Low Noise Power Distribution Board

Introduction

In many high performance applications there is a need for low noise, high current power rails of many voltages for different subsystems.  In total, we require around 250W of power supplied by our low voltage battery system of 5, 12, and 24V rails.  Our low voltage battery system ranges from around 14-17v, so a set of buck/boost converters are appropriate.

Technical Details

In our case, we choose buck/boost ICs with very high switching frequency and excellent EMI performace: the LTM4613, LTM8064, and LTM8054.  These devices are all-in-one solutions, containing the switching FETs internally and only require a handful of external components to set output voltages and provide decoupling.  We also supply an external clock to further increase performance for our high current application.  These devices support master/slave configuration to boost output capiblity, which is needed for our 12V rail. 

These devices are available in a ball grid array (BGA) package.  This requires that the devices are mounted using a reflow oven, as it would be impossible to solder them by hand.  They also require additional cooling in the form of external heatsinks.  Care must be taken to route these components correctly during layout, as improper layout will increase EMI due to reduce loop area and change of loop area during switching.

To save cost, we've routed the board on two layers and elect to use 2oz copper.  Resist is stripped from our power traces in order to increase their thermal performance.  We also include some extra circuitry for indication of battery and output voltage presence, using an opamp comparator.   

These devices will be a chalange to assemble properly and will test our PCB assembly capibilities.  They've also been chalanging during design, as mistakes requiring us to desolder BGA packages would require us to reball the ICs, a process which requires extra tools.  

Additional Information

Additional information on the packages used can be found on Analog Device's website, along with a wide selection of other buck/boost regulators for different applications.  

You can find additional information about our pod and the Hyperloop competition at https://www.michiganhyperloop.com/ or our instagram, @michiganhyperloop.