SATOM Test Time Reduction for Precision Analog ICs

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Enhance manufacturing efficiency with the SATOM test strategy, reducing test time by over 90% for precision analog and mixed-signal ICs. This innovative approach ensures better coverage and maintains high test accuracy, ultimately cutting down on manufacturing costs significantly.

  • Precision Analog
  • Test Strategy
  • ICs
  • Manufacturing Efficiency
  • SATOM
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  1. Test Time Reduction With SATOM Simultaneous AC-DC Test with Orthogonal Multi-excitation Degang Chen, Zhongjun Yu Iowa State University Krunal Maniar, Mojtaba Nowrozi Texas Instruments 2014 IEEE Ned Kornfield Best paper Award 1

  2. Purpose Final test time for precision analog and mixed-signal IC is long and is a major portion of total manufacturing cost The proposed SATOM test strategy will Reduce test time by well over 90% Provide better coverage Achieve the same test accuracy 2

  3. Outline Introduction The SATOM concept The SATOM test procedure Measurement results and comparison Conclusion 3

  4. Introduction Precision AMS IC s require high-precision measurements in final test Each measurement needs accurate and slow settling There are many AC/DC specs to be tested Leading to long test time on expensive test equipment large test cost 4

  5. Introduction An ADC is an multi input multi output device Input: Vip, Vin, Vrefp, Vrefn, AVDD, AVSS, DVDD, Output: Dout, busy, ready, Critical output: Dout AVDD DVDD Vicm+Vid/2 Dout ADC Vnoise Vicm-Vid/2 AVSS 5

  6. Introduction All input can cause response at Dout Since ADC is ratio-metric, ignore Vrefp, Vrefn Ideally, the interpreted output should be ????=???+ ?.?. But actually, we have ????=?(???,????,??????,????,????,????, 6

  7. Introduction State of the art ADC testing: Sequentially apply stimuli, measure Dout AVDD DVDD AC Vid Dout ADC Vicm DSP DC Vid AVSS Complicated setup and long test time 7

  8. The SATOM Concept Simultaneously apply multiple excitations AVdd+ 1 DVdd+ 3 Vicm+ 4+Vid/2 ADC Dout Vicm+ 4 Vid noise Vicm+ 4-Vid/2 AVss+ 2 CM and supplies at nominal values Vid large signal, all s small signals All signals are orthogonal sinusoids 8

  9. The SATOM Concept Orthogonal signals Nonzero signals , , , are mutually orthogonal over [0, T] if their inner products are zero: 1 , i j x x T x x x 1 2 3 T = = ( ) ( ) 0 x t x t dt i j i j 0 Sinusoidal signals of different frequencies are orthogonal over their common period 9

  10. The SATOM Concept Select Vid and i s to have different freq Make data record length common period Make sure harmonic distortions of Vid and intermodulation between Vid and i s all have different frequencies Vid, i s, all H.D. s, and all IMD s are mutually orthogonal over data record 10

  11. The SATOM Concept Collect a set of output over the common period under multi-excitation out id OS D V V V V c c d d + + + + + + + = + + + + . . V Q E noise ge id + + + + + 2 3 2 3 + id id + c c 1 1 2 2 3 3 + 4 4 ( ) d d V 1 1 2 2 3 3 4 4 V id + 2 ( ) e e e e 1 1 2 2 3 3 4 4 id 11

  12. The SATOM Concept Use inner products to computer coefficients , i out x D p = , x x 1 i i where xi is any of Vid, i s, H.D. s, or IMD s For example, if xi = Vid, we have , (1 ) id out ge V D = + = + , (1 ) V V rms id id ge id From this, gain error is computed Similarly, all other coefficients on last slide can be computed All inner products by FFT efficiently 12

  13. SATOM Test Procedure Select orthogonal multi-excitation frequencies Use a spreadsheet Select #samples in data record, M Select different integers J s as #periods for each excitation Check with spreadsheet that all excitations, all hd and all imd after aliasing are in distinct bins with sufficient separation all these are coherently sampled 13

  14. SATOM Test Procedure Compute signal frequencies by J = f f sig samp M Collect M samples Use FFT to compute all coefficients Convert results into specifications Computation steps are described in detail in the paper, illustrated with examples 14

  15. SATOM Test Procedure A word of caution With great effort in selecting coherent orthogonal frequencies, Actual generated signal may not be perfectly coherent In this case, use an FFT algorithm that handles non-coherent sampling Such as our ITC 11 or TIM 13 papers 15

  16. SATOM Test Procedure Identify and remove Vid fundamental Original spectrum vs after removing non-coherent fundamental 0 -20 -40 -60 -80 -100 -120 -140 -160 -180 0 200 400 600 800 1000 1200 1400 1600 1800 2000 16

  17. SATOM Test Procedure Identify and remove CM signal fundamental After removing non-coherent fundamental vs after removing non-coherent 0 -20 -40 -60 -80 -100 -120 -140 -160 -180 0 200 400 600 800 1000 1200 1400 1600 1800 2000 17

  18. SATOM Test Procedure Identify and remove IM2 s due to Vid* i 0 -20 -40 -60 -80 -100 -120 -140 -160 -180 0 200 400 600 800 1000 1200 1400 1600 1800 2000 18

  19. SATOM Test Procedure Remove of IM3, IM4, , the green spikes 0 -20 -40 -60 -80 -100 -120 -140 -160 -180 0 200 400 600 800 1000 1200 1400 1600 1800 2000 19

  20. Measurement Results Measurement results obtained at TI High resolution ADC used Main focus on INL, the most time consuming Repeatability established for fixed device Robustness across multiple good/ marginal / bad devices Accuracy measured against bench test Time reduction against production test 20

  21. Repeated INL measurements, a good device 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2.5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 Black: 4096 point SATOM; Red: 21 point bench21

  22. Repeated INL measurements, a bad device 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -10 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -20 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -30 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -40 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -50 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1.5 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2.5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 Black: 4096 point SATOM; Red: 21 point bench22

  23. Good Device 1, 10 INL curves Good Device 2, 10 INL curves Good Device 3, 10 INL curves Good Device 4, 10 INL curves Good Device 5, 10 INL curves 50 50 50 50 50 40 40 40 40 40 30 30 30 30 30 20 20 20 20 20 10 10 10 10 10 0 0 0 0 0 -10 -10 -10 -10 -10 -20 -20 -20 -20 -20 -30 -30 -30 -30 -30 -40 -40 -40 -40 -40 -50 -50 -50 -50 -50 -2.5 -2.5 -2.5 -2.5 -2.5 -2 -2 -2 -2 -2 -1.5 -1.5 -1.5 -1.5 -1.5 -1 -1 -1 -1 -1 -0.5 -0.5 -0.5 -0.5 -0.5 0 0 0 0 0 0.5 0.5 0.5 0.5 0.5 1 1 1 1 1 1.5 1.5 1.5 1.5 1.5 2 2 2 2 2 2.5 6 6 6 6 6 2.5 2.5 2.5 2.5 x 10 x 10 x 10 x 10 x 10 Blue: 1024 point SATOM; Red: 21 point bench 23

  24. Bad Device 1, 10 INL curves Bad Device 2, 10 INL curves Bad Device 3, 10 INL curves Bad Device 4, 10 INL curves Bad Device 5, 10 INL curves 50 50 50 50 50 40 40 40 40 40 30 30 30 30 30 20 20 20 20 20 10 10 10 10 10 0 0 0 0 0 -10 -10 -10 -10 -10 -20 -20 -20 -20 -20 -30 -30 -30 -30 -30 -40 -40 -40 -40 -40 -50 -50 -50 -50 -50 -2.5 -2.5 -2.5 -2.5 -2.5 -2 -2 -2 -2 -2 -1.5 -1.5 -1.5 -1.5 -1.5 -1 -1 -1 -1 -1 -0.5 -0.5 -0.5 -0.5 -0.5 0 0 0 0 0 0.5 0.5 0.5 0.5 0.5 1 1 1 1 1 1.5 1.5 1.5 1.5 1.5 2 2 2 2 2 2.5 6 6 6 6 6 2.5 2.5 2.5 2.5 x 10 x 10 x 10 x 10 x 10 Blue: 1024 point SATOM; Red: 21 point bench 24

  25. Comparison of test results: Specification ADC Offset Vindiff g.e. Vindiff gain AVdd PSR AVss PSR DVdd PSR Vicm reject Noise rms SNR(toFS) THD(toFS) SFDR(toFS) SNDR(toFS) ENOB(SNDR) Maximum INL Total time Quad test Excellent match with bench test in all parameters. New method 1.0741 mV -5.98% -0.54 dB -110.96 dB -88.19 dB -117.12 dB -107.17 dB 3.97 uV 112.51 dB -109.28 dB 113.35 dB 107.59 dB 17.61 bit 4.36 ppm (1024pts) 1 sec < 0.3 sec Standard method 1.076 mV -5.98% -0.54 dB -112 dB -88.5 dB -115 dB --- 4uV 112.5 dB -109 dB 113 dB 107.3 dB 17.6 bit 4.7 ppm (long) N.A. Final Test yes yes yes yes yes yes Yes (11 pts) > 14 sec 25

  26. Additional benefits of SATOM INL measured at many more points INL curve available Output power measured Intermodulation (IM2, IM3, ) between differential input and AVDD measured Intermodulation (IM2, IM3, ) between differential input and AVSS measured Intermodulation (IM2, IM3, ) between differential input and DVDD measured 26

  27. Conclusion Presented SATOM concept and algorithm It uses orthogonal multi-excitation with proper digital signal processing Demonstrated with high resolution ADC test Applicable to all multi-input analog and mixed-signal circuits and systems Reduced test time by well over 90% Improved test coverage, same test accuracy 27

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