DS1972 1 Kbit EEPROM iButton
Rewritable 1 Kbit EEPROM with per-page write-protect — no battery.
1024 bits of EEPROM in four 256-bit pages, written through an 8-byte scratchpad for verified transfers. Each page can be permanently write-protected or put in EPROM-emulation ("write-to-0") mode to help guard against accidental erasure or tampering. Battery-free — it draws power from the 1-Wire line. Shares its die with the DS2431 chip.
Ordering information
| MOQ | Confirmed by model and order when quoting |
|---|---|
| Preparation time | Availability and lead time are confirmed by model and order when quoting |
| Packing | Confirm pack quantity, protection and labelling for the selected model. |
| Samples | Sample quantity, fees and shipping are confirmed for the selected model. |
| Payment | Agree payment terms and the payee in the quotation and invoice. |
| Shipping | Confirm the shipping method, cost and timing for your destination and order. |
| Customization | State ROM, colour, marking and packing needs; feasibility and cost require confirmation. |
Choose page by page: rewritable, locked, or write-once
Its four pages are not all-or-nothing. Each 256-bit page can be left freely rewritable, permanently write-protected, or switched into EPROM-emulation mode where bits can only be cleared, never set back — three different behaviours inside one battery-free button. That lets a single device hold a locked configuration block, an append-only usage counter and a rewritable status field at the same time, which neither the plain-EEPROM DS1973 nor the fully add-only DS1982 can do.
Key features
- Original DS1972 reference: 1,024-bit EEPROM arranged as four 256-bit pages.
- Original-device writes use an 8-byte scratchpad; each page can be write-protected or set to EPROM emulation.
- Confirm the host’s page configuration and write sequence, then verify readback before committing irreversible page settings.
Specifications
| Chip / compatibility | DS1972 · family code 2Dh · chip-form DS2431 |
|---|---|
| Memory | 1 Kbit EEPROM (4 pages × 256 bits) + 8-byte scratchpad |
| Protocol | 1-Wire, 16.3 kbit/s (Overdrive ~125 kbit/s) |
| Package | F3 / F5 can |
| Operating temperature | −40 to +85 °C; 2.8–5.25 V — per the original manufacturer's datasheet; confirm for the supplied version |
| Options | Colour, marking and other customization options: feasibility, MOQ and cost are confirmed in the quote. |
Product dimensions
Inside the stainless can
Typical construction of this can format: a stainless-steel shell, an insulating grommet separating lid from base, and the chip bonded inside. Lid = data contact, base = ground return. Wall thickness, grommet material and other construction details: confirm for the supplied version.
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 | Battery-free rewritable memory (4 Kbit); production travellers |
| DS1982 | 09h | 1 Kbit (128 B) | EPROM — add-only; written data is not erasable (per datasheet) | Add-only records such as checkpoints and certificates |
| DS1985 | 0Bh | 16 Kbit (2 KB) | EPROM — add-only; written data is not erasable (per datasheet) | Append-only service history (16 Kbit) |
| DS1992 / DS1993 | 08h / 06h | 1 Kbit / 4 Kbit | NV RAM — battery-backed, high write endurance (per datasheet) | Data that changes constantly on the key |
| DS1996 | 0Ch | 64 Kbit (8 KB) | NV RAM — battery-backed, high write endurance (per datasheet) | Portable database — 64 Kbit NV RAM |
| DS1994 | 04h | 4 Kbit + RTC | NV RAM + clock, timer, counter, alarms | Time- or usage-limited access with the expiry held in the key |
| DS1904L | 24h | No user memory | Real-time clock only | Give a microcontroller a real-time 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 | Authentication: proves it knows a secret (assess cloning risk for your own system) |
Typical applications
Frequently asked questions
What does “per-page write-protect or EPROM-emulation” mean in practice?
Each of the four 256-bit pages can independently stay rewritable, be locked forever, or switch to a mode where bits can only be cleared — so one device can hold a locked config block, an append-only counter and a rewritable status field at the same time.
How durable is the memory?
Per the original manufacturer's datasheet: 200,000 write cycles at +25 °C and 40-year retention at +85 °C, with Overdrive communication up to 125 kbit/s, and Level-4 ESD protection (±8 kV contact, ±15 kV air-gap) for harsh electrical environments. Confirm all figures for the supplied version.
Is it the same chip as the DS2431?
Per the original manufacturer's datasheets the two are closely related: the DS1972 is the iButton form (stainless F3/F5 can) of the DS2431 family device, so host software written for one is expected to work with the other. Confirm for the supplied version and test a sample.
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.