A Design of 10-Bit Asynchronous SAR ADC with an On-Chip Bandgap Reference Voltage Generator.

Area of Science:

• Electrical Engineering
• Integrated Circuit Design
• Signal Processing

Background:

• Analog-to-Digital Converters (ADCs) are crucial components in mixed-signal systems.
• Optimizing power consumption and performance (speed, linearity) in ADCs remains a significant challenge.
• Successive Approximation Register (SAR) ADCs offer a balance of resolution and speed, but further improvements are sought.

Purpose of the Study:

• To propose and validate a novel 10-bit asynchronous SAR ADC prototype with an integrated bandgap reference voltage generator.
• To enhance power efficiency, static, and dynamic performance through innovative design techniques.
• To achieve high-speed conversion without relying on external high-frequency clocks.

Main Methods:

• Fabrication of a 10-bit 1 MS/s SAR ADC prototype using 130 nm technology.
• Implementation of a dual-path bootstrap switch for improved sampling linearity.
• Utilization of a Voltage Common Mode (VCM)-based Capacitive Digital-to-Analog Converter (CDAC) switching technique to reduce switching energy.
• Adoption of a two-stage dynamic latch comparator architecture for high speed and low power.
• Integration of asynchronous SAR logic with an internally generated clock for efficient time sequencing and single-cycle conversion.
• Inclusion of an error amplifier-based bandgap reference voltage generator for stable reference voltage.

Main Results:

• The fabricated SAR ADC achieved an Effective Number of Bits (ENOB) of 9.49 bits.
• A Signal-to-Noise and Distortion Ratio (SNDR) of 58.88 dB was measured.
• The ADC operated at a sampling rate of 1 MS/s with a 1.2 V power supply.
• The proposed design successfully integrated an on-chip bandgap reference voltage generator.

Conclusions:

• The developed asynchronous SAR ADC demonstrates competitive performance in terms of resolution and speed.
• The implemented techniques effectively address power consumption and linearity challenges in SAR ADCs.
• The integrated bandgap reference enhances the practicality and reduces the system complexity of the ADC.