4 Solution Size

An optocoupler works on the principle of converting electrical signal into light and then back into electrical signal to achieve isolation. This limits the choice of dielectric that can be used for insulation to the ones that are optically transparent like air and epoxy. Since the dielectric strengths of air and epoxy are significantly low, they occupy considerable amount of space in a single-channel package, thereby limiting the maximum number of channels that can be fit into a given optocoupler device.

Also, digital isolators use SiO₂ as a dielectric, which has significantly higher dielectric strength and occupies a much lower space to realize a single isolation channel, hence multiple channels can be easily integrated into a small package. A typical single channel optocoupler is usually available in a package size of 3.7 mm × 4.55 mm whereas ISO7762 with SSOP package can fit 6 high-performance channels in a small package area of
4 mm × 5 mm.

Figure 4-1 compares amount of space occupied by eight single-channel optocouplers and four dual-channel optocouplers each with two ISO6741 devices to realize an eight-channel isolation solution. The figure also places ISO7762, six-channel digital isolator, by the side showing the highest channel density achieved in a wide-body SOIC-16 package.