8.2.1.1.2 Fixed Threshold Voltages

The window comparator thresholds cannot be changed on-the-fly since these are set by hardware (typically with a resistive ladder). This may add a limitation if the user wants to change the comparator thresholds during operation without switching in a new resistor ladder.

Many applications in the field of preventive maintenance, building automation, and Internet of Things (IoT) require a sensor monitor which operates autonomously and gives an alert/interrupt to the host MCU only when the sensor output crosses a predefined, programmable threshold. Typically battery-operated, wireless sensor nodes like smoke detectors, temperature monitors, ambient light sensors, proximity sensors and gas sensors fall under this category. The ADS7142 is an excellent fit for such sensor monitoring systems due to its ability to autonomously monitor sensor output and wake up the host controller whenever the sensor output crosses pre-defined thresholds. Additionally, the ADS7142 has an internal data buffer which can store 16 sample data which the user can read if further analysis is required. Figure 113 shows typical block diagram of ADS7142 as sensor monitor. As is shown in Figure 113, the sensor can be connected directly to the input of the ADC (depending on the sensor output signal characteristics).

Figure 113. Sensor Monitor Circuit with ADS7142