The analog-to-digital converter (ADC) is one of the key components in many medical devices. It is also one of the main components which cost most power in these devices. The advantages of the successive approximation register (SAR) ADC are low power dissipation, medium speed and medium resolution and low energy per conversion-step. For these reasons, this architecture is suitable for medical devices.
Power consumption of ADCs can be reduced by decreasing the power supply voltage and the switch power of the capacitor arrays. However, for lower supply voltages, there is a tradeoff between the resolution and the speed.
The resolution of the ADC not only depends on the power supply, but also the offset voltage which is primarily caused by the mismatch of MOSFETs dues to the process variations. Calibrating these offset voltages is a very important issue for the high resolution ADC.