PCB layout
The PCB was laid out to fit the 10x10cm shape that’s so economical to produce at the Chinese prototype houses. The NXA66 sits on the left with a direct, wide path along top and bottom ground fills from the current return terminal to the ground entry point. Further optimisation could be made here by ignoring the return ground terminals and wiring from the front panel ground directly back to the power entry ground at the back.
Indicator LEDs and switchgear terminals are placed at the front and power entry is at the back. I will place a 2.1mm panel-mount connector on the back of the case as well as an on-off switch.
The 3-pin fan and temperature connectors surround a rectangular cutout in the PCB. The cutout is designed for routing the wires from the sensor and fan below the board for aesthetic reasons.
The regulator output runs through top and bottom polygons to the sense resistor where it unavoidably shrinks to pass through the component whereafter it expands to a pair of polygons connected to dual output terminals. The INA226 is placed as close as possible to the sense resistor.
I mentioned earlier that the TI Simple Switcher regulators are an easy to use design, and they are, but good practice is still in order when laying out the components that take part in the switching loop.
TI’s application note AN-1229 covers it all but the basics are that the switching components should be placed as close to the regulator as possible (tricky with through hole), they should be arranged in the order shown in the schematic and the ground returns for each of them should be tied together and terminated to a ground plane at the ground pin of the IC. Hopefully you can see how I’ve done that in the above image.
