The latest analog-output and digital-output temperature sensors reflect the
current technology trends in this market: higher resolution and higher
precision, lower voltages and smaller package sizes.
As microprocessors move from 90 nanometers to 65 nm, temperature sensor
suppliers like Analog Devices, Andigilog, Maxim Integrated Products, Microchip
Technology, National Semiconductor and Texas Instruments are developing more
accurate devices. These products are designed to help alleviate the temperature
dissipation challenges that PC makers face with their small systems and fast
microprocessors, which generate heat that is difficult to dissipate in small
A digital sensor is an analog sensor with an analog-to-digital (A/D) converter
and the logic needed to communicate with a system. Digital temperature sensors
generally cost more (pricing can range from 30 cents up to $2 each) because of
their higher level of integration and performance. In contrast, analog
temperature sensors usually cost up to 30 cents.
Analog and digital temperature sensors service two different, and very healthy,
market segments. Analog temperature sensors are typically found in
space-constrained applications like cellular handsets, MP3 players, battery
packs, DVDs and industrial instrumentation, where communication over a digital bus is not feasible.
Digital temperature sensors are used in desktop PCs, notebook computers, servers, gaming consoles, digital TVs and displays, where a digital bus is used for communication.
Working with a major cell phone maker, National Semiconductor Corp. (Santa
Clara, Calif.) responded to demands for a low-voltage temperature sensor by
introducing a 1.5-volt analog temperature sensor with user-selectable gains.
Low-power, analog sensors from Microchip Technology Inc. (Chandler, Ariz.) can
be used in place of thermistors, according to the company. The MCP9700 and
MCP9701 temperature sensors come in a small SC-70 package, offer typical power
consumption of 6 amps and cost 30 cents each.
Dual-channel, analog temperature monitor and fan controllers from Maxim
Integrated Products Inc. (Sunnyvale, Calif.) boast 1°C accuracy and provide
thermistor inputs. The combination of high accuracy, dual thermistor inputs and
dual pulse-width modulation fan control makes the MAX6615 and MAX6616 practical
choices for networking equipment, servers and power supplies, according to Maxim.
A single-wire digital output temperature sensor from Texas Instruments Inc. is
said to render high accuracy in a tiny package. The 10-bit-resolution sensor
operates over a temperature range of -40°C to 125°C with typical accuracy of
0.25°C. The devices is capable of measuring temperatures within 2°C accuracy
over a temperature range of -25°C to 85°C and within 3°C over -40°C to 25°C, according to TI’s data sheet.
Andigilog (Tempe, Ariz.) kicked off a family of intelligent thermal-management
solutions with the aSC7511 sensor. The device monitors temperature locally and
remotely using Andigilog's unique temperature-sensing technology to provide
accuracy of ±1°C.
Analog Devices Inc. (Norwood, Mass.) unveiled a complete digital
temperature-monitoring IC, which includes an on-chip temperature sensor that
comes in two performance grades. The ADT75 digital temperature sensor consists
of a bandgap temperature sensor and 12-bit A/D converter. The part monitors and
digitizes the temperature to a resolution of 0.0625°C.