3 Power Consumption

Another key system requirement is power consumption. On a mechanical relay and a Photorelay device, the main power is consumed by the coil and the LED respectively. The current consumption can vary depending on the device and implementation, but typically 100mW/channel is needed to excite the coil on a mechanical relay. For a Photorelay, the LED typically needs 5mW/channel to fully turn on the switch. On a 4-channel multiplexer, the supply would consume <2.5mW per channel. So, in the 16-channel example shown in Figure 1-1, the mechanical solution would use 1600mW, the Photorelay would use 80mW plus the power consumed by the LED driver, and the multiplexers would use <20mW. Using a multiplexer can dramatically reduce a system’s power needs for portable and low power solutions.