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基于usb总线的温度监测器
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基于usb总线的温度监测器
使用模拟单片机，和LDO，外部热敏电阻，和几个分立器件，可以构造一个高度精确的温度传感应用。
图1中的电路是模拟设备aduc7122精密模拟微控制器可用于精确的热敏电阻温度监测中的应用。的aduc7122集成了多通道12位SAR ADC，十二个12位DAC、一个1.2 V的内部参考，以及一个ARM7内核，126 KB的闪存、8 KB SRAM，以及各种数字外设，如定时器，UART，SPI，I2C接口和两。的aduc7122连接到4.7 KΩ热敏电阻。
Figure 1： ADuC7122 used as a temperature monitor interfaced to a thermistor （simplified schematic， all connections not shown）。
Due to the small form factor of the ADuC7122 （7 mm × 7 mm， 108-ball BGA package） the entire circuit will fit on an extremely small PCB， thus further reducing cost.
Similar in function to an RTD， thermistors are low-cost， temperature-sensitive resistors and are constructed of solid semiconductor materials， which exhibit a positive or negative temperature coefficient. Thermistors are inexpensive and have high sensitivity. They detect small variations in temperature， which could not be observed with an RTD or a thermocouple. However， thermistors are highly nonlinear; thus， they are limited to applications with very narrow temperature ranges if linearization techniques are not applied. Circuit linearization techniques can be accomplished in software.
Despite the powerful ARM7 core and high-speed SAR ADCs， the ADuC7122 still provides a low-power solution. With the ARM7 core running at 326.4 kHz and the primary ADC active and measuring the external temperature sensor， the entire circuit typically consumes 7 mA. Between temperature measurements， the ADC and/or the microcontroller can be switched off to further minimize power consumption.
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