ISO72x and ISO72xx Digital Isolators

Texas Instruments' ISO721, ISO721M, ISO722, and ISO722M are digital isolators with a logic input and output buffer separated by a silicon dioxide (SiO2) insulation barrier. This barrier provides galvanic isolation of up to 400V.

The ISO7220 and ISO7221 are dual-channel digital isolators. To facilitate PCB layout, the channels are oriented in the same direction in the ISO7220 and in opposite directions in the ISO7221. These devices have a logic input and output buffer that is separated by TI’s silicon dioxide (SiO2) isolation barrier, which provides galvanic isolation of up to 4000V. Tri-channel and quad-channel digital isolators are also available.

Overview

Used in conjunction with isolated power supplies, these devices prevent noise currents on a data bus or other circuits from entering the local ground and interfering with or damaging sensitive circuitry.

A binary input signal is conditioned, translated to a balanced signal, and then differentiated by the capacitive isolation barrier. Across the isolation barrier, a differential comparator receives the logic transition information, then sets or resets a flip-flop and the output circuit accordingly.