In an I2C circuit, every component in the system is exposed to some level of electrical noise. Sometimes electrical noise can become large enough to unintentionally influence the voltage levels on floating pins of I2C devices. This high noise level can have a negative impact on the operation of a device, especially if the pin that is left floating is the device reset pin. If the reset pin of an I2C device is left floating, electrical noise can cause the device to unintentionally enter a reset state. To avoid unintentionally entering a reset state, bias the reset pin of all I2C target devices to a defined logic level with either a pullup or pulldown resistor. Biasing the reset pin keeps the reset pin in a defined state until the pin is intentionally changed by a controller. If high level of noise is expected in the circuit, a capacitor can be added onto the reset pin to further help reduce the effect of noise. Generally, 1-μF and 0.1-μF capacitors are both used for this type of application.

If the reset pin of an I2C target device is active low, use a pullup resistor to bias the reset pin to V_CC. In this configuration, the device is only reset if the device is intentionally driven low by a controller. If the reset pin of an I2C target device is active high, use a pulldown resistor to bias the target device to GND. In this configuration, the device is only reset if the device is intentionally driven high by a controller.