The ISO7240CF is a quad-channel digital isolator with an input disable function and a selectable high or low failsafe-output function with the CTRL pin (pin 10). The device has logic input and output buffers separated by TI's silicon dioxide (SiO2) isolation barrier. When used in conjunction with isolated power supplies, the device blocks high voltage, isolates grounds, and prevents noise currents from entering the local ground and interfering with or damaging sensitive circuitry. A periodic update pulse is sent across the barrier to ensure the proper dc level of the output. If this dc-refresh pulse is not received for more than 4 s, the input is assumed to be unpowered or not being actively driven, and the failsafe circuit drives the output to the logic state selected by the user. The failsafe-output is a logic high when a logic-high is placed on the CTRL pin or it is left unconnected. If a logic-low signal is applied to the CTRL pin, the failsafe-output becomes a logic-low output state. The ISO7240CF also includes an input disable function that prevents data from being passed across the isolation barrier to the output. When the inputs are disabled, the outputs are set by the CTRL pin. This device may be powered from either 3.3-V or 5-V supplies on either side in any combination. Note that the signal input pins are 5-V tolerant regardless of the voltage supply level being used. The device is characterized for operation over the ambient temperature range of 40C to 125C.