Operating temperature

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An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range (which part; TJ usually) which varies based on the device function and application context, and ranges from the minimum operating temperature to the maximum operating temperature (or peak operating temperature). Outside this range of safe operating temperatures the device may fail.

Temperature physical property of matter that quantitatively expresses the common notions of hot and cold

Temperature is a physical quantity expressing hot and cold. It is measured with a thermometer calibrated in one or more temperature scales. The most commonly used scales are the Celsius scale, Fahrenheit scale, and Kelvin scale. The kelvin is the unit of temperature in the International System of Units (SI), in which temperature is one of the seven fundamental base quantities. The Kelvin scale is widely used in science and technology.

Contents

It is one component of reliability engineering.

Similarly, biological systems have a viable temperature range, which might be referred to as an "operating temperature".

Ranges

Most devices are manufactured in several temperature grades. Broadly accepted grades [1] [2] are:

Nevertheless, each manufacturer defines its own temperature grades so designers must pay close attention to actual datasheet specifications. For example, Altera uses five temperature grades for its products: [3]

Datasheet Technical document summarizing performance and constraints of system components

A datasheet, data sheet, or spec sheet is a document that summarizes the performance and other technical characteristics of a product, machine, component, material, a subsystem or software in sufficient detail that allows design engineer to understand the role of the component in the overall system. Typically, a datasheet is created by the manufacturer and begins with an introductory page describing the rest of the document, followed by listings of specific characteristics, with further information on the connectivity of the devices. In cases where there is relevant source code to include, it is usually attached near the end of the document or separated into another file.

Altera company

Altera Corporation was a leading American manufacturer of programmable logic devices (PLDs), reconfigurable complex digital circuits, from 1984 through 2015. Altera released its first PLD in 1984.

The use of such grades ensures that a device is suitable for its application, and will withstand the environmental conditions in which it is used. Normal operating temperature ranges are affected by several factors, such as the power dissipation of the device. [4] These factors are used to define a "threshold temperature" of a device, i.e. its maximum normal operating temperature, and a maximum operating temperature beyond which the device will no longer function. Between these two temperatures, the device will operate at a non-peak level. [5] For instance, a resistor may have a threshold temperature of 70 °C and a maximum temperature of 155 °C, between which it exhibits a thermal derating. [4]

Resistor Passive electrical component providing electrical resistance

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat, may be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements, or as sensing devices for heat, light, humidity, force, or chemical activity.

In electronics, derating is the operation of a device at less than its rated maximum capability in order to prolong its life. Typical examples include operation below the maximum power rating, current rating, or voltage rating.

For electrical devices, the operating temperature may be the junction temperature (TJ) of the semiconductor in the device. The junction temperature is affected by the ambient temperature, and for integrated circuits, is given by the equation: [6]

Junction temperature, short for transistor junction temperature, is the highest operating temperature of the actual semiconductor in an electronic device. In operation, it is higher than case temperature and the temperature of the part's exterior. The difference is equal to the amount of heat transferred from the junction to case multiplied by the junction-to-case thermal resistance.

A semiconductor material has an electrical conductivity value falling between that of a conductor, such as metallic copper, and an insulator, such as glass. Its resistance decreases as its temperature increases, which is behaviour opposite to that of a metal. Its conducting properties may be altered in useful ways by the deliberate, controlled introduction of impurities ("doping") into the crystal structure. Where two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers which include electrons, ions and electron holes at these junctions is the basis of diodes, transistors and all modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits and others. Silicon is a critical element for fabricating most electronic circuits.

Integrated circuit electronic circuit manufactured by lithography; set of electronic circuits on one small flat piece (or "chip") of semiconductor material, normally silicon

An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material that is normally silicon. The integration of large numbers of tiny transistors into a small chip results in circuits that are orders of magnitude smaller, faster, and less expensive than those constructed of discrete electronic components. The IC's mass production capability, reliability, and building-block approach to circuit design has ensured the rapid adoption of standardized ICs in place of designs using discrete transistors. ICs are now used in virtually all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other digital home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs.

in which TJ is the junction temperature in °C, Ta is the ambient temperature in °C, PD is the power dissipation of the integrated circuit in W, and Rja is the junction to ambient thermal resistance in °C/W.

The watt is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer. In dimensional analysis, power is described by .

Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance.

Aerospace and military

Electrical and mechanical devices used in military and aerospace applications may need to endure greater environmental variability, including temperature range.

In the United States Department of Defense has defined the United States Military Standard for all products used by the United States Armed Forces. A product's environmental design and test limits to the conditions that it will undergo throughout its service life are specified in MIL-STD-810, the Department of Defense Test Method Standard for Environmental Engineering Considerations and Laboratory Tests. [7]

The MIL-STD-810G standard specifies that the "operating temperature stabilization is attained when the temperature of the functioning part(s) of the test item considered to have the longest thermal lag is changing at a rate of no more than 2.0 °C (3.6 °F) per hour." [7] It also specifies procedures to assess the performance of materials to extreme temperature loads. [8]

Military engine turbine blades experience two significant deformation stresses during normal service, creep and thermal fatigue. [9] Creep life of a material is "highly dependent on operating temperature", [9] and creep analysis is thus an important part of design validation. Some of the effects of creep and thermal fatigue may be mitigated by integrating cooling systems into the device's design, reducing the peak temperature experienced by the metal. [9]

Commercial and retail

Commercial and retail products are manufactured to less stringent requirements than those for military and aerospace applications. For example, microprocessors produced by Intel Corporation are manufactured to three grades: commercial, industrial and extended. [10]

Because some devices generate heat during operation, they may require thermal management to ensure they are within their specified operating temperature range; specifically, that they are operating at or below the maximum operating temperature of the device. [11] Cooling a microprocessor mounted in a typical commercial or retail configuration requires "a heatsink properly mounted to the processor, and effective airflow through the system chassis". [11] Systems are designed to protect the processor from unusual operating conditions, such as "higher than normal ambient air temperatures or failure of a system thermal management component (such as a system fan)", [11] though in "a properly designed system, this feature should never become active". [11] Cooling and other thermal management techniques may affect performance and noise level. [11] Noise mitigation strategies may be required in residential applications to ensure that the noise level does not become uncomfortable.

Battery service life and efficacy is affected by operating temperature. [12] Efficacy is determined by comparing the service life achieved by the battery as a percentage of its service life achieved at 20 °C versus temperature. Ohmic load and operating temperature often jointly determine a battery's discharge rate. [13] Moreover, if the expected operating temperature for a primary battery deviates from the typical 10 °C to 25 °C range, then operating temperature "will often have an influence on the type of battery selected for the application". [14] Energy reclamation from partially depleted lithium sulfur dioxide battery has been shown to improve when "appropriately increasing the battery operating temperature". [15]

Biology

Mammals attempt to maintain a comfortable body temperature under various conditions by thermoregulation, part of mammalian homeostasis. The lowest normal temperature of a mammal, the basal body temperature, is achieved during sleep. In women, it is affected by ovulation, causing a biphasic pattern which may be used as a component of fertility awareness.

In humans, the hypothalamus regulates metabolism, and hence the basal metabolic rate. Amongst its functions is the regulation of body temperature. The core body temperature is also one of the classic phase markers for measuring the timing of an individual's Circadian rhythm. [16]

Changes to the normal human body temperature may result in discomfort. The most common such change is a fever, a temporary elevation of the body's thermoregulatory set-point, typically by about 1–2 °C (1.8–3.6 °F). Hyperthermia is an acute condition caused by the body absorbing more heat than it can dissipate, whereas hypothermia is a condition in which the body's core temperature drops below that required for normal metabolism, and which is caused by the body's inability to replenish the heat that is being lost to the environment. [17]

Notes

  1. http://www.ti.com%2Flit%2Fan%2Fspra953c%2Fspra953c.pdf&usg=AOvVaw3APC_MT12EUr3i-G3oKy0R
  2. http://www.analog.com%2Fen%2Ftechnical-articles%2Fdata-sheet-intricacies-absolute-maximum-ratings-and-thermal-resistances.html&usg=AOvVaw1YD6OGZro4noj3OzLvrgWL
  3. Altera Corporation.
  4. 1 2 Analog Devices.
  5. Analog Devices, Power dissipation.
  6. Vassighi & Sachdev 2006, p. 32.
  7. 1 2 United States Department of Defense.
  8. United States Department of Defense, section 2.1.1.
  9. 1 2 3 Branco, Ritchie & Sklenička 1996.
  10. Pentium Processor Packing Identification CodesIntel's packaging indicates the processors operating temperature range by denoting it with a grade: 'Q' (commercial grade), 'I' (industrial grade), and 'L' or 'T' (extended grade). It also has an automotive grade 'A'
  11. 1 2 3 4 5 Intel Corporation.
  12. Crompton 2000.
  13. Crompton 2000, p. figure 30.33.
  14. Crompton 2000, p. 2/5, section 2.1.
  15. Dougal, Gao & Jiang 2005.
  16. Benloucif et al. 2005.
  17. Marx 2010, p. 1870.

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