Abstract: The components shown enable this temperature-to-period converter (IC1) to interface with standard industrial logic levels, while operating on a -48V telecomm systems bus. The circuit presented features the MAX6576 digital temperature sensor. Integrated-circuit temperature sensors are generally preferred in data-acquisition systems for which the accuracy demands are not extreme. Sensor, signal-processing, and data-conversion electronics, plus an easy-to-use digital-I/O interface are all integrated in the temperature sensor IC, and all at low cost. Such ICs require a supply voltage in the range +3V to +5V, negative to common, and they usually draw very low supply current. Biasing the sensor is more difficult in a telecomm system, however, where the only supply voltage available is usually the -48V systems bus. If no other positive low-voltage supply is available, the design must normally include a DC-DC converter powered from -48V. The circuit of Figure 1 solves the above problem without needing an extra power supply. This circuit allows the IC sensor to operate from -48V. With the addition of a few components, it also serves as an interface to the digital inputs of programmable-logic controllers (PLCs) or other digital I/O that require logic signals ranging from 0V to some positive level. As shown here, the output can sink up to 1.6mA, and swing from 0V to about +40V (the maximum VCE for a 2N3904 transistor). That capability meets the requirements for digital I/O in most industrial systems (+15 or +5V). Figure 1. The components shown enable this temperature-to-period converter (IC1) to interface with standard industrial logic levels while operating on a -48V telecomm systems bus. The circuit in Figure 1 includes an absolute temperature-to-period converter (IC1). Connected as shown, it provides a conversion constant of 640µs/°K. (At room temperature the period is about 190ms, giving a frequency of 5.2Hz.) This scheme can also accommodate similar sensors, such as temperature-to-frequency converters. For a listing of accuracy specifications and other parameters associated with IC1, please see the MAX6576 data sheet. This design idea appeared in the February 16, 2006 issue of ED. 相关型号   APP 3872: Jul 25, 2006 MAX6576 SOT温度传感器，周期时间/频率输出 完整的数据资料 (PDF, 152kB) 免费样品 自动更新 需要自动接收最新发布的应用笔记吗？请订阅EE-Mail™ (English only)。 我们期待您的反馈！ 喜欢？不喜欢？有待改善？或为我们提供建议？请与我们联系 — 我们将根据您的意见或建议改善我们的工作。 网页评价或提供建议   下载，PDF格式 (27kB)  AN3872, AN 3872, APP3872, Appnote3872, Appnote 3872