1. SIS20:A CMOS ASIC for SOLAR IRRADIANCE SENSORS in MARS SURFACE
D. Vázquez, S. Espejo, J. Ceballos, A. Ragel, C. Aledo, L. Carranza, J.M. Mora, M.A. Lagos

2. INTRODUCTION ASIC DESCRIPTION EXPERIMENTAL RESULTS CONCLUSIONS
OUTLINE
INTRODUCTION
ASIC DESCRIPTION
EXPERIMENTAL RESULTS
CONCLUSIONS

3. INTRODUCCIÓN
Meteorological instruments typically present in orbital devices, Rovers, probes, etc.
Surface instruments complements information provided by orbital devices.
In the context of Mars: Meteorological stations in the Surface are critical to understanding the climate and atmospheric dynamics.
This work presents SIS20: A Mixed-Signal Front-End ASIC for a Solar Irradiance Sensor to be included in the METEO Package of the ExoMars2020 Mission.
It has been conceived in collaboration with INTA (National Institute of Aerospacial Technologies, Spain)

4. INTRODUCTION ASIC DESCRIPTION EXPERIMENTAL RESULTS CONCLUSIONS
OUTLINE
INTRODUCTION
ASIC DESCRIPTION
EXPERIMENTAL RESULTS
CONCLUSIONS

5. ASIC SIS20: ASIC DESCRIPTION
BLOCK DIAGRAM
SPI Interface
Processing Blocks
SRAM Memories and Registers
Control circuitry
Miscelaneous, etc
CLK
&
POR
Misc. Analog
MUXs
&
Digital
BUS
TIA 1
TIA 2
TIA 10 .
Trans-Impedance Amplifiers
Instr. Amplifier
& 16-Bits ADC
Instr. Amp & ADC
10-Bits DAC (Subranging)
10-Bits subr. DAC .
PCS 1
PCS 2
PCS 4
Program. Current Sources
GATOs
(References & Test signals)
Global Analog Test Observ.
8-bits CS DAC
8-Bits Current Steering DAC
BANDGAP
Vs & Is References
Voltage & Current Refs

6. ASIC SIS20: ASIC DESCRIPTION
BLOCK DIAGRAM
SPI Interface
Processing Blocks
SRAM Memories and Registers
Control circuitry
Miscelaneous, etc
CLK
&
POR
Misc. Analog
MUXs
&
Digital
BUS
TIA 1
TIA 2
TIA 10 .
Instr. Amplifier
& 16-Bits ADC
10-Bits DAC (Subranging) .
PCS 1
PCS 2
PCS 4
GATOs
(References & Test signals)
BANDGAP
Vs & Is References
8-bits CS DAC

7. SIS20: ASIC DESCRIPTION TIAs CHANNELS 1M/2pF RC High 100k/20pF RC Low
RC Networks for Low/High configuration modes
TIAs CHANNELS
1M/2pF
RC High
100k/20pF
RC Low
CMOS Switches for Offset meas & compensation
Photo-Diode
CMOS Switches for gain mode selection
Pad
2-stage Folded Cascode OTA
Chip
10 channels total:
9 Channels meas
1 Channel calibration.
Shared Reference Bias (internal) but external accesing for shielding

8. SIS20: ASIC DESCRIPTION
16-bit (1-bit sign) ADC Channel and Input Multiplexer
Dual Slope
50MHz On-chip Clock
FSM
DIGITAL CONTROL
Differential Input
Data Out
gain
Level-shift
Start
EoC
PREAMP-1
PREAMP-2
INTEGR.
COMPARATOR
PREAMP-1:
Capacitive input impedance
Programmable gain 1/50
PREAMP-2:
Unity gain
Signal accomodation by level shifting
CMOS
MUX
ADC
TIAs
PT1000
VREFs
Internal Signals etc.
Preamps can also be used as General purpose VGA.

9. SIS20: ASIC DESCRIPTION PCS Channels for Temperature Measurement
Based on Resistance dependence of PT1000 with temperature
I to V conversion by a digitally controlled 4-bit resolution Current Source
4-bit resolution Programmable Current Source [0, 750mA]
Internal Vref (0.3V)
Ground (0V) 4 3 2 1
CHIP
To ADC
From Digital Control
Common Node
4 Channels (PT1000)

10. SIS20: ASIC DESCRIPTION 10-bits Sub-ranging DAC
Topology based on a conventional resistive ladder structure + multiplexer
Used to improve the resolution of the processed data
Generates a 10-bit resolution voltaje reference [0; 2,5V] to be connected to the negative rail of the ADC channel.
LSB -> 2,441mV

11. BANDGAP OPAMP Feedback Loop
SIS20: ASIC DESCRIPTION
10-bits Subranging DAC
8-bits Current Steering Output DAC
Topology based on a conventional resistive ladder structure + multiplexer
Off-chip led
CS DAC
DAC output
Used to improve the resolution of the processed data
Used for calibration and monitoring
Range [0; 25.5mA]
LSB -> 100uA
Voltage & Current References
Generates a 10-bit resolution voltaje reference [0; 2,5V] to be connected to the negative rail of the ADC channel.
LSB -> 2,441mV
VREF = 2.5V
BANDGAP OPAMP Feedback Loop
IREF= 100uA R
External
Low Temp Coeff Resistor
ASIC Temperature (PTAT + Res.) & Power Supply (VDD divider) Indicators
All Voltage & Current References are derived from VREF & IREF

12. SPI Communication Interface
Memories
&
Registers
Processing
&
Control
Miscellaneous (Test)
Clock generator

13. INTRODUCTION ASIC DESCRIPTION EXPERIMENTAL RESULTS CONCLUSIONS
OUTLINE
INTRODUCTION
ASIC DESCRIPTION
EXPERIMENTAL RESULTS
CONCLUSIONS

14. Experimental Results 4mm 3.3V CMOS 0.35u RHBD (IMSE-RHBDLib) 68 pins
(I/O pins -> 5.0V)
Operating conditions: -125ºC to 50ºC
5mm

15. Experimental Results TIA Channel in Low & High Gain Modes
After leakage current compensation
The Slope represents the measured resistance
Maximun opamps offset measured over 10 samples: 470mV -125ºC)

16. Experimental Results 16-bits ADC Chain
Values accumulated over 256 measurements
Good behavior in terms of linearity and noise, but gain and offset errors need to be compensated by Earth.

17. Experimental Results
Programmable Voltage Reference [0; 2.5V] through the 10-bit DAC [0;25.5mA]
10-bit Current Steering DAC
Global Voltage Reference from Bandgap behavior vs Temperature
Max. Variation = ±21ppm/ºC
Mean = 2.48V
Standard Dev.= 0.45%

18. INTRODUCTION ASIC DESCRIPTION EXPERIMENTAL RESULTS CONCLUSIONS
OUTLINE
INTRODUCTION
ASIC DESCRIPTION
EXPERIMENTAL RESULTS
CONCLUSIONS

19. Conclusions
A Mixed-Signal ASIC (SIS20) in a standard CMOS 0.35mm technology has been presented.
It is a Front-End for a Solar Irradiance Sensor on the surface of Mars. (METEO package in the ExoMars2020 mission).
RHBD techniques have been applied and use the Rad-Hard Library developed at the Institute of Microelectronics of Seville (IMSE).
The ASIC and main block’s functionality have been briefly described.
The functional operation and technical specifications have been verified in the lab for the specified range of temperature (-125ºC to 50ºC).
The qualification of the ASIC is still pending. However, it is expected to be satisfactory attending previous experiences on ASICs of the same characteristics and designed in the same technology using RHDB techniques and the same Rad-Hard library.