A 12.4fJ-FoM 4-Bit Flash ADC Based on the StrongARM Architecture

This work proposes an efficient 4-bit flash ADC based on the StrongARM comparator architecture. The proposed design eliminates the need for the resistive ladder by systematically modifying the sizing of the input differential pair of each comparator. As a consequence, the area and the power consumed within the ladder is eliminated. Furthermore, a Helpee StrongARM circuit is introduced which enables operation at an input voltage below the threshold voltage of the transistor. An enhanced 1-out-of-15 decoder converts the thermometer code from the StrongARM and the Helpee StrongARM comparators into a 1-out-of-n code. The proposed 4-bit flash ADC architecture, simulated in 90nm standard CMOS technology, consumes $292 {\mu } \mathrm {W}$ at 1.6 GHz sampling frequency, has an ENOB of 3.88 and FoM of 12.4 fJ/conv.step.

[1]  Jorge Pernillo,et al.  A 1.5-GS/s Flash ADC With 57.7-dB SFDR and 6.4-Bit ENOB in 90 nm Digital CMOS , 2011, IEEE Transactions on Circuits and Systems II: Express Briefs.

[2]  Abdullah Almansouri,et al.  Improved StrongARM latch comparator: Design, analysis and performance evaluation , 2017, 2017 13th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME).

[3]  Un-Ku Moon,et al.  Digitally synthesized stochastic flash ADC using only standard digital cells , 2011, 2011 Symposium on VLSI Circuits - Digest of Technical Papers.

[4]  Franco Maloberti,et al.  A 7.8-mW 5-b 5-GS/s Dual-Edges-Triggered Time-Based Flash ADC , 2017, IEEE Transactions on Circuits and Systems I: Regular Papers.

[5]  Jong-In Kim,et al.  A 65 nm CMOS 7b 2 GS/s 20.7 mW Flash ADC With Cascaded Latch Interpolation , 2015, IEEE Journal of Solid-State Circuits.

[6]  L. Richard Carley,et al.  ADC in 45nm LP Digital CMOS , 2009 .

[7]  Sayan Chatterjee,et al.  A 4-bit Asynchronous Binary Search ADC for Low Power, High Speed Applications , 2012, 2012 International Symposium on Electronic System Design (ISED).

[8]  Behzad Razavi,et al.  The StrongARM Latch [A Circuit for All Seasons] , 2015, IEEE Solid-State Circuits Magazine.

[9]  Anthony Chan Carusone,et al.  A 4-GS/s Single Channel Reconfigurable Folding Flash ADC for Wireline Applications in 16-nm FinFET , 2017, IEEE Transactions on Circuits and Systems II: Express Briefs.