DC/DC Converters

Design

Input and ouput current test

It is always useful to be able to measure input and output current. It is not recommended at all to use standard 0 Ohms shunts.
My advice is to use 1206 or bigger footprint with a trace under. This gives following schematics:
In normal case, test shunt is not populated. When current measure is required, simply cut the PCB trace and use test shunt 1206 pads.

Output L/C filter

Rule of thumb is to select a cut off frequency at 1/10 of the switching regulator frequency.

Multiphase DC/DC

Number of phases : Consider 20A per phase, up to 30A max

Testing

• Load/Line regulation : Dc Vin +/- 5% (12V), check regulator voltage value at min and max load. Max and min value are determined by chips on PCBA
• Check DC In power consumption during spinup phase and stress power consumption and in all sleep modes.
• Power consumption : Check that power consumption of each power rail is within power budget range
• Efficiency at 10%, 50% and 100% load (required >85% over 50% load)
• Ripple : Check that ripple is within other PCBA components range at regulator output under maximum and minimum load
• Dynamic load : Connect a dynamic load, change load from 30% to 100% at 1kHz frequency. Check that ripple stays in the good range
• OCP protection level : Measure OCP protection level. Do the following tests : Power ON -> Short, Short -> Power On. Re power UP. Criteria, converter shall have no damage
• Rise time (no spike)
• Falling time < 10ms (no spike)
• Overshoot and Undershoot : Turn On and Off each DC/DC converter. Check that over and undershoot is in other PCBA components range
• Output voltage on product temperature range : 0°C and 40°C with product burnin
• Check Power ON and power off sequence trough all product sleep modes / and power on
• Cold Start : DC/DC converters starts at 0°C