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Linearity Performances Measurement of a Low Power 14-bit A / D Converter,tested in Representative Conditionsof CCD Space Applications J.Y Seyler, F. Malou, A. Penquer – CNES France L. Dugoujon, C. Prugne - STMicroelectronics
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 Presentation Plan :
Introduction : • Particular Constraintsof 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.
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 mW @ 20Msps ( down to 70mW @ 10 Msps ). = 5 times less power consuming than usual space ADC. TSA1401 ADC and the HIREL one (1/3) :
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 2269000 specifications ( with CNES funding ), QML-V Certification for US Qualification in progress. Nota : Results presented are from commercial grade version. TSA1401 ADC and the HIREL one (2/3) :
14-bit ADC RHF1401 14-bit ADC (1/2) : • Wide sampling range : 1.5Msps to 30Msps • 85mW @ 20Msps • Input range : 2Vpp differential • 90dB SFDR @ 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 5962-06260 Hermetic SO-14
Hirel Version, RHF1401: Proposed in a Ceramic SO-48 package. Complete Evaluation Test program is carried outto demonstrate the high reliability of this ADC for Space Applications : Including mechanical and thermal tests, endurance testsand 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 ionsand 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 RHF1401 14-bit ADC (2/2) :
Accuracy of the linearity measurements method : Measurements Method Bench Description Measurement Accuracy
(1) (2) (3) 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 :
Figure 1 :“ Quasi-Static ” Test Mode Figure 2 :“ Perturbated ” Test Mode Figure 3 :“ Alternated ” Test Mode Analogue Signal Generated : 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 ofa Dark pixel and Illuminated pixel) : • Ramp function with periodic perturbation levels. • Perturbation levels are sampled.
StimulusGenerator A/D card 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 )
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
Measurement Results (1/2) : 1°) TSA1401 : excellent Linearity Performances( Quasi-Static Mode @ 10 Msps ) : 2°) TSA1401 Measurements : • Very good results in other Test Modes • Decline observed in the case of Alternated Mode @ 10Msps … DNL INL
Measurement Results (2/2) : • Linearity Performances measured @ 10Msps : • Perturbated • Alternated Mode. • In “ Alternated Mode @ 10Msps ” : • INL = 11 LSB p/p -> 2 x higher • But still compatible with the most space missions required performances
Conclusions and Perspective : • CNES Test Bench allows measurements of Linearity Performancesof 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 tested @ several Temp. & Vdd conditionssince few differences with TSA1401 ( # Package ). • The TSA1401 is confirmed to provide a valuable candidate asa 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.
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