温度传感器芯片简化设计(英文翻译)

1、 外文翻译温度传感器芯片简化设计当你开始选择一个温度传感器,你不再局限于一个模拟输出或数字输出设备。现在有一个广泛的传感器类型的选择,其中一个应该匹配您的系统的需求。直到最近,所有市场上的温度传感器提供的模拟输出。热敏电阻、RTDs和热电偶是紧随其后的是另一个模拟输出设备,硅温度传感器。在大多数应用程序中,不幸的是,这些模拟输出设备需要一个比较器,ADC,或者一个放大器的输出,使它们有用。因此,当更高级别的集成成为可行的,温度传感器与数字接口。这些集成电路在各种形式的销售,从简单的设备,信号当一个特定的温度已经超过了那些报告远程和本地的温度,同时提供警告在程序温度设置。选择现在模拟输出和数字输

2、出传感器之间不是简单的;有一个广泛的传感器类型的选择。温度传感器的种类四个温度传感器类型如图1所示。理想的模拟传感器提供了一个输出电压,是一个完美的线性温度的函数(a)。在数字I / O类传感器(B),温度数据在多个0和1的形式传递给单片机,通常通过一个串行总线。沿着相同的总线,数据被发送到单片机的温度传感器,通常设定的温度极限预警销的数字输出将旅行。警报打断了单片机温度极限时已经超过了。这种类型的设备还可以提供风扇控制。“模拟正量”传感器(C)可与各种类型的数字输出。集成电路的输出电压与温度曲线的数字输出开关,当一个特定的温度已经超过了。在这种情况下,“+”添加到模拟温度传感器无非是一个比较

3、器和一个参考电压。其他类型的“+”部分船温度数据的延迟时间后被选通,一部分频率的形式或方波的周期,这将在稍后讨论。系统监控(D)是最复杂的集成电路的四个。除了提供的功能数字I / O型,这种类型的设备一般监控系统提供电压,提供一个警报当电压上升高于或低于限制通过I / O总线。风机监测和/或控制有时是包含在这种类型的IC。在某些情况下,这类设备是用于确定风扇是否工作。更复杂的版本控制风机作为一个或多个测量温度的函数。系统监控传感器没有这里讨论但简要提到给完整可用的类型的温度传感器。模拟输出温度传感器热敏电阻和硅温度传感器广泛应用形式的模拟输出温度传感器。图2中清楚地表明,当电压和温度之间的线性

4、关系是必要的,一个硅比热敏电阻温度传感器是一个更好的选择。然而,在一个狭窄的温度范围,热敏电阻可以提供合理的线性和良好的灵敏度。许多电路最初由热敏电阻随时间更新使用硅温度传感器。硅温度传感器有不同的输出尺度和偏移量。一些,例如,可用与产出成正比的转移函数K,其他人C或F。C的一些部分提供一个偏移量,负温度可以使用单端供应监控。在大多数应用程序中,这些设备的输出输入比较器或a / D转换器的温度数据转换成数字格式。尽管需要这些额外的设备、热敏电阻和硅温度传感器继续享受流行由于低成本和方便的使用在许多情况下。数字 I/O 温度传感器大约五年前,介绍了一种新型的温度传感器。这些设备包括一个数字接口,

5、允许与单片机通信。接口通常是一个我C或SMBus串行总线,但其他串行接口SPI等是常见的。除了报告单片机温度读数,接口也从单片机接收指令。这些指令通常温度限制,如果超过,激活一个数字信号的温度传感器集成电路单片机中断。单片机可以调整风扇转速或后退一个微处理器的速度,例如,控制温度。 这种类型的设备是可用的各种特性,其中,远程温度传感。使遥感,大多数高性能cpu包含一个芯片上的晶体管,它提供了一个模拟电压的温度。(只有一个晶体管的使用两个pn结。)图3显示了一个远程被监视CPU使用这种技术。其他应用程序利用离散晶体管来执行相同的功能。另一个重要功能上找到这些类型的传感器(包括传感器如图3所示)是

6、能够中断时单片机测量温度超出范围有界高和低的限制。在其他传感器,产生一个中断,当测量温度超过温度高或低的阈值(即。,而不是两个)。对传感器在图3中,这些限制被传输到温度传感器通过SMBus界面。如果温度高于或低于限制范围内移动,警报信号中断处理器。见图4是一个类似的设备。监控一个pn结,然而,它监控四个交叉点,其内部的温度。因为箴言MAX1668消耗少量的权力,其内部温度接近环境温度。测量环境温度指示是否系统风机正常运行。控制风扇,而远程温度监控的主要功能是集成电路如图5所示。这一部分的用户可以选择两种不同的模式之间的风扇控制。在PWM模式下,单片机控制风扇转速作为测量温度的函数通过改变的责任

7、周期信号发送到风扇。这允许的功耗远小于线性模式的控制,这也提供了一部分。因为一些球迷发出可听见的声音的频率PWM信号控制,线性模式可以是有利的,但在价格更高的功耗和额外的电路。增加功耗的一小部分力量被整个系统,。该集成电路提供警报信号中断时,单片机温度违反指定的限制。安全特性信号的形式称为“公开”(“温度”的缩写版本)。如果微控制器或软件锁定而温度上升到危险水平,警报信号将不再是有用的。然而,公开,积极一旦通过SMBus温度高于水平集,通常用于没有援助的单片机控制电路。因此,在这个高温场景中与单片机功能,明显的可以用来直接关闭系统电源,单片机,并防止潜在的灾难性的失败。这类数字I / O设备的

8、广泛使用在服务器、电池和硬盘驱动器。温度监控在许多地方增加服务器的可靠性:在主板(本质上是底盘内的环境温度),在CPU死,等其他发热组件图形加速器和硬盘驱动器。电池将温度传感器由于安全原因和优化充电概要文件,电池寿命最大化。有两个很好的理由,监测温度的一个硬盘驱动器,这主要取决于主轴电机的速度和环境温度:读取错误驱动增加在极端温度,和硬盘的MTBF是通过温度控制明显改善。通过测量系统内的温度,你可以控制电动机转速优化可靠性和性能。开车还可以关闭。在高端系统,可以生成警报系统管理员来指示温度极端或数据丢失的情况下是可能的。模拟正温度感应器“模拟正量”传感器通常适合简单的测量的应用。这些集成电路生

9、成逻辑输出的测量温度和区别于数字I / O传感器主要是因为他们在一行输出数据,而不是一个串行总线。模拟正量传感器的简单实例,旅行当温度超过特定的逻辑输出。其中一些设备跳闸温度高于预设阈值时,其他人,当温度低于一个阈值。这些传感器允许温度阈值调整电阻,而其他人则固定阈值。图6所示的设备购买与特定的内部温度阈值。电路说明常见的三种使用这种类型的设备:提供一个警告,关闭设备,或打开一个风扇。 当实际温度读数需要,单片机,传感器,传输阅读在一行可能是有用的。单片机的内部计数器测量时间,这种类型的温度传感器的信号很容易转换为测量温度。图7中的传感器输出的方波频率在开尔文环境温度成正比。图8中的设备是相似

10、的,但方波的周期在k环境温度成正比。图9中,一个真正新颖的方法,允许多达八个温度传感器连接在这个共同的线。从这些传感器提取温度数据的过程开始时,单片机的I / O端口同时闪光灯所有线路上的传感器。然后迅速重新配置单片机作为输入,以接收来自每个传感器的数据。数据编码为传感器后,每时每刻的时间选通。每个传感器编码后这段时间选通脉冲在一个特定的时间范围。碰撞避免分配每个传感器自己允许的时间范围。通过该方法准确性高得惊人:0.8C是典型的在室温下,精确匹配的集成电路编码形式的温度数据传输的频率方波。也是一样的装置,利用方波的周期。这些设备在有限电路中是优秀的应用程序。例如,当从单片机温度传感器必须隔离

11、,成本控制在最低,因为只有一个光隔离器是必要的。这些传感器也很大的效用在汽车和暖通空调的应用程序,因为他们减少铜运行的距离。预期的温度传感器发展集成电路温度传感器提供一系列不同的功能和接口。随着这些设备继续发展,系统设计者将看到更多特定于应用程序的特性以及连接传感器系统的新方法。最后,芯片设计者的能力整合更多的电子产品在同一模区域确保温度传感器将很快包括新功能和特殊接口。Temperature Sensor ICs Simplify DesignsWhen you set out to select a temperature sensor, you are no longer limited

12、 to either an analog output or a digital output device. There is now a broad selection of sensor types, one of which should match your systems needs. Until recently, all the temperature sensors on the market provided analog outputs. Thermistors, RTDs, and thermocouples were followed by another analo

13、g-output device, the silicon temperature sensor. In most applications, unfortunately, these analog-output devices require a comparator, an ADC, or an amplifier at their output to make them useful. Thus, when higher levels of integration became feasible, temperature sensors with digital interfaces be

14、came available. These ICs are sold in a variety of forms, from simple devices that signal when a specific temperature has been exceeded to those that report both remote and local temperatures while providing warnings at programmed temperature settings. The choice now isnt simply between analog-outpu

15、t and digital-output sensors; there is a broad range of sensor types from which to choose. Classes of Temperature SensorsFour temperature-sensor types are illustrated in Figure 1. An ideal analog sensor provides an output voltage that is a perfectly linear function of temperature (A). In the digital

16、 I/O class of sensor (B), temperature data in the form of multiple 1s and 0s are passed to the microcontroller, often via a serial bus. Along the same bus, data are sent to the temperature sensor from the microcontroller, usually to set the temperature limit at which the alert pins digital output wi

17、ll trip. Alert interrupts the microcontroller when the temperature limit has been exceeded. This type of device can also provide fan control. Figure 1. Sensor and IC manufacturers currently offer four classes of temperature sensors. Analog-plus sensors (C) are available with various types of digital

18、 outputs. The VOUT versus temperature curve is for an IC whose digital output switches when a specific temperature has been exceeded. In this case, the plus added to the analog temperature sensor is nothing more than a comparator and a voltage reference. Other types of plus parts ship temperature da

19、ta in the form of the delay time after the part has been strobed, or in the form of the frequency or the period of a square wave, which will be discussed later. The system monitor (D) is the most complex IC of the four. In addition to the functions provided by the digital I/O type, this type of devi

20、ce commonly monitors the system supply voltages, providing an alarm when voltages rise above or sink below limits set via the I/O bus. Fan monitoring and/or control is sometimes included in this type of IC. In some cases, this class of device is used to determine whether or not a fan is working. Mor

21、e complex versions control the fan as a function of one or more measured temperatures. The system monitor sensor is not discussed here but is briefly mentioned to give a complete picture of the types of temperature sensors available. Analog-Output Temperature SensorsThermistors and silicon temperatu

22、re sensors are widely used forms of analog-output temperature sensors. Figure 2 clearly shows that when a linear relationship between voltage and temperature is needed, a silicon temperature sensor is a far better choice than a thermistor. Over a narrow temperature range, however, thermistors can pr

23、ovide reasonable linearity and good sensitivity. Many circuits originally constructed with thermistors have over time been updated using silicon temperature sensors. Figure 2. The linearity of thermistors and silicon temperature sensors, two popular analog-output temperature detectors, is contrasted

24、 sharply. Silicon temperature sensors come with different output scales and offsets. Some, for example, are available with output transfer functions that are proportional to K, others to C or F. Some of the C parts provide an offset so that negative temperatures can be monitored using a single-ended

25、 supply. In most applications, the output of these devices is fed into a comparator or an A/D converter to convert the temperature data into a digital format. Despite the need for these additional devices, thermistors and silicon temperature sensors continue to enjoy popularity due to low cost and c

26、onvenience of use in many situations. Digital I/O Temperature SensorsAbout five years ago, a new type of temperature sensor was introduced. These devices include a digital interface that permits communication with a microcontroller. The interface is usually an IC or SMBus serial bus, but other seria

27、l interfaces such as SPI are common. In addition to reporting temperature readings to the microcontroller, the interface also receives instructions from the microcontroller. Those instructions are often temperature limits, which, if exceeded, activate a digital signal on the temperature sensor IC th

28、at interrupts the microcontroller. The microcontroller is then able to adjust fan speed or back off the speed of a microprocessor, for example, to keep temperature under control. This type of device is available with a wide variety of features, among them, remote temperature sensing. To enable remot

29、e sensing, most high-performance CPUs include an on-chip transistor that provides a voltage analog of the temperature. (Only one of the transistors two p-n junctions is used.) Figure 3 shows a remote CPU being monitored using this technique. Other applications utilize a discrete transistor to perfor

30、m the same function. Figure 3. A user-programmable temperature sensor monitors the temperature of a remote CPUs on-chip p-n junction. Another important feature found on some of these types of sensors (including the sensor shown in Figure 3) is the ability to interrupt a microcontroller when the meas

31、ured temperature falls outside a range bounded by high and low limits. On other sensors, an interrupt is generated when the measured temperature exceeds either a high or a low temperature threshold (i.e., not both). For the sensor in Figure 3, those limits are transmitted to the temperature sensor v

32、ia the SMBus interface. If the temperature moves above or below the circumscribed range, the alert signal interrupts the processor. Pictured in Figure 4 is a similar device. Instead of monitoring one p-n junction, however, it monitors four junctions and its own internal temperature. Because Maxims M

33、AX1668 consumes a small amount of power, its internal temperature is close to the ambient temperature. Measuring the ambient temperature gives an indication as to whether or not the system fan is operating properly.Figure 4. A user-programmable temperature sensor monitors its own local temperature a

34、nd the temperatures of four remote p-n junctions. Controlling a fan while monitoring remote temperature is the chief function of the IC shown in Figure 5. Users of this part can choose between two different modes of fan control. In the PWM mode, the microcontroller controls the fan speed as a functi

35、on of the measured temperature by changing the duty cycle of the signal sent to the fan. This permits the power consumption to be far less than that of the linear mode of control that this part also provides. Because some fans emit an audible sound at the frequency of the PWM signal controlling it,

36、the linear mode can be advantageous, but at the price of higher power consumption and additional circuitry. The added power consumption is a small fraction of the power consumed by the entire system, though.Figure 5. A fan controller/temperature sensor IC uses either a PWM- or linear-mode control sc

37、heme. This IC provides the alert signal that interrupts the microcontroller when the temperature violates specified limits. A safety feature in the form of the signal called overt (an abbreviated version of over temperature) is also provided. If the microcontroller or the software were to lock up wh

38、ile temperature is rising to a dangerous level, the alert signal would no longer be useful. However, overt, which goes active once the temperature rises above a level set via the SMBus, is typically used to control circuitry without the aid of the microcontroller. Thus, in this high-temperature scen

39、ario with the microcontroller not functioning, overt could be used to shut down the system power supplies directly, without the microcontroller, and prevent a potentially catastrophic failure. This digital I/O class of devices finds widespread use in servers, battery packs, and hard-disk drives. Tem

40、perature is monitored in numerous locations to increase a servers reliability: at the motherboard (which is essentially the ambient temperature inside the chassis), inside the CPU die, and at other heat-generating components such as graphics accelerators and hard-disk drives. Battery packs incorpora

41、te temperature sensors for safety reasons and to optimize charging profiles, which maximizes battery life. There are two good reasons for monitoring the temperature of a hard-disk drive, which depends primarily on the speed of the spindle motor and the ambient temperature: The read errors in a drive

42、 increase at temperature extremes, and a hard disks MTBF is improved significantly through temperature control. By measuring the temperature within the system, you can control motor speed to optimize reliability and performance. The drive can also be shut down. In high-end systems, alerts can be gen

43、erated for the system administrator to indicate temperature extremes or situations where data loss is possible. Analog-Plus Temperature Sensors Analog-plus sensors are generally suited to simpler measurement applications. These ICs generate a logic output derived from the measured temperature and ar

44、e distinguished from digital I/O sensors primarily because they output data on a single line, as opposed to a serial bus. In the simplest instance of an analog-plus sensor, the logic output trips when a specific temperature is exceeded. Some of these devices are tripped when temperature rises above

45、a preset threshold, others, when temperature drops below a threshold. Some of these sensors allow the temperature threshold to be adjusted with a resistor, whereas others have fixed thresholds. The devices shown in Figure 6 are purchased with a specific internal temperature threshold. The three circ

46、uits illustrate common uses for this type of device: providing a warning, shutting down a piece of equipment, or turning on a fan.Figure 6. ICs that signal when a temperature has been exceeded are well suited for over/undertemperature alarms and simple on/off fan control. When an actual temperature

47、reading is needed, and a microcontroller is available, sensors that transmit the reading on a single line can be useful. With the microcontrollers internal counter measuring time, the signals from this type of temperature sensor are readily transformed to a measure of temperature. The sensor in Figu

48、re 7 outputs a square wave whose frequency is proportional to the ambient temperature in Kelvin. The device in Figure 8 is similar, but the period of the square wave is proportional to the ambient temperature in kelvins.Figure 7. A temperature sensor that transmits a square wave whose frequency is p

49、roportional to the measured temperature in Kelvin forms part of a heater controller circuit.Figure 8. This temperature sensor transmits a square wave whose period is proportional to the measured temperature in Kelvin. Because only a single line is needed to send temperature information, just a singl

50、e optoisolator is required to isolate the signal path. Figure 9, a truly novel approach, allows up to eight temperature sensors to be connected on this common line. The process of extracting temperature data from these sensors begins when the microcontrollers I/O port strobes all the sensors on the line si