A Cyclic Vernier Two-Step TDC for High Input Range Time-of-Flight Sensor Using Startup Time Correction Technique.

Area of Science:

• Electrical Engineering
• Integrated Circuit Design
• Sensor Technology

Background:

• Traditional time-to-digital converters (TDCs) struggle with wide input ranges (>300 ns) due to area and power constraints.
• Limited linearity in cyclic TDCs for high input ranges is often caused by unaddressed startup time effects.
• Time-of-flight (TOF) sensors require high-performance TDCs for accurate distance measurements.

Purpose of the Study:

• To develop a low-power, wide-range, and linear cyclic Vernier TDC suitable for TOF applications.
• To address and compensate for the impact of startup time on TDC linearity.
• To achieve high resolution and accuracy in distance measurements using the developed TDC.

Main Methods:

• Proposed a cyclic Vernier two-step TDC architecture.
• Implemented digitally-controlled oscillators (DCOs) with dual frequency control and matched startup times.
• Utilized an alignment detector for startup time correction and a symmetric arbiter for precise edge alignment detection.
• Employed a current-reuse approach in the arbiter for low-power, high-speed operation.
• Fabricated the TDC using a 0.18 μm CMOS process.

Main Results:

• Achieved a wide dynamic range of 355 ns and a fine resolution of 377 ps.
• Demonstrated excellent linearity with Differential Nonlinearity (DNL) of 0.28 LSB_rms and Integral Nonlinearity (INL) of 0.96 LSB_rms.
• The TDC achieved a low power consumption of 0.65 mW in a compact area of 0.028 mm².
• When applied to TOF sensing, it enabled a distance range of 53.2 m with 5.65 cm resolution and an RMS error of 5.42 cm.

Conclusions:

• The proposed low-power cyclic Vernier TDC effectively overcomes the limitations of traditional designs for wide-range applications.
• The implemented startup time compensation technique significantly improves linearity, making it ideal for high-input-range TDCs.
• This TDC offers a promising solution for accurate and efficient distance sensing in TOF applications.