Permanent Read-Only iButton Key Tag — Factory-Burned UID, Zero Battery, 10-Year Life
For access control integrators and fleet telematics operators who issue one iButton key tag per person and need that key to stay locked for life.
Every TM1990A-F5 iButton key tag leaves the fab with its identity permanently set. The 64-bit ROM ID — an 8-bit family code, a 48-bit serial, and an 8-bit CRC — is laser-written into the silicon during production and will not change for any reader, any programmer, or any weather condition over a decade or more of daily use. This is the credential you order when a tenant key stays with apartment A-12 for half a decade, a driver badge belongs to one employee for their entire tenure, or a building checkpoint is bolted to a wall once and never re-tagged.
The hardware inside is deliberately minimal: a 16.25 mm F5 stainless disc crimped into a 40 mm ABS handle. No battery. No capacitor. No moving part. The silicon die draws parasitic power from the 1-Wire data line the instant the disc face touches a chrome probe — the reader supplies both voltage and the clock reference. The UID is clocked out in under five milliseconds at overdrive speed. The assembly reads at −40°C in a Siberian garage, at +75°C on a Dubai parking gate, and through snow, mud, and thick work gloves that would defeat any optical or fingerprint scanner.
Because the UID is immutable, this particular access token solves one problem that a writable credential cannot: zero risk of a departing employee or tenant tampering with their iButton key tag to match a new valid UID. In a read-only chip, the identity is physically burned — it cannot be erased, reprogrammed, or spoofed by any handheld tool in the field. The security model is not “trust the software lock” but “the hardware itself refuses to change.” For a multi-building residential portfolio, a corporate campus with high turnover, or a fleet where driver assignment is audited monthly, this distinction matters at scale.
This iButton Key Tag vs the Writable Version — Know the Difference
Confused between the TM1990A-F5 iButton key tag and the RW1990? The distinction boils down to one question: does the credential ever need to be re-assigned to a different person?
| TM1990A-F5 (this page) | RW1990 (writable) | |
|---|---|---|
| UID behaviour | Permanent. Fab-burned. Cannot be altered. | Re-programmable via TM handheld tool |
| Who buys it | Property managers, fleet ops, factory HR — one person, one fob, done | Locksmiths, rotating-tenant landlords — monthly re-issue cycle |
| Security model | Hardware immutability — the chip itself refuses to change. No software lock needed. | Write-lock flag — the programmer writes then locks. Lock can sometimes be factory-reset. |
| Unit lifecycle | Fixed assignment. Key is de-authorised in software when the person leaves, not re-written. | Rotating assignment. UID is overwritten on the same piece of hardware when a new tenant arrives. |
If your deployment reads the UID once, stores it in an access panel database, and never needs to physically change the chip — this is the correct product. If every new tenant means a site visit with a programmer in hand — see the RW1990 page instead.
Three Deployments Where the iButton Key Tag Works
Residential door access at scale
A residential integrator in Warsaw codes TM1990A-F5 tokens by handle colour: green for Block A, red for Block B, blue for maintenance staff. An Iron Logic Matrix-II panel at each lobby entrance reads the factory UID on first touch, checks it against the authorised list, and opens or denies within a few hundred milliseconds. The panel logs every entry attempt by UID and timestamp — a property manager with 12 buildings can audit access across the entire portfolio from one screen.
When a tenant moves out, the manager de-authorises the old UID in the panel database — ten seconds of software work. A new fob from spare stock gets registered to the apartment and handed to the incoming tenant. The departed tenant still holds a physical token, but it opens nothing. No re-programming tool on-site. No risk of the former tenant cloning a valid key. This workflow is why almost every residential integrator we supply defaults to this credential over the writable alternative for permanent tenant assignments.
Driver identification at engine start
A Teltonika FMB120 telematics terminal in a 200-truck fleet carries a 1-Wire probe reader mounted on the dashboard, within arm’s reach of the driver’s seat. Each driver clips a colour-coded TM1990A-F5 paddle to their personal key ring — blue for day shift, red for night — and touches it to the chrome disc at the start of every shift.
The FMB120 captures the 64-bit UID, timestamps the ignition event to the millisecond, and streams the data over the cellular network to the fleet back-end — Wialon, Navixy, or Traccar, depending on which platform the fleet operator uses. The fleet manager now has a per-vehicle, per-driver, per-shift audit trail: who drove unit 47, for how long, at what speed, inside or outside the geofence. Driver performance, fuel consumption, and overtime hours are automatically attributed to the correct individual without manual log sheets or dashboard PIN entry that can be shared.
The TM1990A-F5 wins here because one driver keeps the same fob for years. The credential lives on a key ring, goes home at night, and returns to the dashboard the next morning. No battery to degrade in summer cabin heat. No RFID field to interfere with the truck’s CAN bus. No risk of two drivers swapping fobs to game the system — the UID is permanently locked to one person, and a colour mismatch is spotted at a glance.
Employee attendance clocking
A factory in Shenzhen with 800 workers on three shifts deploys ZKTeco inBio terminals at six entrances. Every employee touches a TM1990A-F5 paddle to clock in and out. The burned UID cannot be cloned by a late-arriving colleague trying to clock in for someone else. No fingerprint hygiene issue common in chemical or food-handling factories. No PIN sharing. No face-recognition failures under a mask or safety goggles. The ABS handle carries a silk-print logo and a laser-etched employee number — corporate-lobby professional, factory-floor durable. After three years of daily use, the MicroCan still reads at 100% on the same reader it was paired with on day one.
Compatible Reader Families — What This Fob Plugs Into
Because the TM1990A-F5 speaks the Dallas/Maxim 1-Wire protocol at both 15 kbps (standard) and 142 kbps (overdrive), it works with any reader that has a 1-Wire bus — a dedicated iButton probe port or a Wiegand-to-1-Wire converter board. The table below covers the readers that integrators most frequently pair with this access token.
| Reader | Where it is installed |
|---|---|
| Iron Logic Matrix-II EH / K | Apartment lobbies, gated communities across CIS |
| Bolid S2000-Proxy | Commercial offices, industrial gatehouses |
| Rubezh R3-Reader-1W | Budget residential blocks, small offices |
| ZKTeco inBio / Anviz C2 | HR attendance terminals worldwide |
| Teltonika FMB120 / FMB640 | Vehicle dashboards — fleet telematics |
| Ruptela FM-Pro4 | Driver authentication in EU-regulated fleets |
| Generic panel-mount chrome probe | Custom panels, OEM vending machines, coffee dispensers |
When NOT to Buy This Product
Honesty saves both sides time. Do not order the TM1990A-F5 if:
- You re-issue credentials monthly. A student dorm, a co-working space, a locksmith who clones keys on-site — these need a re-writable chip. The TM1990A-F5 burns every unit as a single-use identity; rotating tenants means buying fresh batches instead of re-using hardware.
- You need to store data on the fob. This chip carries a 64-bit ROM and nothing else. No user memory, no stored-value counter, no transaction log. If the fob needs a prepaid balance or an equipment service record, you need an EEPROM-equipped chip.
- Your reader lacks a 1-Wire port. If the access panel only accepts Wiegand or RS-485 with no converter board budgeted, this fob will not plug in. Check the reader spec before ordering.
iButton Key Tag Technical Specifications
| Parameter | Value |
|---|---|
| Chip | TM1990A-F5 (DS1990A-compatible), 64-bit ROM, Manchester encoding |
| MicroCan | F5 stainless steel, Ø 16.25 ±0.05 mm, height 5.89 ±0.10 mm |
| Handle | Virgin ABS, injection-moulded, 40 mm paddle |
| Weight | ~8 g per unit |
| Read method | Touch-contact, parasitic-powered — no battery, no RF field |
| Read speed | < 5 ms at 142 kbps overdrive |
| Operating temp | −40°C to +75°C |
| Ingress protection | IP64 (splash-proof; overmoulded IP67 version on request) |
| Service life | > 10 years or > 1,000,000 touches |
| Handle colours | Black, blue, red, yellow, green, white, grey; custom Pantone |
| Custom marking | Laser-etched serial + silk-print logo on one or both faces |
| Packing | 100 pcs / inner box; 5,000 pcs / carton (73 × 24 × 33 cm, 25 kg) |
| Monthly capacity | > 2,000,000 pcs across five in-house production lines |
Quality Control — What Happens Before the Carton Is Sealed
Every outbound batch passes a five-stage outgoing inspection on a random 100-unit sample. MicroCan geometry is caliper-checked against the F5 tolerance window. All 100 units are read at 15 kbps and 142 kbps overdrive — a single failure triggers a full batch re-test. UIDs are scanned for duplicates against the last five production lots. The ABS handle is visually inspected for parting-line burr, sink mark, flash, ring-hole alignment, silk-print offset, and colour drift (3% reject threshold). Twenty units are drop-tested from 1.5 metres onto concrete — any crack triggers a root-cause investigation. The full QC report ships with the cartons.
Frequently Asked Questions
Can this fob be re-programmed or overwritten?
No. The 64-bit UID is fab-burned and permanent. That is the security feature — an access token that cannot be tampered with by any handheld tool, any software, or any environmental reset. If your deployment needs re-writable UIDs for on-site cloning or monthly tenant rotation, the RW1990 is the correct product.
Does it contain a battery?
No. The silicon die steals power from the 1-Wire data line at the instant the disc touches the probe — the reader supplies both the operating voltage and the clock reference. There is no battery, no capacitor, and no active component inside the assembly. This is why the fob is rated for over ten years of daily use with zero field maintenance.
Will it read through a glove or ice?
Yes, within reason. The metal disc must contact the probe, but a thin layer of frost, dirt, or a fabric glove does not block 1-Wire conduction. This is a contact bus, not an RF field — it tolerates conditions that defeat RFID. Caked mud or a thick leather gauntlet may require wiping the disc first.
Is the TM1990A-F5 a genuine Maxim DS1990A part?
It is a fully compatible functional equivalent — same 1-Wire Manchester protocol, same F5 MicroCan geometry, same electrical characteristics at both standard and overdrive speeds. The silicon is produced under a licensed compatible design in a separate fabrication facility, which is why it carries the TM prefix rather than DS. Over 340 B2B deployments supplied since 2023 report zero field-compatibility issues with any 1-Wire reader on the market.
What colours, logos, and serial numbers can I put on the handle?
Seven stock ABS colours — black, blue, red, yellow, green, white, grey — with custom Pantone matching available (adds 7–10 days to the standard lead time). A single-colour silk-print logo on one or both paddle faces. A unique laser-etched serial number on every unit, traceable to its production lot. We require a physical print sample to be signed off before mass production — a digital mock-up is useful for discussion but not for final approval.
What is the minimum order?
Free samples (10–50 mixed units) ship within three business days to verified company addresses. Pilot order: 500 units at standard tier pricing. Production-scale orders: 1,000 units and above. We do not inflate the first-order MOQ because the pilot phase is how both sides confirm the right chip, the right colour allocation, and the right lot discipline before scaling to project volume.
How long from purchase order to delivery?
Fourteen to twenty-one days for stocked colours. Custom Pantone and laser marking add seven to ten working days. Orders of 10,000+ units require twenty-five to thirty-five days. Chinese New Year in January–February adds thirty to forty days regardless of volume — plan accordingly.
What if a batch arrives with units that do not read?
Replacements ship at supplier cost within thirty days of delivery, supported by the batch QC report that accompanied the original shipment. This is standard B2B practice and should be expected from any production-grade supplier. If a supplier cannot provide a QC report with the cartons, the batch should not be released for field installation.
Request a Free Sample Kit
Tell us your deployment scenario, your reader model, and the approximate quantity. We ship a 10-unit sample kit — mixed handle colours, one impedance-matched chrome probe reader — within three business days to any verified company address.
Email: [email protected] | WhatsApp: +852 5989 6589 | WeChat: 147891664
