1 2 nd AMICSA Workshop – 1 & 2 September 2008 Linearity Performances Measurement of a Low Power 14-bit A / D Converter, tested in Representative Conditions of CCD Space Applications J.Y Seyler, F. Malou, A. Penquer – CNES France L. Dugoujon, C. Prugne - STMicroelectronics

2 2 nd AMICSA Workshop – 1 & 2 September 2008 Presentation Plan :  Introduction  The TSA1401 ADC & RHF1401 ( Hi Rel version )  Generalities  Motivation Aspects  Hi Rel Version  Accuracy of the Linearity Measurements Method  Measurements Method  Bench Description  Measurement Accuracy  Measurement Results  Conclusions & Perspective

3 2 nd AMICSA Workshop – 1 & 2 September 2008 Introduction : Particular Constraints of the Video Signal for ADC : –Perturbations during the conversion ( Reset Peak for CCD ) –Very different amplitudes for 2 consecutive samples ( obscurity followed by highly illuminated pixels ) –Linearity Performance of the A/D Converters = Major issue for space missions –Environment Hardness, Low Power Consumption –…–… The “ COTS ” ( “ Components Off The Shelve ” ) ADC announce today : –High performances, –Low Power consumption.  Our purpose : –Consider directly A/D converters available “ Off the Shelve ” –Evaluate these devices in test conditions representatives of CCD applications. –An additional space qualification work is to be paid for environment hardness insurance.

4 2 nd AMICSA Workshop – 1 & 2 September 2008 TSA1401 ADC and the HIREL one (1/3) :  Generalities about the TSA1401 : 14-bit, up to 30Msps sampling frequency ADC developed by STMicroelectronics using deep submicron CMOS technology combining high performances with very low power consumption.  Pipeline structure with digital error correction  Excellent static linearity and dynamic performances.  Dissipates 85 20Msps ( down to 10 Msps ).  = 5 times less power consuming than usual space ADC.

5 2 nd AMICSA Workshop – 1 & 2 September 2008 TSA1401 ADC and the HIREL one (2/3) : Motivation Aspects and reason for characterizing the TSA1401 : –Lowest known power consumption ( similar Speed & Resolution ADCs ) –Linearity performances announcement = very good : I.N.L. p/p <= 4 LSB DNL p/p <= 1.2 LSB. –SEL immune up to LET de 55 MeV/mg.cm² ( CNES tests ) –Also available in Space Grade from STM : “ RHF1401” with Space Evaluation :  ESCC specifications ( with CNES funding ),  QML-V Certification for US Qualification in progress. Nota : Results presented are from commercial grade version.

6 2 nd AMICSA Workshop – 1 & 2 September 2008 RHF bit ADC (1/2) :  Wide sampling range : 1.5Msps to 30Msps  20Msps  Input range : 2Vpp differential  90dB Fs = 20Msps, Fin = 5MHz  2.5V / 3.3V compatible digital I/O  Internal / External V-ref  Rad-hard : 300 kRad(Si) TID  Failure immune ( SEFI ) and Latchup immune ( SEL ) up to 120 MeV-cm²/mg at 2.7V and 125°C  QML-V, smd bit ADC Hermetic SO-14

7 2 nd AMICSA Workshop – 1 & 2 September 2008 RHF bit ADC (2/2) : Hirel Version, RHF1401 :  Proposed in a Ceramic SO-48 package.  Complete Evaluation Test program is carried out to demonstrate the high reliability of this ADC for Space Applications :  Including mechanical and thermal tests, endurance tests and a Construction Analysis.  Radiation Tests under Heavy Ions ( susceptibility to Single Event Effects )  and under Co60 dose  Rad-Hard product up to 300 kRad ( Si ).  First Radiation Tests : no Single Event Latch-up under heavy ions and no parameter deviations up to 1 MRad ( Si ) Total Dose.  Hi-Rel version of the ADC will be fully qualified before end 2008 : –Electrical Characterization –Screening + Life-Test 3000 h –Construction Analysis made at CNES –TID Tests : OK up to 150krads –Intended to be introduced into EPPL

8 2 nd AMICSA Workshop – 1 & 2 September 2008 Accuracy of the linearity measurements method : Measurements Method Bench Description Measurement Accuracy

9 2 nd AMICSA Workshop – 1 & 2 September 2008 Linearity Measurement Method :  Histogram generated with “ Analogue Stimulus Generator ” : 16-bit resolution Analogue Voltage to the ADC. Ramp Function excitation ( sweeps full-scale range a given number of times with the same occurrence probability at each voltage step )  Because : “ Traditional Sine wave excitation” is too far from real CCD signal.  D.N.L. and I.N.L. can be extracted from the sampled histogram, if we note : (1) (2) (3)

10 2 nd AMICSA Workshop – 1 & 2 September 2008 Analogue Signal Generated : Figure 1 : “ Quasi-Static ” Test Mode Figure 2 : “ Perturbated ” Test Mode Figure 3 : “ Alternated ” Test Mode Generation of 3 types of signals :  “ Quasi-Static ” Test Mode ( Light Intensity linear variations ) : –The signal is a ramp function –Each step of the ramp is sampled.  “ Perturbated ” Test Mode : –The signal is a ramp function with periodic perturbation levels. –Perturbation levels are not sampled.  “ Alternated ” Test Mode ( Consecutive sampling of a Dark pixel and Illuminated pixel) : –Ramp function with periodic perturbation levels. –Perturbation levels are sampled.

11 2 nd AMICSA Workshop – 1 & 2 September 2008 Bench Description : The Test Bench, in CNES, is composed of 4 parts : Analog Stimulus Generator ( Analog Card with FPGA, 16-bit D/A Converter, Differential Amplifier, … ) “ A/D Under Test ” mounted on a dedicated card. Power Supplies, Clock Generator to drive the ASG and the A/D Card Dedicated Software ( Clock Generators, Data Acquisition from A/D ) A/D card Stimulus Generator

12 2 nd AMICSA Workshop – 1 & 2 September 2008 Measurement Accuracy : DNL Measurement Accuracy can be computed knowing : ADC DNL ( ASG is supposed to have ideal linearity ), Number of ramps, ADC bit-resolution, Total analog noise ( ASG + ADC noises )  2 forms of measurement error : Systematic error ( because ASG has only discrete values ) Random error ( = Standard Deviation ) Systematic Error versus Noise : Measured with 0.05 LSB simulated ADC DNL. Total analog noise is measured to be 2.5 LSB_rms  Systematic error totally canceled ! DNL Random Error : ADC with theoretical null NLD on all codes obtained by simulation for different ramp numbers

13 2 nd AMICSA Workshop – 1 & 2 September 2008 Measurement Results

14 2 nd AMICSA Workshop – 1 & 2 September 2008 Measurement Results (1/2) : 1°)  TSA1401 : excellent Linearity Performances ( Quasi-Static 10 Msps ) : Test Mode Sampling Frequency Peak-to-Peak DNL Peak-to-Peak INL Quasi-Static1.25 Msps0.3 LSB3.5 LSB Quasi-Static10 Msps0.5 LSB4.1 LSB Perturbated10 Msps0.7 LSB5.3 LSB Alternated10 Msps1.3 LSB11 LSB 2°)  TSA1401 Measurements : Very good results in other Test Modes Decline observed in the case of Alternated 10Msps … DNL INL

15 2 nd AMICSA Workshop – 1 & 2 September 2008 Measurement Results (2/2) : In “ Alternated 10Msps ” : INL = 11 LSB p/p -> 2 x higher  But still compatible with the most space missions required performances Linearity Performances 10Msps : Perturbated Alternated Mode.

16 2 nd AMICSA Workshop – 1 & 2 September 2008 Conclusions and Perspective : –…

17 2 nd AMICSA Workshop – 1 & 2 September 2008 Conclusions and Perspective : CNES Test Bench allows measurements of Linearity Performances of 14-bit resolution ADC with a very good accuracy. Measured in representative conditions of CCD applications. Preliminary Linearity measurements on TSA1401  High Level Performances.  More devices have to be tested to confirm these results : RHF1401 to be several Temp. & Vdd conditions since few differences with TSA1401 ( # Package ).  The TSA1401 is confirmed to provide a valuable candidate as a 14-Bit 20Msps A/D Converter for demanding CCD space applications : Very Low Power Consumption, Excellent Linearity performance in Space CCD Application Conditions.  RHF1401 Hi-Rel version expected to provide similar excellence with full ESCC ( CNES funding) and QML-V space qualification before end 2008.

18 2 nd AMICSA Workshop – 1 & 2 September 2008 Thanks for your Attention … … and The Restaurant