Part # Technical Article Automotive LM2901H LM2904WH LM2903H TS922H Std-Linear - High Temperature TA0311 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: High Temperature Electronics


Part Details:

TA0311 TECHNICAL ARTICLE High Temperature Electronics 1 Introduction In the semiconductor world, there are numerousproducts specified with an industrial temperaturerange (-40/+85°C), and somewhat fewer with anautomotive temperature range (-40/+125°C). It is much more difficult to find products specifiedand guaranteed for temperature above +125°C. However, since applications requiring hightemperature components are growing, thedemand for "hot" silicon devices has increasedtremendously. One of the leading markets concerned here isautomotive, which continues to show a relativelygood growth rate despite economic crisis. New IGBT Driver 2 Why the need for high-temperature semiconductors? Automotive and industrial environments are responsible for most high temperature requirements. In thesesegments, for instance, sensors and electronics have to be placed right near to their function modules.This is done to limit the use of high-cost, high-end wiring needed to avoid interference effects. All expertsknow that long wires are much more sensitive to EMI point and to control this, costly wiring that offersinterference-immunity must be used. Placing the semiconductor next to the module it controls reducesthe need for such wiring. However, the environment for semiconductors can be very harsh in the Automotive and Industrialsegments. Typical examples are the electronics used in the ECU (Engine Control Unit) which monitorsand optimizes an automotive engine. This unit is increasingly found in the engine compartment wheretemperature variations are extreme. Figure 1 Engine control unit in Automotive segment ... Sensors Engine And / Or Control ... Unit Modules ... Long Costly Low immunity Wires Shielded wires to Interferences Must be used TA0311/June 2004 Revision 1 1/5 TA0311 Technical Article Example of a typical application: An electronic module (ECU, Engine cooling fan, automatic gearbox...) is adjusted directly in the enginecompartment and is usually thermally connected to the engine cooling water or engine oil circuit. Because of this, ambient temperatures for the electronic control unit are in the range of 125°C. The powerdissipation of the semiconductor components results in a further increase of temperature in the ECU ofaround 10°C. This means that every semiconductor device is subject to an ambient temperature of about135°C. On top of this, the power dissipation of each component has to be added, resulting in themaximum temperature of the silicon. In the example below, the standard operational amplifier orcomparator has to operate at around 140°C. Therefore a device is required that is specified for and guarantees operation for at least 140°C. Figure 2 T Engine Compartment : 125°C amb T Control Unit : 125°C + 10°C amb T Electronic Device : 125°C + 10°C + 5°C j 3 High temperature silicon: a great challenge At elevated temperatures, semiconductors are affected by physical laws which can modify of theirelectrical properties. In addition to a transistor s reduction in gain with increasing temperature, designersface problems caused by a phenomenon called leakage current. The degree to which leakage currentpresents an important problem can vary depending on the technologies used and the designoptimization, but it is always present at elevated temperatures. For example, there is lower leakagecurrent in gallium arsenide (GaAs) technologies, versus silicon (Si) technologies, but silicon devices aremuch more common and widely used. The basic operating principle of semiconductors is the management of energy. At the atomic scale, thereare two different levels of energy for the electrons: the valence level and the conduction level. Theseparation between the two energy bands is called the band gap, often specified as the parameter Eg.The value of Eg is large for an insulator but very small (or zero) for metals, which are known to be goodconductors. In semiconductors, when electrons have enough energy (through thermal excitation, forinstance) to move from the valence band to the conduction band, the conductivity of the inner materialincreases. In the case of a silicon-based semiconductor, the band gap energy decreases as thetemperature increases. Thus, at elevated temperature, electrons can move easier from the valence bandto the conduction band creating what we call leakage current. 2/5


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Technical Article Automotive LM2901H LM2904WH LM2903H TS922H Std-Linear - High Temperature TA0311.pdf Datasheet