Mixed-Signal ASIC for Rover Environmental Monitoring System

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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
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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

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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
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REMS ASIC GENERAL BLOCK DIAGRAM

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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

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REMS ASIC Block Diagram Interface
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REMS ASIC
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REMS ASIC ENVIRONMENT TECHNOLOGY

The REMS ASIC has been designed for a storing
temperature ranging from 135C to 125C and an
operating temperature ranging from 55C to
90C 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
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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
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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

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IR_COND Thermopile channels
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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
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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.

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REMS ASIC DIGITAL SECTION
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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
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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.
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REMS ASIC TEST RESULTS INFRARED CHANNELS

• Repeatability of parameters on different samples
• Gain accuracy 512,256,128,64,32 and 16 lt2.5.
• 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).

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REMS ASIC TEST RESULTS Pt 1000 channels

• Electrical test emulates sensor resistance
  variation with temperature by means of a 16 bit
  DAC-provided voltage

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REMS ASIC TEST RESULTS Pt 1000 channels
Gain and offset deviation over temperature
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BIAS SECTION CURRENTS STABILITY MATCHING
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SCREENING FLOW
The screening has been performed on 210 parts
according to requirements NASA GSFC EEE-INST-002
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SCREENING FLOW
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SCREENING FLOW

• Big effort has been put to find a glue for die
  attach able to survive at 135C
• 30 parts have been selected after screening and
  an extra electrical characterization has been
  performed (the measurements have been repeated
  between 55C and 90C with 10C step).
• On the 10 parts out of 30 have been performed
  further electrical test between 55C to 135C
  to verify the possibility to work at temperature
  near to mars atmosphere.
• Only one part doesnt work down to 65C
• 6 parts work correctly down to 135C but the
  parameters are out of specification
• 3 parts work correctly down to 135C with the
  expected parameters

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QUALIFICATION FLOW
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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).
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THERMAL CYCLING PLAN
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QUALIFICATION ACTIVITY THERMAL CYCLES
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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.