The document describes a family of multi-channel readout integrated circuits (ROICs) developed for X-ray and gamma-ray spectroscopy in space applications. The ROICs called VATAs integrate pre-amplifiers, pulse shaping circuits, discriminators, and 10-bit analog-to-digital converters for each of their 32-64 channels. They deliver digital pulse amplitudes and pixel addresses with low power consumption of 0.2-1.3 mW per channel. The VATAs are being used on several space missions including Astro-H, BepiColombo, and FOXSI to perform radiation detection and spectroscopy of high-energy photons. Test results show the ASICs achieve good energy resolution and low

1. AMICSA 20101
Multi-channel Detector
Readout Integrated Circuits
with ADCs for X-ray and
Gamma-ray Spectroscopy in
Space
Sindre Mikkelsen1
, Dirk Meier1
, Jahanzad Talebi1
, Suleyman Azman1
, Gunnar Mæhlum1
1
Integrated Detector Electronics AS
Monday, September 6th 2010, 15:00 – 15:30

2. AMICSA 20102
Abstract
We are developing detector readout integrated circuits (ROICs) for X-ray and Gamma-ray
spectroscopy. The ROICs are applications specific (ASICs) for satellite instrumentation in space. The
ICs described in this article belong to the VATA family with integrated analog-to-digital converters
(ADCs) for fully digital readout of x-ray and gamma-ray detectors. The VATAs are ideal for the
readout of cadmium zinc telluride (CZT), cadmium telluride (CdTe), silicon pads and strips, and large
area avalanche photodiodes (APDs) with scintillators. The VATAs contain 32 and 64 pre-amplifiers
each followed by pulse shaping circuits and level comparators for triggering and address encoding.
Each channel contains a Wilkinson ADC that generates a 10-bit digital word proportional to the
amplitude of the input pulse. Upon interaction of radiation in the sensor the VATA delivers digital
signals proportional to the energy of the photon as well as a digital address corresponding to the point of
interaction. The power dissipation is as low as 0.2 mW per channel during normal operation.
VATAs are currently under test for the soft gamma-ray detector (SGD) and the hard x-ray imager
(HXI) on board of the ASTRO-H satellite mission to launch in 2014 (formerly NeXT). Both detectors are
Compton cameras based on silicon pads and strips, CdTe pixels and pixels, and APDs with BGO
scintillators. ASTRO-H will help to study the evolution and structure of the universe. ASICs of the same
family are also under test for one instrument in the Mercury Plasma Particle Experiment (MPPE) on
board of the BepiColombo mission to Mercury and for the FOXSI rocket experiment. This article
describes the VATA architecture and presents results from tests in the lab.

3. AMICSA 20103
Introduction
A Family of recently developed Multi-Channel Radiation
Detector Readout ASICs.
• Radiation Energy Spectroscopy
• Radiation Imaging
The ASIC family is at the moment being utilized for the
following space missions:
• ASTRO-H (JAXA)
• BepiColombo MMO (JAXA)
• FOXSI (NASA/JAXA)
Criteria for the ASICs
• Very low power dissipation
• Low electronic noise
• Size and weight – high level of electronic readout integration

4. AMICSA 20104
Space Application (1)
ASTRO-H
GM-I supplies ROICs for 2 instruments: HXI, SGDGM-I supplies ROICs for 2 instruments: HXI, SGD
Picture:
JAXA

5. AMICSA 20105
Space Application (2)
BepiColombo MMO
GM-I supplies ROICs for the MPPE instrument.GM-I supplies ROICs for the MPPE instrument.
Picture: JAXA

6. AMICSA 20106
Astro-H, BepiColombo (Astro-H, BepiColombo (HXI, SGD, MPPE)HXI, SGD, MPPE)
• The Hard X-ray Imager (HXI)The Hard X-ray Imager (HXI)
– 4 layers of double-sided silicon strip detectors4 layers of double-sided silicon strip detectors
(DSSD) absorbs soft X-rays (<30keV), but(DSSD) absorbs soft X-rays (<30keV), but
transparent for hard X-rays (>30keV)transparent for hard X-rays (>30keV)
– 1 layer of double-sided CdTe detector detects hard1 layer of double-sided CdTe detector detects hard
X-rays (20keV...80keV)X-rays (20keV...80keV)
– BGO well is active shieldBGO well is active shield
• The Soft Gamma-ray Detector (SGD) is aThe Soft Gamma-ray Detector (SGD) is a
– non-focusing soft gamma-ray, 10—600 keVnon-focusing soft gamma-ray, 10—600 keV
– narrow-FOV Compton telescope, rejectsnarrow-FOV Compton telescope, rejects
background radiationbackground radiation
• GM-I delivers the Read Out Integrated Circuits for theGM-I delivers the Read Out Integrated Circuits for the
Silicon and CdTe detectorsSilicon and CdTe detectors
• BepiColombo MMO MPPEBepiColombo MMO MPPE
• Single sided strip detectorSingle sided strip detector
• Measure High Energy Particle energy to investigateMeasure High Energy Particle energy to investigate
thethe the structure and dynamics of the Mercury'sthe structure and dynamics of the Mercury's
magnetosphere.magnetosphere.
JAXA /
KIPAC
[Watanabe,
vertex 2009]

7. AMICSA 20107
Design criteria
• ASTRO-H SGD (VATA450), launch 2014:
– Very low power
– Medium DNR
• ASTRO-H HXI (VATA461), launch 2014
and FOXSI (VATA451), launch 2011:
– Low noise, medium power
– Low DNR
• BepiColombo MPPE (VATA460), launch Aug. 2013:
– Low power
– High DNR
– Medium noise
– Large temperature range

8. AMICSA 20108
Radiation Detector Principle

9. AMICSA 20109
VATA-ASIC Basic Functionality
Functionality Concept
Input: Readout of 32/64 radiation
sensors/electrodes/strips/pixels
32/64 parallel & independent inputs channels,
current input
Signal processing
• amplitude spectroscopy
• simultaneously and independent
32/64 x analog signal processing:
• charge sensitive amplifiers CSAs,
• Semi-Gaussian shapers,
• Discriminators
•10 bit ADC (integrating)
•Digital signal processing
Data sparsification •Analog amplitude discriminators to identify
events
•Digital data processing to minimize data output
Output: Delivers
•Asynchrounous trigger signal
•Digitized amplitude and pixel address
The trigger is set immediately after first
crossing of amplitude threshold. Digital data is
read out synchrounously by the system.

10. AMICSA 201010
ASIC TL architecture
Four distinct modes
of operation:
– Initialization
– Acquisition (FE)
– Conversion (ADC)
– Readout (BE)

11. AMICSA 201011
ASIC FE Channel Architecture

12. AMICSA 201012
The VATA PRINCIPLE

13. AMICSA 201013
ADC Architecture
• 32/64 channels converted in
parallel
• Integrating single slope ADC
(”Wilkinson”)
• 10 bit resolution
• 10MHz conversion clock
speed
• 1mW/channel power
consumption default, tunable
between 0.5-2mW
• 6 bit programmable offset
correction
• Common mode calculation
• Termination of conversion
phase when all channels have
been converted

14. AMICSA 201014
Back-End Architecture
• Digital data
reduction
• Output data
format:
– Status bits
– Trigger
map
– ADC data

15. AMICSA 201015
VATA-ASIC Extended Functionality
Function Implementation
User can adjust
•internal bias values
•adjust all thresholds individually
•enable or disable channels, adjust gain,
adjust power/noise, test individual channels
progammable configuration
register
Internal calibration pulse generation Individual channels can be tested
through a digital interface
Combine several ASICs ASICs can be Daisy-chained for
serial read-out, control and
configuration
Compensate change of external temperature Differential signals
Compensate large detector leakage current current compensation network
Electrostatic Discharge (ESD) protection Customized diodes at the inputs,
optimized for low noise

16. AMICSA 201016
ASIC Layout
JAXA / KIPAC [Watanabe, vertex 2009]

17. AMICSA 201017
Test results – Energy Spectroscopy (1)
VATA450 (low power)
JAXA / KIPAC [Watanabe et al., Vertex 2009] Data taken by JAXA / KIPAC
VA32TA6 VATA450

18. AMICSA 201018
Test results – Energy Spectroscopy (2)
VATA451 (low noise)
JAXA / KIPAC [Saito et al.,, SPIE 2010]
Noise
(ENC)
VATA450 59 +14 e/pF
VATA451 27 +6.6 e/pF
VATA460 179 +16 e/pF
VATA461 34 + 5.5 e/pF
ASIC measurements, by GM-I

19. AMICSA 201019
Test results (3)
VATA460 (HDR)
Threshold of Noise
Energy Resolution
(FWHM)
Energy measurement Thresh-hold
Energy[keV]
Temperature[degree]
Measurements performed by Takashima et al, JAXA.

20. AMICSA 201020
Test results (4)
VATA460 (HDR)
Energy Resolution (FWHM)
Under CC-on
Energy Resolution (FWHM)
under CC-off
Noise level under CC-off
Noise level under CC-on
Temperature[degree]
Energy[keV]
Measurements performed by Takashima et al, JAXA.

21. AMICSA 201021
Radiation Tolerance and Latch-up
Reference: H.Aihara, M. Hazumi, H. Ishino, J. Kaneko, Y. Li, D.
Marlow, S. Mikkelsen, D. Nguyen, E. Nygaard, H. Tajima, J. Talebi,
G. Vamer, H. Yamamoto, and M. Yokoyama, ”Development of
Front-end Electronics for Belle SVD Upgrades”, IEEE, Proc. Nucl.
Sci. Symp. Conf. Rec. 2000, Vol. 2, 9/213 – 9/216.
• The most sensitive structures
have been tested for radiation
tolerance
• ASIC fabricated in 0.35um
CMOS process with epitaxial
layer.
• ASIC fabrication process has
been choosen for good
radiation tolerance and latch-
up immunity.
• Initial SEL tests have been
performed, and the design has
passed these.

22. AMICSA 201022
Radiation test of VATA460
Radiation test by 6MeV/n He.
Measurements performed by Takashima et al, JAXA.
Gain Noise

23. AMICSA 201023
Legacy of GM-I ASICs in Space
Selection of most known missions:
• AGILE (launched April 2007). Two different ASICs for the ST instrument and
the SuperAGILE instrument: Luigi Pacciani, Ennio Morelli, Alda Rubini, Marcello Mastropietro, Geiland
Porrovecchio, Enrico Costa, Ettore Del Monte, Immacolata Donnarumma, Yuri Evangelista, Marco Feroci, Francesco Lazzarotto,
Massimo Rapisarda, Paolo Soffitta, “SuperAGILE Onboard Electronics and Ground Test Instruments”, Nucl. Instr. Meth. A 574, 2,
2007, 330-341.
• STEREO/PLASTIC (launched Oct. 2006, http://stereo.sr.unh.edu/): A.B. Galvin et al.,
“The Plasma and Suprathermal Ion Compositioin (PLASTIC) Investigation on the STEREO Observatories”, Space Science Reviews,
136, 1-4, April 2008.
• SWIFT/Burst Alert Telescope (launched Nov. 2004): L.M. Barbier, F. Birsa, J. Odom, S.D.
Barthelmy, N. Gehrels, J.F. Krizmanic, D. Palmer, A.M. Parsons C.M. Stahle, J. Tueller, “XA Readout Chip Characterization and
CdZnTe Spectral Measurements”, IEEE, Trans. Nucl. Sci. 46(1), 7, 1999.
• AMS (AMS-01 launch 1998, AMS-02 launch 2011): B. Alpat, ”Alpha Magnetic
Spectrometer (AMS02) Experiment on the International Space Station ISS”, Nucl. Sci. Tech. 14, 3, 2003.
• CREAM (balloon experiment, launch Dec. 2004): M.G. Bagliesi, C. Avanzini, G. Bigongiari,
A. Caldarone, R. Cecchi, M.Y. Kim, P. Maestro, P.S. Marrocchesi, F.Morsani, R. Zei, “Front-end electronics
with large dynamic range for space-borne cosmic ray experiments”, Nucl. Phys. Proc. Suppl. 172:156-158,
2007.
• GRIPS (balloon experiment, launch 2012).
• CALET, (launch 2013). To be installed on the ISS.
• ASIM (approved for ISS): S. Mikkelsen et al., ” A Low Power and Low Noise Multi-Channel ASIC for X-
Ray and Gamma-Ray Spectroscopy in Space”, Proceedings of AMICSA 2008.

24. AMICSA 201024
Single-event Upset (SEU)
• All configuration registers are implemented
with majority vote flip-flops, with 3 storage
cells.
• Automatic error correction
• Upsets are flagged externally using the trigger
line.
• Occurence of SEU events is flagged in the
output data stream.
Reference: Samo Korpar, Peter Krizan, Sasa Fratina, ”SEU Studies of
the Upgraded Belle Vertex Detector Front-End Electronics”, Nucl. Instr.
Meth., A 511 (2003) 195–199.

25. AMICSA 201025
Summary
• We developed a family of X-ray and Gamma
detector Read Out ASICs, suitable for a number
of space missions.
• Main achievements are.
– Reduced power dissipation
– Low noise
– High level of integration
• Other applications include:
– Nuclear medicine
– Security applications
– High energy physic

26. AMICSA 201026
Acknowledgments
We would like to thank our colleagues at JAXA
and Kavli/Stanford for good collaboration, and
for allowing us to use their test results in this
presentation.

27. AMICSA 201027
Appendix: Performance Specifications
Parameter Value Comment
Number of Input Channels
•VATA450/451
•VATA460/461
64
32
Readout for 32/64 pixels
Input charge dynamic range
•VATA450
•VATA451
•VATA460
•VATA461
±16
±1.6
±72
±5.5
Charge (fC), linear range. Some of the
ASICs have much higher saturation range
at higher non-linearity.
TP slow (VATA450/451//460/461)
TP fast
3/ 3/ 2/ 3.5
0.6/ 0.6/ 0.3 / 0.6
µs. Default settings.
Power consumption
•VATA450
•VATA451
•VATA460
•VATA461
0.25
1.16
0.336
1.28
Power consumption per channel (mW),
nominal bias settings. Acquisition mode.
Electronic noise of CSA
•VATA450
•VATA451
•VATA460
•VATA461
59 e + 14e / pF
27 e + 6.6e / pF
179 e + 16e /pF
34 e + 5.5e /pF
Baseline noise and noise slope. At default
bias values.
Detector Capacitance 5-7 Optimization value (pF).
Detector Leakage Current 10pA Optimization value. VATA460 has been
designed to tolerate up to 36nA.