Open-source design of integrated circuits: An open-sourced 1.44-MS/s 703-μW 12-bit non-binary SAR-ADC using 448-aF capacitors in 130-nm CMOS

This paper presents the design of a self-clocked 12-bit non-binary fully differential SAR-ADC using the SKY130 open-source PDK. The entire mixed-signal circuit design and layout were created with free and open-source software. The ADC reaches a sample rate of up to 1.44 MS/s at 1.8 V supply while consuming 703 μW of power on a small 0.175 mm ² area. A configurable decimation filter can increase the ADC resolution up to 16 bits while using an oversampling factor of 256. A 9‑bit thermometer-coded and 3‑bit binary-coded DAC matrix using a 448 aF waffle-capacitor results in a total capacitance of 1.83 pF per input. Realizations of configurable analog functions using the form factor of SKY130 high-density standard cells allow the parametrization of an analog circuit in a hardware description language and hardening of the macro in an intentionally digital workflow.