We present the electrical and radiation characterisation of the most recent prototype of the bPOL12V DCDC converter, a stacked assembly of two ASICs inside a QFN32 package. The use of a reference voltage generator chip in 130nm CMOS on top of the ASIC integrating the control system and power train enables improved radiation tolerance and the trimming of the output voltage during the production phase. Prototype samples have been exposed to X-rays, proton and neutron irradiations, as well as subject to long-term electrical stress to evaluate their reliability in the application. The results confirm that only a few minor modifications are required to achieve production readiness.