DS1985 16 Kbit Add-Only EPROM iButton
16 Kbit non-erasable EPROM for tamper-evident, append-only records.
2 KB of add-only EPROM in sixty-four 256-bit pages: data can be programmed but never erased, and each page can be permanently write-protected. Software can supersede an old page with a newly programmed one, giving append-only ledger behaviour. The right choice for stored-value tokens and audit trails that must not be altered. Shares its die with the DS2505 chip.
A tamper-proof ledger with room to grow
The DS1982 proves a handful of events cannot be edited; the DS1985 does the same across sixty-four pages and 2 KB. That is the difference between a checkpoint stamp and a complete service history — every intervention on a machine, every calibration, every custody transfer, appended in order and physically impossible to erase. Software supersedes an old page by programming a newer one, so the ledger reads forward in time while the original entries stay exactly where they were written.
Key features
- 16 Kbit "add-only" EPROM — data can be appended but never erased, for a tamper-evident audit trail.
- Sixty-four 256-bit pages, each permanently write-protectable; software can supersede an old page.
- Reads parasite-powered at 2.8–6.0 V; programs at 12 V — the write voltage itself deters tampering.
- Family code 0Bh; unique 64-bit ROM; shares its die with the DS2505 chip; ideal for stored-value tokens.
Specifications
| Chip / compatibility | DS1985 · family code 0Bh · chip-form DS2505 |
|---|---|
| Memory | 16 Kbit add-only EPROM (64 pages × 256 bits) |
| Protocol | 1-Wire, 16.3 kbit/s; reads at 2.8–6.0 V, programs at 12 V |
| Package | F3 / F5 can |
| Operating temperature | −40 °C … +85 °C |
Inside the stainless can
A 0.25 mm solid stainless shell, a UV-stable polypropylene grommet isolating lid from base, and the die bonded inside. Lid = data contact, base = ground return.
Which memory iButton do you need?
The whole memory range side by side, grouped by storage technology — capacities and family codes per the Analog Devices datasheets.
| Model | Family code | Capacity | Memory technology | Pick it for |
|---|---|---|---|---|
| DS1971 | 14h | 256 bit + 64-bit OTP | EEPROM — battery-free | Asset tag: a locked ID beside rewritable data |
| DS1972 | 2Dh | 1 Kbit (128 B) | EEPROM — battery-free | Per-page write-protect or EPROM-emulation modes |
| DS1973 | 23h | 4 Kbit (512 B) | EEPROM — battery-free | Largest battery-free memory; production travellers |
| DS1982 | 09h | 1 Kbit (128 B) | EPROM — add-only, cannot be erased | Tamper-evident checkpoints and certificates |
| DS1985 | 0Bh | 16 Kbit (2 KB) | EPROM — add-only, cannot be erased | Full append-only service history |
| DS1992 / DS1993 | 08h / 06h | 1 Kbit / 4 Kbit | NV RAM — battery-backed, unlimited writes | Data that changes constantly on the key |
| DS1996 | 0Ch | 64 Kbit (8 KB) | NV RAM — battery-backed, unlimited writes | Portable database — the largest capacity here |
| DS1994 | 04h | 4 Kbit + RTC | NV RAM + clock, timer, counter, alarms | Time- or usage-limited access that expires by itself |
| DS1904L | 24h | No user memory | Real-time clock only | Give a microcontroller an accurate timebase |
| DS1991 | 02h | 1152 bit = 3 × 384 bit | Secure NV RAM — three password zones | Legacy multi-tenant systems (not for new secure designs) |
| DS1961S | 33h | 1 Kbit + 64-bit secret | EEPROM + SHA-1 challenge–response | The anti-cloning choice — proves it knows a secret |
Ordering information
| MOQ | 100 pcs |
|---|---|
| Lead time | 3–7 days for stock items, 10–15 days for OEM |
| Packing | Bulk ESD bags (100–200 pcs/bag, 2 bags/carton); blister or header cards for retail on request |
| Samples | Free samples for volume buyers — courier at cost |
| Payment | T/T bank transfer; other terms negotiable for repeat orders |
| Shipping | DHL / FedEx / UPS air express; sea or rail freight for pallet volumes |
| Customization | ROM ranges · housing colours · laser logo · private label |
Typical applications
Related products
DS1991 MultiKey iButton
Three password-protected 384-bit subkeys in one button.
DS1992 / DS1993 Memory iButton
1 Kb and 4 Kb NV RAM tokens for carrying data on the key.
DS1996 64 Kb Memory iButton
The large-memory token — 64 Kb of rewritable NV RAM.
DS1961S SHA-1 Authentication iButton
1 Kb EEPROM with on-chip SHA-1 challenge–response.