The ISO7240, ISO7241 and ISO7242 are quad-channel digital isolators with multiple channel configurations and output enable functions. These devices have logic input and output buffers separated by TI’s silicon dioxide (SiO2) isolation barrier. Used in conjunction with isolated power supplies, these devices block high voltage, isolate grounds, and prevent noise currents from entering the local ground and interfering with or damaging sensitive circuitry. The ISO7240 has all four channels in the same direction while the ISO7241 has three channels the same direction and one channel in opposition. The ISO7242 has two channels in each direction. The A and C option devices have TTL input thresholds and a noise-filter at the input that prevents transient pulses from being passed to the output of the device. The M option devices have CMOS Vcc/2 input thresholds and do not have the input noise-filter or the additional propagation delay. 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, the input is assumed to be unpowered or not being actively driven, and the failsafe circuit drives the output to a logic high state. (Contact TI for a logic low failsafe option). These devices may be powered from either 3.3-V or 5-V supplies on either side in any 3.3-V / 3.3-V, 5-V / 5-V, 5-V / 3.3-V, or 3.3-V / 5-V combination. Note that the signal input pins are 5-V tolerant regardless of the voltage supply level being used. These devices are characterized for operation over the ambient temperature range of –40°C to 125°C.