Temperature sensor delivers multi-point sensing, high accuracy

Dallas, Tex. — Dallas Semiconductor, a wholly owned subsidiary of Maxim
Integrated Products, has introduced the DS28EA00, a 1-wire digital temperature
sensor with ±0.5°C accuracy and a new chain-mode signaling and protocol feature that automatically determines the physical location of individual sensors in an
environment where multiple sensors are connected to a common 1-wire line.

The DS28EA00 is suitable for applications that require accurate multi-point digital temperature measurements with minimal wiring complexity and cost. Typical applications include rack-based equipment such as wireless base stations, central office switches, enterprise servers, HVAC, and process monitoring.

Available in an 8-pin microSOP package, the DS28EA00 measures temperature over the -40°C to 85°C range and is factory calibrated in a liquid bath to provide a worst-case conversion error of ±0.5° within the ambient-measurement-temperature range of -10°C to 85°; it provides a ±2.0°C worst-case conversion error within the ambient range of -40° to -10°. Device temperature sensing and digitization is produced from the differential VBE output of a matched-NPN transistor pair and a 1st-order sigma-delta ADC. Conversion resolution is user programmable with 9-bit to 12-bit options.

The DS28EA00 operates over the Dallas Semiconductor 1-wire interface with a protocol
that delivers power as well as communication over a single connection. This unique interface enables multiple 1-wire devices, including the DS28EA00, to be multi-dropped on the line and operate independently. With power and communication over a single contact, the DS28EA00 minimizes wiring complexity and associated cost in a multi-device system, said the company.

Like all 1-wire devices, the DS28EA00 has a unique 64-bit internal serial
number that is used in a multi-drop environment to select a specific device for temperature results. Said to be the first of its kind to determine the physical location of multiple temperature sensors, the DS28EA00 includes a chain-mode command set and two signal pins for daisy-chaining multi-dropped devices. A 1-Wire host controller then uses the chain-mode command protocol to learn the 64-bit serial number of each part in the chain, starting with the first device on the line and proceeding sequentially.

This sequence knowledge is directly linked to the physical location of the DS28EA00 in the system. In addition, the two chain-mode daisy-chain signal pins perform a dual-purpose. They can be used to detect the physical location of a device in a network, or they can be used as a 5 V/4 mA GPIO to control LED indicators or other input/output signaling.

Prices: Starts at $2.27 (1,000-up, FOB USA)

Dallas Semiconductor Corp. , 1-972-371-4000,

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