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Optimizing Data Converters for High Frequency Operation

Optimizing Data Converters for High Frequency Operation. ADCs - Ping-Pong Architectures ADCs – Driving Them DACs – Sinc Compensation DACs – Glitches What They Didn’t Teach You in School. Ping Pong ADCs References. Analog Dialogue 37-8 (August 2003) Analog Dialogue 39-5 (May 2005)

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Optimizing Data Converters for High Frequency Operation

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  1. Optimizing Data Converters for High Frequency Operation ADCs - Ping-Pong Architectures ADCs – Driving Them DACs – Sinc Compensation DACs – Glitches What They Didn’t Teach You in School

  2. Ping Pong ADCsReferences • Analog Dialogue 37-8 (August 2003) • Analog Dialogue 39-5 (May 2005) • http://www.v-corp.com/ • Do a Patent Search on Inventor: Velazquez; Classification: 341/118

  3. Nyquist Theorem Limits Frequency Bandwidth

  4. Ping-Pong ADCSArchitecture

  5. Ping-Pong ADCSRaw Spectral Response

  6. Ping-Pong ADCSMatching Requirements

  7. Advanced Filter Bank (AFB)Reduces Spurs Due to ADC Mismatch

  8. Ping Pong ADCsTrimmed SFDR

  9. Ping Pong ADCsTemperature Effects

  10. Linear Error Compensation (LinComp)Corrects for Non-Linearities

  11. Driving ADCsReferences • Analog Dialogue 39-4 (April 2005) • Analog-Digital Conversion Seminar (2004)

  12. Transformer Coupling Gives Best High Frequency Performance

  13. ADC Drive

  14. Dual Transformers Improve Balance at High Frequencies

  15. Baluns Have a Wider Frequency Response

  16. Applying Voltage Gain Can Improve Noise Performance

  17. DACsSome Things You May Not Have Thought Of • Sinc Compensation Effects • Glitch Energy

  18. DACs Suffer From Sinc Response dB Frequency (xFs)

  19. Use Sinc Compensation to Reduce Passband Droop dB Frequency (xFs)

  20. Passband is Flat But There is 3.5 dB Insertion Loss dB Frequency (xFs)

  21. Sinc Compensation Doesn’t Work So Wellat Super Nyquist Bands dB Frequency (xFs)

  22. AD9779 Vs AD9777 Time Domain Plot Both DACs synthesizing a 1MHz sine wave in 1x interpolation mode with a 160MSPS clock rate. Due to the unique output stage of the AD9779, its time domain waveform has much more glitch energy than the AD9777 AD9777 AD9779

  23. Glitches Are Worsebut Noise Floor is Better

  24. Glitches Are Worsebut 3rd Order IMD Is better

  25. Things They Don’t Teach You In School • Watch ALL your inputs • Proper Decoupling • Differential Signaling • Clean Your Clock

  26. How many Inputs Does a Data Converter Really Have? A D D A A VD VA CSTRAY "QUIET“ DIGITAL Analog I/O NOISY DATA BUS ANALOG CIRCUITS DIGITAL CIRCUITS BUFFER LATCH B Clock A CSTRAY ID IA Reference AGND DGND A D V D A A ANALOG GROUND PLANE DIGITAL GROUND PLANE = = A D

  27. Power Supply Decoupling Must Be Effective at Very High Frequencies

  28. Why Differential Signaling?

  29. How Clean Does Your Clock Need To Be 1000 1000 SNR –1.76dB ENOB = 300 4 300 6.02 100 6 100 tj tj 8 30 30 (ps) (ps) 10 10 10 12 3 3 14 1 PLL WITH VCO 1 16 0.3 0.3 18 PLL WITH VCXO 0.1 0.1 DEDICATED LOW NOISE XTAL OSC 0.03 0.03 1 3 10 30 100 300 1000 FULL-SCALE ANALOG INPUT FREQUENCY (MHz)

  30. In Conclusion • Hopefully you learned something • Getting good high-frequency performance is tough • But there are some things you can do to get the best performance you can • Thank you for your kind attention • Please talk to you friendly local ADI Sales Engineer when you’re ready to start your next design

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