Embedded Lab

Andy Brown explored reverse engineering the ARTESYN NXA66 regulator module to build a cost-effective bench-power supply with high current supply capability. NXA66 is a non-isolated dc-dc converter targeted at computing applications that require precise voltage and fast transient requirements of today’s high performance applications such as workstations, file servers, desktop computers, telecommunications equipment, adapter cards, DSP and data processing. He designed an Atmega328 driven controller board that would host the NXA66 and expose its functionality via a front panel consisting of seven segment display modules.

High current capacity power supply board

I’ve included a relay between the 12V input and the NXA66 because I don’t want the module powering up by itself without being co-ordinated by my controller. I discovered during experimentation that the module goes into an undefined state if you attempt to switch between the two available voltage levels while the power is on and for that reason I want to be able to set the control pins to the desired state and then power up the module. If the user decides to switch voltages while power is on then I’ll programmatically cut the power, set the VSP pin accordingly and then power up the module. A power MOSFET could be used equally well for this switching purpose; I tossed a virtual coin and it came down on the side of the relay.
All the functionality of the module is exposed to the controller. The slot itself is a 2×25 card edge connector with a 2.54mm pitch and an inter-row spacing of 5.08mm. The VSP and OUTEN pins are switched by MOSFETs and linked directly to LEDs that show their current state. Artesyn hint at a requirement for an output capacitor in their datasheet so I include a 150µF electrolytic at the output terminal. The output and return terminals themselves are doubled up to provide a higher current carrying capacity.