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Temp sensors suit 65nm, 90nm processors

Posted: 31 Aug 2006 ?? ?Print Version ?Bookmark and Share

Keywords:National? TruTherm? temperature sensor? thermal management? transistor-mode beta compensation?

National Semiconductor Corp. has introduced a family of high-precision, remote-diode temperature sensors that employ the company's TruTherm thermal management technology with transistor-mode beta compensation. The company said these new sensors are specifically designed for applications such as notebook and desktop computers and servers that are powered by high-performance microprocessors manufactured on 65nm and 90nm processes.

National said it pioneered beta compensation technology and was the first to bring it to market with the introduction of TruTherm technology in 2005. According to the company, TruTherm technology solves the problem of inaccurate remote temperature readings caused by variations in the internal diodes in deep sub-micron microprocessors, microcontrollers, ASICs and FPGAs. Inaccurate remote temperature readings can lead to higher acoustic noise and reduced system performance. TruTherm products improve the accuracy of temperature readings, the company said, 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," said Susie Inouye, research director and principal analyst with Databeans. "Accurately monitoring temperature in computing products and complex cores is key to ensuring protection against malfunction or failure due to excessive heat."

LM94 Hardware Monitor
The LM94 hardware monitor has a two-wire digital interface that is compatible with SMBus 2.0. Using a sigma-delta ADC, the device 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 PWM 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 (PI) control loop that supports a temperature control (Tcontrol) function, or a combination of both.

The LM94 includes digital filters to smooth temperature readings for better control of fan speed, minimizing acoustical noise. It 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 (VccP), dual processor thermal throttling monitoring (PROCHOT) functions and general purpose I/O pins.

Remote-diode temperature sensors
The LM95234 is an 11bit digital temperature sensor with a two-wire SMBus interface that monitors the temperature of four remote diodes as well as its own temperature. The device supports three critical temperature (TCRIT) outputs with individual limits for each channel and masking capability. Two of the its 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.

The LM95241 is a precision, dual remote-diode temperature sensor with a two-wire serial interface that is 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 11bits signed or unsigned with the digital filtering disabled. When the filtering is enabled, the resolution increases to 13bits signed or unsigned. In unsigned mode, its remote diode readings can resolve temperatures above 127C. Local temperature readings have a resolution of 9bits plus sign. The LM95233 is a two-diode version of the LM95234.

The LM95235 is an 11bit 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 device features programmable TCRIT and OS thresholds, and can be used to shut down the system, turn on system fans or as a microcontroller interrupt function. The LM95235 is pin-compatible with the company's industry-standard LM86 and LM89.

Prices start at $1.17 for the LM95241 in 1,000-unit quantities. The LM94 and LM95235 are available today. The LM95233, LM95234 and LM95241 will be available next quarter and are currently sampling.

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