A self-cancellation DC-DC Buck converter (SC-Buck) with 97% output voltage accuracy for biomedical implant device in 28nm CMOS process

An implantable medical device, such as cardiac pacemakers system is generally used to detect irregular heartbeats and correct it. For a none-error and long-term usage, the supply voltage should be well-regulated to ensure the regular function. A self-cancellation DC-DC Buck converter (SC-Buck) is proposed to overcome the mismatch caused by process, voltage and temperature (PVT) variation and provide high accuracy supplying voltage. The proposed technique also overcomes the discontinuity in conventional offset cancellation scheme and doesn't need large silicon area which is required to decrease mismatch in conventional operational amplifier (OPAMP). Monte Carlo analysis demonstrates the reduction of mismatch. Without any trimming process, the proposed technique provides an output voltage drift within the tolerance of standard IEC60601-1 [7]. The test chip fabricated in UMC 28nm CMOS technology proves the output voltage accuracy can be improved to 97% since the mismatch of error amplifier (EA) can be suppressed from 122% to 1%.