# Category Archives: Hall of Fame

## ADC Survey: Spring 2011 update on FOM state-of-the-art

Experimental ADC data emerge like flowers in the spring.

Now I have finally completed the annual update of my ADC survey data. There’s a lot going on in the ADC field, so using scientific data only until March 2010 wasn’t going to be acceptable for much longer. Now the survey covers scientific ADC implementations reported all the way from 1974 until April/May 2011. Actually, I still have around 70 ADC papers from ESSCIRC 1975-1995 to read in order to make the survey backwards exhaustive, but those papers aren’t likely to change the content in this post. Therefore I’m not going to keep you waiting for this figure-of-merit status update any longer. Let’ get to the business:

# Influence on state-of-the-art

With the current update, the survey data now covers 1550 unique scientific papers and we could expect some changes to the state-of-the-art registered by the ADC FOM-o-meter.

### Standing Their ground

Not everything changes, though. Amazingly enough, the world record “Walden” or “ISSCC” FOM

$F_{A1} = \dfrac{P}{{2}^{ENOB}\times f_{s}}$

set to 4.4 fJ by van Elzakker et al. three years ago [1] remains unchallenged. Quite impressive, indeed!

### Pushing the envelope

The same SAR implementation by van Elzakker, also used to hold the state-of-the art “Thermal FOM”

$F_{B1} = \dfrac{P}{{2}^{2ENOB}\times f_{s}}$

for Nyquist converters, but a new record (7.6 aJ) was set by Hurrell et al. with a pipelined SAR ADC reported in December 2010 [2]. Observant blog readers may wonder why this design wasn’t already listed as state-of-the-art, since it was originally reported at ISSCC 2010. The answer is that the peak performance that nudged the state-of-the-art was measured at a very low $f_{in}$ (50 kHz), and that data point was not reported in the ISSCC paper – possibly in the slides. Since I wasn’t at the conference, any information shared in the slides was not available to me. Either way, congratulations to Christopher Peter Hurrell, and the rest of the team from Analog Devices UK and Ireland for this excellent design!

Finally, the overall best $F_{B1}$ reported by Pavan et al. [3], has been improved upon by a discrete-time DSM by Perez et al. [4] reporting a 2.7 aJ. Converter Passion is impressed by this significant contribution from Aldo Pena Perez and co-authors from University of Pavia, Italy. Congratulations!

# Hall of fame

All changes are now registered on the Converter Passion ADC FOM-o-meter page – your one stop solution for monitoring the evolution of A/D-converter figures-of-merit – and you can still find the previous (and current) state-of-the-art in the newly opened Converter Passion Hall of Fame. [See the new top menu “Hall of Fame” for different halls.]

So, what do you think: Was this result to be expected, or did you find anything surprising in the update? What do you think is the best approach in order to finally beat the van Elzakker record and send it to the Hall of Fame? 😉 [Michiel and co-authors, you are obviously welcome to share your thoughts as well. Is your 4.4fJ record unbreakable?]

#### References

[1]    M. van Elzakker, E. van Tuijl, P. Geraedts, D. Schinkel, E. Klumperink, and B. Nauta, “A 1.9μW 4.4fJ/Conversion-step 10b 1MS/s charge-redistribution ADC,” Proc. of IEEE Solid-State Circ. Conf. (ISSCC), San Francisco, California, pp. 244–245, Feb., 2008.

[2] C. P. Hurrell, C. Lyden, D. Laing, D. Hummerston, and M. Vickery, “An 18 b 12.5 MS/s ADC with 93 dB SNR”, IEEE J. Solid-State Circuits, Vol. 45, pp. 2647-2654, Dec., 2010.

[3]    S. Pavan, N. Krishnapura, R. Pandarinathan, and P. Sankar, “A 90μW 15-bit ΔΣ ADC for digital audio,” Proc. of Eur. Solid-State Circ. Conf. (ESSCIRC), Munich, Germany, pp. 198–201, Sept., 2007.

[4] A. P. Perez, E. Bonizzoni, and F. Maloberti, “A 84dB SNDR 100kHz Bandwidth Low-Power Single Op-Amp Third-Order ΔΣ Modulator Consuming 140μW”, Proc. of IEEE Solid-State Circ. Conf. (ISSCC), San Francisco, USA, pp. 478-480, Feb., 2011.