then LM431, then ACZ. Nothing else is printed on the body, and the rounded back carries only a molded M in a circle.
What output voltage and current will it handle?
The listing carries an output adjustable up to 36 V, dynamic impedance of 0.2 ohms, and sink current of 1.0 mA to 100 mA. Anything beyond that, including tolerance grade and pinout, is not confirmed here - verify against the LM431 datasheet before use.
Has it been tested?
No. We have not powered it up or measured it. What we can tell you is what the camera shows: intact package, legible marking, straight full-length leads with no bend or clip marks.
Will the piece I receive look exactly like the photos?
The package, the part number, and the National script N will match. The date and lot line can vary across the 26 pieces in stock, so treat 54DW as what one piece read, not a guarantee for every piece.
It is sold untested - what am I actually taking on?
You are taking on the electrical unknown and nothing else. The photos are the spec: this is a physically intact TO-92 with legible LM431ACZ marking and straight full-length leads, out of a 26-piece holding of new unused stock, and it goes out as it sits with no bench report behind it. If it does not do what you needed, our satisfaction guarantee stands - that is the trade we are offering, an honest untested part instead of a polished claim we cannot back. Shipping is $8 flat rate and free once the order passes $28, and orders leave our Idaho warehouse the same or next business day.
The script N belongs to a company that no longer exists, but the job this little TO-92 does has not changed: it sits quietly on a divider and tells the rest of the supply what voltage means. Give it a resistor pair and a board that needs an answer, and it goes right back to doing the only thing it ever did.
