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National Semiconductor Expands Its Family of Temperature Sensors

August 29, 2006

The patent-pending TruTherm technology, with transistor-mode beta compensation, provides accurate temperature readings for microprocessors developed on 65 nm and 90 nm processes.


SANTA CLARA, CA /PRNewswire-FirstCall/ -- National Semiconductor Corp. introduced a family of high-precision, remote-diode temperature sensors that employ National's TruTherm thermal management technology with transistor-mode beta compensation. These new sensors are designed for applications such as notebook and desktop computers and servers that are powered by high- performance microprocessors manufactured on 65 and 90 nm processes. National pioneered beta compensation technology and was the first to bring it to market, with the introduction of TruTherm technology in the spring of 2005.

TruTherm technology solves the problem of inaccurate remote temperature readings caused by variations in the internal diodes in deep submicron microprocessors, microcontrollers, application-specific integrated circuits and field-programmable gate arrays. Inaccurate remote temperature readings can lead to higher acoustic noise and reduced system performance. National's TruTherm thermal management products improve the accuracy of temperature readings, allowing designers to achieve higher performance and efficiency in their applications, while lowering cooling-fan speed, reducing acoustic noise, and extending system life.

"Thermal management is becoming increasingly important in today's electronics applications, which are growing more complex while also shrinking in size. Accurately monitoring temperature in computing products and complex cores is key to ensuring protection against malfunction or failure due to excessive heat," said Susie Inouye, research director and principal analyst with market research firm Databeans. "Thermal management technology such as National's TruTherm products allows designers to successfully monitor these complex cores that are designed on very small submicron geometries and continue to push the limits of heat dissipation."

About the LM94 Hardware Monitor
The LM94 hardware monitor has a two-wire digital interface compatible with system management bus (SMBus) 2.0. Using a sigma-delta analog-to-digital converter, the LM94 measures the temperature of up to four remote-diode-connected transistors as well as its own die, and up to 16 power supply voltages supporting dual processors. To set fan speed, the LM94 has two pulse-width modulation outputs that are each controlled by up to six temperature zones. The fan-control algorithm can be based on a lookup table, a proportional/integral control loop that supports a temperature-control function, or a combination of both.

The LM94 includes digital filters to smooth temperature readings for better control of fan speed, minimizing acoustical noise. The LM94 has four tachometer inputs to measure fan speed and includes limit and status registers for all measured values. It also supports monitoring of the dynamic power supply voltage for the processor, dual processor thermal throttling monitoring functions, and general-purpose input/output (I/O) pins.

About the Remote-Diode Temperature Sensors

Four-Diode Sensing: LM95234
The LM95234 is an 11-bit digital temperature sensor with a two-wire SMBus interface that monitors the temperature of four remote diodes as well as its own temperature. The LM95234 supports three critical temperature (TCRIT) outputs with individual limits for each channel and masking capability. Two of the LM95234's remote temperature channels have programmable digital filters, while the other two channels use a fault queue to avoid falsely triggering the TCRIT pins if the temperature of a channel momentarily goes above the corresponding limit.

Two-Diode Sensing: LM95241 and LM95233
The LM95241 is a precision, dual remote-diode temperature sensor with a two-wire serial interface compatible with SMBus 2.0. The LM95241 senses three temperature zones, two remote diodes, and its own temperature. It has digital filtering and an advanced input stage that includes analog filtering. The LM95241 resolution format for remote temperature readings can be programmed to be 11-bits signed or unsigned with the digital filtering disabled. When the filtering is enabled, the resolution increases to 13-bits signed or unsigned. In unsigned mode, the LM95241 remote diode readings can resolve temperatures above 127°C. Local temperature readings have a resolution of 9-bits plus sign.

The LM95233 is a two-diode version of the LM95234.

Single-Diode Sensing: LM95235
The LM95235 is an 11-bit digital temperature sensor with a two-wire SMBus interface that monitors the temperature of a single remote diode as well as its own temperature. The LM95235 features programmable TCRIT and OS thresholds and can be used to shut down the system, turn on system fans, or perform a microcontroller interrupt function. The LM95235 is pin compatible with National Semiconductor's industry-standard LM86 and LM89.

Pricing and Availability
Prices for the products start at $1.17 for the LM95241 in 1000-unit quantities. For more information about the products, including how to order samples and evaluation boards, please visit the company's Web site. The LM94 and LM95235 are available now. The LM95233, LM95234, and LM95241 will be available later this fall and are currently sampling.

About National Semiconductor
National Semiconductor creates high-value analog devices and subsystems. National's leading-edge products include power management circuits, display drivers, audio and operational amplifiers, interface products, and data conversion solutions. National's key analog markets include wireless handsets, displays, and a variety of broad electronics markets, including medical, automotive, industrial, and test and measurement applications. Headquartered in Santa Clara, CA, National reported sales of $2.16 billion for fiscal 2006, which ended May 28, 2006. Additional company and product information is available at the company's Web site. TruTherm is a trademark, and National Semiconductor is a registered trademark of National Semiconductor Corp. All other brand or product names are trademarks or registered trademarks of their respective holders.


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