DS1990R-F5

DS1990R-F5 iButton (presence-pulse variant)

R-variant; the original manufacturer's datasheet describes a presence pulse on contact with a live bus.

Electrically similar to the DS1990A — a 64-bit read-only ROM with family code 01h. The documented difference is behavioural: per the original manufacturer's datasheet, the DS1990R gives a presence pulse on contact (after power-on reset) when the button touches an already-powered 1-Wire bus, so a reader can detect the key at the moment it lands. Consider it where presence-on-contact detection matters; confirm the behaviour for the supplied version and test a sample on your own reader.

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.

Key features

Original DS1990R reference: a 64-bit serial-number iButton with presence signalling after power-on reset.
The original datasheet specifies that the post-reset presence pulse is guaranteed by design, not production tested; bus and contact conditions still matter.
For a DS1990A replacement, compare electrical limits, package fit and the controller’s detection sequence with the supplied sample.

Specifications

Chip / compatibility	DS1990R format · family code 01h
Memory	64-bit ROM, read-only (8-bit family + 48-bit serial + 8-bit CRC)
Package	F5 can
Protocol	1-Wire, 16.3 kbit/s
Operating temperature	−40 °C … +85 °C (1-Wire chip, per the original manufacturer's datasheet; confirm for the supplied version)

Inside the stainless can

Typical F5 can: Ø16.25 × 5.89 mm · typical F3 can: Ø16.25 × 3.10 mm

Original DS1990A layout reference: 8-bit family code + 48-bit serial + 8-bit CRC

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.

Typical applications

Access Control Guard Tour & Patrol Checkpoints

Frequently asked questions

What does the “R” in DS1990R actually change?

Behaviour, not data: per the original manufacturer's datasheet, the DS1990R gives a presence pulse on contact (after power-on reset) when the button touches an already-powered 1-Wire bus, so the reader can detect the key the instant it lands. The datasheet describes this as guaranteed by design, not production tested; confirm for the supplied version. ROM format and family code 01h are the same as the DS1990A.

Are DS1990A and DS1990R interchangeable?

On paper, for reading — per the original manufacturer's datasheets both use the same 64-bit read-only ROM format. Whether your reader and controller treat them alike must be confirmed: test a sample on your own system before ordering. Specify the R only where the system depends on presence-on-contact detection.

Which systems require the R variant?

Installations that depend on presence-on-contact detection — for example fast gates, turnstiles and controllers that poll briefly and need to catch the key on the first landing rather than a re-present. Whether that is needed on your system depends on your controller and firmware; test a sample on your own system before ordering.