Characteristics of a Long Duration Noise Induced on a Wearable Devices by Potential Drop of a Charged Proximity Object Caused by ESD

In an actual situation where wearable devices are used, there is a situation where the device is charged along with a human body to high voltage, and their potential rapidly drops when electrostatic discharge (ESD) from the human body to a surrounding object occurs. In this situation, our previous studies observed that a long-duration induced noise with exponential decay in the order of tens to hundreds of microseconds under the condition that the input circuit of the device had high impedance. In this study, we measured the fundamental characteristics of the long-duration induced noise by varying conditions, such as that with/without a case of the circuit, the case’s material, and the circuit’s structure, using a simple verification circuit consisting of only an $R C$ circuit and plates. As a result, we found that a long-duration induced noise with a large amplitude is induced when the electric field from the charging plate couples imbalance to the GND or HOT side of the circuit. It was also found that the amplitude of the long-duration induced noise became smaller due to the cancellation of the electrostatic induction when the electrical field couples to both the GND and HOT sides. These results support our hypothesis of the inducing mechanism of the long-duration noise.