Isolated 6-Channel Output Module

Untested! This circuit isolates up to six buttons or switches. The isolated DC-DC converter provides up to 200mA at 4.8V to the switch circuit. The switches are connected between SW and SWGND. There are 0805 pads for 100nF debouncing capacitors (closest to the chip on the top side), as well as for 100kOhm pull-up resistors (on the top side); these may be optional. On the underside, there are 0805 pads for 10kOhm current-limiting resistors. The two 0805 pads on the topside are for two 100nF decoupling capacitors. The 1206 pad on the topside marked 250 is for a 250 Ohm resistor, to dissipate 20mA (0.1W = 1/10W) to ensure stable operation of the isolated DC-DC converter. The two 0805 pads on the bottom side marked 4.7u and 10u are for 4.7uF and 10uF decoupling capacitors, respectively, for the isolated DC-DC converter. The board is about 31mm × 28mm, and has three 3mm mounting holes. Multiple boards can be connected in parallel (their 4.8V, SW1..SW6, and SWGND in parallel), to provide the switch states to multiple microcontrollers, but keeping the microcontrollers isolated from each other (and the button circuit).