fe8113 ”high speed data converters”. part 3: high-speed adcs

FE8113 ”High Speed Data Converters”

Part 3: High-Speed ADCs

G.Geelen et.al: “A 90nm CMOS 1.2V 10b Power and Speed Programmable Pipelined ADC With 0.5pJ/Conversion-Step”, IEEE ISSCC2006

S-T.Ryu et.al: “A 10b 50MS/s Pipelined ADC With Opamp Current Reuse”, IEEE ISSCC2006

T.Sepke et.al: “Comparator-Based Switched Capacitor Circuits For Scaled CMOS TEchnologies”, IEEE ISSCC2006

S.Gupta et.al: “A 1GS/s 11b Time-Interleaved ADC in 0.13µm CMOS”, IEEE ISSCC2006

Papers 10, 11, 12 and 13

G.Geelen et.al: “A 90nm CMOS 1.2V 10b Power and Speed Programmable Pipelined ADC With 0.5pJ/Conversion-Step

”

10b Pipelined ADC

This converter: 0.5pJ ,/(2 )ENOBs nyqFOM Power f

G.Geelen et.al: “A 90nm CMOS 1.2V 10b Power and Speed Programmable Pipelined ADC With 0.5pJ/Conversion-Step

”

Sampling to ground Sampling to virtual ground minimizes 1/f-noise and opamp offset

effects. However, high-frequency opamp noise is added during sampling

Large input transistor to minimze 1/f-noise

G.Geelen et.al: “A 90nm CMOS 1.2V 10b Power and Speed Programmable Pipelined ADC With 0.5pJ/Conversion-Step

”

Two-stage Miller opamp Folded cascode first stage

A0 ~ gm/go

A0 > 65dB over a large bias range

G.Geelen et.al: “A 90nm CMOS 1.2V 10b Power and Speed Programmable Pipelined ADC With 0.5pJ/Conversion-Step”

Measured dynamic performance

G.Geelen et.al: “A 90nm CMOS 1.2V 10b Power and Speed Programmable Pipelined ADC With 0.5pJ/Conversion-Step”

Performance summary

S-T.Ryu et.al: “A 10b 50MS/s Pipelined ADC With Opamp Current Reuse”

Pipelined ADC Two first stages: N-Input MDAC Two last stages: P-Input MDAC

P- and N-input MDACs share bias current

S-T.Ryu et.al: “A 10b 50MS/s Pipelined ADC With Opamp Current Reuse”

MDAC operation with simplified opamp schematic

S-T.Ryu et.al: “A 10b 50MS/s Pipelined ADC With Opamp Current Reuse”

Opampwith both P and N inputs Gain-boosted opamp with capacitive CMFB NMOS boost amplifiers. Capacitive level shifting allows NMOS

boost amplifiers for both P and N cascodes

S-T.Ryu et.al: “A 10b 50MS/s Pipelined ADC With Opamp Current Reuse”

0.18µm CMOS, 1.8V supply Power consumption: 18mW @ 50MS/s DNL: +/- 0.2 LSB, INL: +/- 0.4LSB ENOB: 9.2b/8.8b for 1MHz/20MHz inputs SFDR ~ 70dB

T.Sepke et.al: “Comparator-Based Switched Capacitor Circuits For Scaled CMOS

TEchnologies”

High-gain opamps without reduced signal swing is difficult to design in modern technologies

Open-loop amplification avoids this, but requires calibration New appraoch: Use a comparator to detect virtual ground

It is easier to detect the virtual ground than forcing it Will work for all sampled-data, switch-cap systems (filters, pipeline stages ++)

T.Sepke et.al: “Comparator-Based Switched Capacitor Circuits For Scaled CMOS Technologies

”

Comparator/loop delay results in overshoot Use a coarse and a fine current source With constant delay and current, this leads to a

constant offset at the output

T.Sepke et.al: “Comparator-Based Switched Capacitor Circuits For Scaled CMOS Technologies”

10b pipeline prototype design 1.5b stages, cascaded with no scaling

Proof-of-concept design

T.Sepke et.al: “Comparator-Based Switched Capacitor Circuits For Scaled CMOS Technologies”

Continuous-time comparator

T.Sepke et.al: “Comparator-Based Switched Capacitor Circuits For Scaled CMOS Technologies”

10b 8MHz pipeline 0.18µm CMOS, 1.8V supply Power consumption: 2.5mW @ 8MS/s DNL: 0.33/-0.28 LSB, INL: 1.59/-1.13 LSB Input-refferd rms noise: 0.65 LSB FOM: 0.3pJ/b

S.Gupta et.al: “A 1GS/s 11b Time-Interleaved ADC in 0.13µm CMOS”

11b 1GS/s TI-converter Input S/H switch to eliminate timing errors Double sampling in sub-ADCs to reduce the

number of sub-converters

S.Gupta et.al: “A 1GS/s 11b Time-Interleaved ADC in 0.13µm CMOS”

Double-sampled TI-architecture

S.Gupta et.al: “A 1GS/s 11b Time-Interleaved ADC in 0.13µm CMOS”

Timing scheme

S.Gupta et.al: “A 1GS/s 11b Time-Interleaved ADC in 0.13µm CMOS”

11b 1GSps TI-converter 0.13µm CMOS, 1.2V/2.5V supply Peak SNR: 58.6dB, peak SNDR: 55dB SNDR is 52dB with 400MHz input frequency FOM < 0.5pJ