Sensor/RF Digitization for IoT-Applications Using All-Digital-Very-Scalable-ADC TAD (invited paper)

T. Watanabe, H. Ishihara, T. Ito (DENSO CORPORATION, Japan)

As sensor and RF digitization for IoT-applications, this paper presents a concept of the digitization based on the all-digital-ADC TAD (Time A/D converter) as a both scalable and durable analog-interface using all-digital time-domain processing. TAD consists of all-digital circuits such as a Vin-supply-controlled ring-shaped pulse-delay-line (RDL) with 32 (in 0.65µm-CMOS), 64 (0.18µm-CMOS) or 128 (40nm-CMOS) inverters along with pure logic circuits (latch, encoder, counter and subtractor). Thanks to the all-digital construction, mixed-signal IC-design tradeoffs can be avoided and solved along even with advanced technologies. As sensor digitization examples, actual automotive sensors are explained including gyro-sensor implementation, which is one of the most difficult sensor digitization examples. Then, due to the all-digital architecture, scaling effects of TAD for RF-digitization are described including 40nm-CMOS simulation results (6mV/LSB at 1GS/s, 0.9mW and 0.014mm2). Finally, TAD methods, potentials and non-idealities are discussed with all-digital implementation even using FinFET technologies for future high-performance mixed-signal ASICs/SoCs.