Stefania Chicca – Aurelia Microelettronica Franco Bigongiari – Aurelia Microelettronica

1. Mixed-Signal ASIC for Rover Environmental Monitoring System Stefania Chicca – Aurelia Microelettronica Franco Bigongiari – Aurelia Microelettronica Jesus Lopez Soto – EADS Astrium Crisa Cascais, Portugal 2nd September 2008

2. PRESENTATION CONTENTS Rover Environmental Monitoring System • REMS ASIC Presentation • REMS ASIC Functional Overview • ASIC Analog interface • Internal Analog to Digital Converter • Test Activity: temperature tests and comments on test results • Qualification activity: actual status and qualification flow

3. REMS ASIC • MMars Mission in 2009 funded by NASA/Spanish Government • TTo investigate the past and present habitability at the surface of Mars • AAurelia is subcontractor of CRISA-EADS Astrium Front-end ASIC for wind, temperature and humidity sensors

4. REMS ASIC GENERAL BLOCK DIAGRAM

5. REMS ASIC building blocks • 12 PC sigma-delta channels to interface with wind sensors • 3 channels to measure the threshold temperature of sigma delta channels • 4 channels to amplify the thermopile signals • 1 channel to amplify the air temperature sensor signal • 1 channel to measure the temperature for thermopile calibration purposes • 1 channel to heat two of the thermopile sensors • 7 channels to amplify the temperature PT signals • 1 external channel • Power on reset generator • Voltage reference circuit • Bias section to provide current bias to the sensors and to the internal circuitry • 16 bit sigma delta A/D converter • Clock receiver on RS-422 Physical Layer and internal clock divider • Logic Control Unit, Configuration Registers, Output Data Registers • UART with RS-422 transmitter/receiver

6. REMS ASIC Block Diagram & Interface

7. REMS ASIC

8. REMS ASIC ENVIRONMENT & TECHNOLOGY The REMS ASIC has been designed for a storing temperature ranging from –135°C to +125°C and an operating temperature ranging from –55°C to 90°C The ASIC will be warmed up to the minimum operating temperature by an external heater prior to power up Latch up immunity is provided by XFAB 1.0um CMOS SOI-HV technology TID level requirement of 7Krad(Si) is not a concern for the selected technology: irradiation tests operated in the frame of other activities showed applicability up to 50Krad Single event upset mitigation is performed inside the digital section to avoid loss of functionality ASIC die size: 62.8 mm2 Assembled in CQFP100 package

9. REMS ASIC SENSOR INTERFACE RTemp interface: 7 Pt 1000 sensors are interfaced by the ASIC: internal controlled-current biasing is supplied to the sensor only during signal acquisition to limit self-heating: an internal multiplexer multiplexes the channels to the internal ADC and the biasing current to the sensor which is being acquired Air_Temp interface: 1 Pt 1000 sensor for measuring the Mars atmosphere temperature and 1 Pt 1000 sensor for measuring the infrared radiation source to calibrate the infrared temperature sensors Thermopile interface: 3 infrared sensors, whose conditioning chain inside the ASIC offers several programmable gains up to 2048 Therm_heater interface: an heater circuit able to provide up to 100mA is integrated into the ASIC to calibrate in flight the infrared sensors R_therm_cal interface: it is organized to bias and measure a PT 1000 resistor and it is used for calibration purposes WD_CON wind interface: 3 wind transducers treated inside the ASIC as sigma-delta channels

10. WD_COND SENSORS CHANNELS • 3 groups, 4 sensors each • each sensor is treated by a SD, that drives (with a current Inx) an external heater (Rheater) to keep Rx-sensor temperature at a given value (fixed by Rref, 1Rref/group) • bias currents for Rx and Rref are multiple of an unique current reference • internal adjusting on Rref bias current is provided in 64 steps • the drops on the 3 Rref resistors are amplified and converted by the ADC • all the heaters are activated in parallel • force and sense pins on Rref are separated

11. IR_COND Thermopile channels

12. Pt, Air_temp, IR_CAL, REF_Amp Channels Single-ended to differential conversion (with 2.5V common mode) common mode range: analog_ground 1 = 1V analog_ground 2 = 1.5V

13. REMS ASIC DIGITAL SECTION The digital section contains: • RS422 receiver • RS422 Transmitter • Control Unit The control unit decodes the command and prepares the answer, manages the acquisition from wind sensor channels and stores the data coming from ADC.

14. REMS ASIC DIGITAL SECTION

15. Y X z-1 1-z-1 z-1 1-z-1 1/4 1/3 1/4 Fig. ‑1: ADC z-domain representation REMS ASIC A/D CONVERSION Internal Analog to Digital II order sigma-delta converter is integrated with programmable conversion time: the converter provides an analog anti-aliasing active filter before conversion and a digital filter on converted samples after decimation down to 400Hz cutoff frequency: the noise filtering is achieved internally to the ASIC in this way (no need for software-processing the converted data). II order sigma delta ADC Decimation filter

16. REMS ASIC TEST ACTIVITY A dedicated test setup has been developed in Labview environment to allow automatic testing. On the right, the output for an infrared channel as a function of the input voltage is shown: however, relevant parameters are downloaded directly into datalog files.

17. REMS ASIC TEST RESULTS: INFRARED CHANNELS • Repeatability of parameters on different samples • Gain accuracy: 512,256,128,64,32 and 16 <2.5%. • 2048: max 3% • 8: max 2.8% • The output range of the channels is a valid value for the input ADC input range in all cases but one, (2048  3.5V, some saturation occurs at full scale).

18. REMS ASIC TEST RESULTS: Pt 1000 channels • Electrical test emulates sensor resistance variation with temperature by means of a 16 bit DAC-provided voltage

19. REMS ASIC TEST RESULTS: Pt 1000 channels Gain and offset deviation over temperature

20. BIAS SECTION: CURRENTS STABILITY & MATCHING

21. SCREENING FLOW The screening has been performed on 210 parts according to requirements NASA GSFC EEE-INST-002

22. SCREENING FLOW

23. SCREENING FLOW • Big effort has been put to find a glue for die attach able to survive at –135°C • 30 parts have been selected after screening and an extra electrical characterization has been performed (the measurements have been repeated between –55°C and 90°C with 10°C step). • On the 10 parts out of 30 have been performed further electrical test between –55°C to –135°C to verify the possibility to work at temperature near to mars atmosphere. • Only one part doesn’t work down to –65°C • 6 parts work correctly down to –135°C but the parameters are out of specification • 3 parts work correctly down to –135°C with the expected parameters

24. QUALIFICATION FLOW

25. QUALIFICATION FLOW REMS ASIC is classified as SCD Level 2 (Source-Vendor Control Drawing) according to EEE-INST-002 Section M3, Microcircuits, Monolithic: as a consequence, the qualification flow included in EEE-INST-002 is followed (to allow screening according to the reliability standard MIL-PRF-38535, Class Q, QML-38535).

26. THERMAL CYCLING PLAN

27. QUALIFICATION ACTIVITY: THERMAL CYCLES

28. CONCLUSION • A mixed-signal ASIC for signal acquisition and data conditioning has been presented • The ASIC will be used in a meteorological package, to be integrated in the Mars Science Laboratory Rover payload, for being launched on 2009. • The general architecture of ASIC has been presented and some blocks have deeply discussed • A summary of screening and qualification flow have been shown.