Temperature Sensor Has One Dig
abstract: digital temperature sensors are available with a variety of serial interfaces of varying complexity. this application note shows how to use one family of thermal monitor ics with a very simple 2-wire (clock in, data out) digital interface.
the first digital temperature sensors used the spi bus or i²c bus (also known as smbus) for their serial data outputs. these buses require that the controlling processor write data to the sensor before they can read the temperature data.
the max6629-max6632 reduces complexity by not requiring the processor to write data. it requires only that you drive the clock and chip-select lines, so a simpler burst of clock pulses will read the temperature data.
the circuit of figure 1 makes reading the data simpler still by deriving the chip select signal from the clock. communication is achieved with a single digital input and a single digital output.
clock pulses on the normally high sck line drive active-low cs low, so devices of the max6629-max6632 family let you retrieve digital data by simply applying a burst of clock pulses. (in a normal configuration, the three interface lines active-low cs, so, and sck function as shown in figure 2.) the 2-line approach of figure 1, on the other hand, requires that the sck rest state (quiescent state) be high, which in turn calls for a slight modification of the figure 2 timing diagram.
figure 1. by eliminating the need for a logic line to the active-low cs input, this circuit allows you to simply clock temperature data from the sensor device.
figure 2. a serial-interface timing diagram for the figure 1 temp sensor illustrates the function of active-low cs. it enables the interface when low, then suspends temperature-to-digital conversions until it returns to a level higher than 0.7vcc.
when sck initially goes low, it pulls active-low cs low via the schottky diode d1. you should set the r1-c1 time constant so the active-low cs line rises no higher than 0.3vcc between clock pulses (i.e., 1.5v for a 5v supply in figure 1). an oscilloscope display (figure 3) shows the slow rise time of active-low cs. to allow time for the sensor ic to perform its next temperature-to-digital conversion, active-low cs should remain above 0.7vcc (3.5v in figure 1) for at least 0.5 seconds between temperature-read operations.
figure 3. this scope display from figure 1 shows how the presence of sck pulses (top trace) generates a active-low cs signal (lower trace).
a similar version of this article appeared in the march 4, 2002 issue of electronic design magazine.
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the first digital temperature sensors used the spi bus or i²c bus (also known as smbus) for their serial data outputs. these buses require that the controlling processor write data to the sensor before they can read the temperature data.
the max6629-max6632 reduces complexity by not requiring the processor to write data. it requires only that you drive the clock and chip-select lines, so a simpler burst of clock pulses will read the temperature data.
the circuit of figure 1 makes reading the data simpler still by deriving the chip select signal from the clock. communication is achieved with a single digital input and a single digital output.
clock pulses on the normally high sck line drive active-low cs low, so devices of the max6629-max6632 family let you retrieve digital data by simply applying a burst of clock pulses. (in a normal configuration, the three interface lines active-low cs, so, and sck function as shown in figure 2.) the 2-line approach of figure 1, on the other hand, requires that the sck rest state (quiescent state) be high, which in turn calls for a slight modification of the figure 2 timing diagram.
figure 1. by eliminating the need for a logic line to the active-low cs input, this circuit allows you to simply clock temperature data from the sensor device.
figure 2. a serial-interface timing diagram for the figure 1 temp sensor illustrates the function of active-low cs. it enables the interface when low, then suspends temperature-to-digital conversions until it returns to a level higher than 0.7vcc.
when sck initially goes low, it pulls active-low cs low via the schottky diode d1. you should set the r1-c1 time constant so the active-low cs line rises no higher than 0.3vcc between clock pulses (i.e., 1.5v for a 5v supply in figure 1). an oscilloscope display (figure 3) shows the slow rise time of active-low cs. to allow time for the sensor ic to perform its next temperature-to-digital conversion, active-low cs should remain above 0.7vcc (3.5v in figure 1) for at least 0.5 seconds between temperature-read operations.
figure 3. this scope display from figure 1 shows how the presence of sck pulses (top trace) generates a active-low cs signal (lower trace).
a similar version of this article appeared in the march 4, 2002 issue of electronic design magazine.
session和cookie的区别和联系
AUTOLISP程序设计技巧
集成家庭健康监测
为什么wifi连接上却不能上网
DIY的接地说明
Temperature Sensor Has One Dig
另有13家300mm晶圆厂将在2023年投产
磁珠的作用及特性的详细讲解
狼蛛死亡缠绕鼠标评测 用对鼠标才是王道
基于嵌入式的数控雕刻机控制系统设计
HarmonyOS如何实现跨多终端支持？
物联网怎样将其优越性发挥到极致
1.2MHz ThinSOT升压转换器采用单节电池供电节省电路板空间
对互阻抗放大器的评估（第 1 部分）
三极管的分类、工作原理及功能应用
中芯国际董事会宣布，刘遵义获委任为公司第二类独立非执行董事
韩国计划用5G取代有线网络办公
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创维25NF8800的IC2总线调整的又一法
赛灵思公司宣布在会上展示在光纤网络上的技术领先优势