1-Wire Digital Temperature Sensor Provides New Chain-Mode Function for Determination of Physical Location
DALLAS, TX—February 12, 2007—Dallas Semiconductor, a wholly owned subsidiary of Maxim Integrated Products (NASDAQ: MXIM), introduces the DS28EA00, a 1-Wire® digital temperature sensor with ±0.5°C accuracy and a new chain-mode signaling and protocol feature that quickly and 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 ideal for applications that require accurate multipoint digital temperature measurements with minimal wiring complexity and cost.
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°C within the ambient-measurement-temperature range of -10°C to +85°C; it provides ±2.0°C worst-case conversion error within the ambient range of -40°C to -10°C. 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 multidropped on the line and operated independently. With power and communication over a single contact, the DS28EA00 minimizes wiring complexity and associated cost in a multidevice system. Like all 1-Wire devices, the DS28EA00 has a unique 64-bit internal serial number that is used in a multidrop environment to select a specific device for temperature results. The first of its kind to be able to determine the physical location of multiple temperature sensors, the DS28EA00 includes a chain-mode command set and two signal pins for daisy-chaining multidropped 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. Additionally, the two chain-mode daisy-chain signal pins are dual-purpose—they can be used to detect the physical location of a device in a network, or they can be used as a 5V/4mA GPIO to control LED indicators or other input/output signaling.
Typical applications for the DS28EA00 include rack-based equipment such as wireless base stations, central office switches, enterprise servers, HVAC, and process monitoring where accurate multipoint temperature sensing is important for system reliability. The temperature sensor is available in an 8-pin µSOP package. Prices start at $2.27 (1,000-up, FOB USA).
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