magnetometer front-end asic (mfa) magnes 1), w., h. hauer 2), a. valavanoglou 1), m. oberst 2), h....

Magnetometer Front-end ASIC (MFA)

Magnes1), W., H. Hauer2), A. Valavanoglou1), M. Oberst2),H. Neubauer2), D. Pierce3), J. Means3), I. Jernej1), C. Hagen1),

W. Baumjohann1) and P. Falkner4)

1) Space Research Institute, Austrian Academy of Sciences2) Fraunhofer Institute for Integrated Circuits , Germany

3) Institute of Geophysics and Planetary Physics , UCLA, USA4) European Space Research and Technology Centre, ESA

AMICSA-08, 2nd Sept. 2008

IGPP/UCLA

2AMICSA-08, 02 Sept. 2008, Cascais/Sintra, Portugal

Magnetometer Front-end ASIC

Overview of System Level Design

Test Results and Performance

Summary of Radiation Tests

MFA-2 Summary Tables

Ongoing Redesign Activities

Application as 4- to 11-Channel Housekeeping ADC

Radiation Hardening Options for Missions to Jupiter

Conclusion










Conclusion


Block Diagram of MFA-2

Analog Part:

- 3 fluxgate channels with LNA

- 1 housekeeping channel w/mux.

- Reference generation

- 4 spare op-amps

Digital Part:

- Primary and sec. decimation filter

- 4-wire serial synchronous I/F

- Command decoder, Clk-generation

- Test bus interface


Fluxgate Sensor

Design of IGEP, TU Braunschweig (Germany)

- Rosetta, Venus Express, Themis

- a) Sensor core: 2 entwined ring-cores with pick-up coils

- b) Complete sensor: excitation, pick-up and feedback

Measures magnetic field vector: DC-100 Hz, pT to mT


Fluxgate Signals in Discrete Analog

CH1 /Id

CH2 /Is

CH1

CH2

CH01: signal after band-pass CH02: signal after pre-amplifier


Delta-Sigma Fluxgate

Fluxgate Sensor

First 2nd-Order Modulatorwith Modified Circuits

Second 2nd-Order Modulator(Standard Modulator)

Error Cancellation Logic

to Prim.Dec. Filter

1-bitDAC

x(t)

y(t)1 bit 21 bits

y(n) y'(n)

--

Modulator

FPGAINT1 INT2 COMP

LNA BPF

Sensor

BEX

-

fS : fD

SINCFILTER

16-24ADC

ASD

2f0

D-FF

fS=f0/232 :1

RFB

bits

dt dt Q D

Analog Fluxgate

INT

dt

Magnes W, et al. 2003A sigma-delta fluxgate magnetometer for space applications, Meas. Sci. Technol. 14 1003-1012


Package and Chip Monograph

Dig

ital

Par

t

Reference Generation

X-ChannelModulator

Y-ChannelModulator

Z-ChannelModulator

AdditionalModulator

Clo

ck G

en

erat

ion

& E

rro

r C

ance

lla

tio

n

Magnetometer Front-end ASIC (0.35μm CMOS from austriamicrosystems) in a 100-pin CQFP package being soldered to an adapter board

Chip micrograph of MFA-2 (ca. 20 mm2)










Conclusion


Final Test Configuration

MFA EGSE

- Interface adapter

- Power supply

- Connection to host-PC

VEXMAG sensor

- IGEP TU-Braunschweig

Test board (ver. 4)

- 9x6 cm2


Noise Performance (1/2)

10-1

100

101

102

103

10-3

10-2

10-1

100

101

102

103

PS

D [n

T/r

t(H

z)]

Frequency [Hz]

8 Hz, 100 nT peak

80 dB/dec

-100 -80 -60 -40 -20 00

20

40

60

80

100

SN

DR

(dB

)Input (dBFS)

SNDRmax=92dB @ -6dBFS

Ideally configured FLUX channel

- Noise floor <100 Hz dominated by sensor noise

- Increase of quant. noise of 80 dB/dec (gain setting correct)

- Harmonic distortion > 95 dB

SNDR and DR of HK channel

- Data after prim. decimation filter (128 Hz, fc=30 Hz)

- SNDRmax=92 dB

- DR=98 dB


Noise Performance (2/2)

MFA-1 (black) vs. MFA-2 (red)

- 1/f-noise in MFA-1 < 10 Hz

- No 1/f-noise in MFA-2 due to Correlated Double Sampling (CDS)

MFA-2 and MMS sensor (UCLA)

- Lowest noise level ever measured with this sensor

- 25 mm ring-cores with twin pick-up system

100

101

10-3

10-2

10-1

PS

D [

nT

/rt(

Hz)

]

Frequency [Hz]

MFA1-XMFA2-X

10-1

100

101

102

10-3

10-2

10-1

PS

D [n

T/r

t(H

z)]

[Hz]

DFG-P2-XDFG-P2-Y

10 pT/rt(Hz)

Noise Source: Sensor MFA ΣΔ


SNDR and Dynamic Range

Data rate [Hz]

Bandwidth [Hz]

SNR FLUX [dB]

DR FLUX [dB]

SNR HK [dB]

DR HK [dB]

128 30 85.0 91.0 92 98

64 24 86.2 92.2 93 99

32 16 88.5 94.5 96 102

16 8 90.1 96.1 99 105

8 4 93.0 99.0 102 108

4 2 95.8 101.8 105 111

2 1 97.2 103.2 108 114

Housekeeping Channel

- 128 Hz, fc=30 Hz: SNDRmax=92 dB, DR=98 dB


Fluxgate Channels



- Less performance gain at lower frequencies due to 1/f noise of fluxgate sensor










Conclusion


Radiation Tests (ESA Facilities)

TID test 1

- 2-2 cascaded modulator from Fraunhofer IIS

- Up to 115 krad

TID test 2 (MFA-1)

- Functional up to 260 krad

- Linear drop of SNDR(0.04 dB/krad)

TID test 3 (MFA-2)

- Functional up to 300 krad

- 1/f noise above 130 krad

Single Event Test (MFA-1)

- SEL LETTH of 14.1 MeV*cm²/mg

- σSAT of 10-3 cm2/device


TID Test with MFA-2

Fully functional up to 300 krad

Test board was configured in external voltage mode

- Fluxgate channels with different ranges and set-ups

Increase of 1/f-noise with TID above 170 krad

All four channels show same behaviour

No difference between internal and external voltage reference

Increased noise disappears after 10 day annealing at room temp.

10-2

10-1

100

101

102

103

104

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Frequency [Hz]

PS

D [F

S/r

t(H

z)]

X - 299krad/extRefY - 299krad/extRefZ - 299krad/extRefHK - 299krad/extRefHK - 4krad/extRef

10-2

10-1

100

101

102

103

104

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Frequency [Hz]

PS

D [V

/rt(

Hz)

]

HK - 299krad/extRefHK - 299krad/intRefHK - 0krad/extRefHK - 299krad/intRef/A_20°C_10days










Conclusion


Summary Tables

Process: CMOS 0.35 µm

Fabrication: austriamicrosystems

Layers: 2 poly, 4 metal

Chip area: 20 mm²

Package: CQFP-100

Gate equivalent (digital): 25,000

Transistors (analog): 14,000

Delta-sigma modulators: Three fluxgate, one housekeeping

Digital interface: 4-wire serial synchronous

Synchronization: Per command

Supply voltage: 3.3 V digital 3.5 V analog

Power consumption: 10 mW digital 50 mW analog 60 mW total

PCB area: < 9x6 cm2

Data interface: TLMH channel: 128 Hz

TLML channel: 2-128Hz

Total dose hardness: Full specs: 170 krad Functional : > 300 krad

Single event latch-up: > 14MeV•cm²mg-1

Dynamic range (field): < ±60,000 nT; 92 dB

Dynamic range (voltage):

± 1.25 V (differential); 108 dB ± 0.625 V (single-ended)

Digital resolution: 23 Bits

SNDR (field): 85 dB

SNDR (voltage): 97 dB

Offset stability (field) < 10 pT/°C MFA temperature < 0.4 nT/250h

Gain stability (field) 50 ppm/°C (± 2,000 nT range)

MFA Summary

MFA Resource Requirements

MFA Performance Characteristics










Conclusion


Block Diagram of MFA-3

FluxgateSensor

Fluxgate-Sigma-Delta2-2 Cascaded (X-Axis)

Fluxgate-Sigma-Delta2-2 Cascaded (Y-Axis)

Fluxgate-Sigma-Delta2-2 Cascaded (Z-Axis)

Sigma-DeltaH/K Channel

Sam

plin

g, E

rror

Can

cella

tion,

M

odul

ator

Con

trol

and

Fee

dbac

k

4 x

Prim

ary

Filt

erS

INC

^4 (

CIC

)O

SR

of 6

4 an

d 32

3 x Secondary Filterfor X,Y,Z

(6 x Boxcar Averaging)

Dat

a C

olle

ctor

,P

acka

ging

and

T

elem

etry

Uni

t

Command Decoder,Fluxgate and H/K Timing / Control

Analog ExcitationCircuit

3.3 VAnalogSupply

ReferenceVoltage

TestBus I/F

SerialInterface

3.3 VDigitalSupply

8:1 MUXCLK

(TLM

H)

TLM

L

CLK

CM

D

Spare OP 1, 2, 3 and 4

1 x Secondary Filterfor H/K

CMD

XY

ZH

/K

Hardware ControlTBEN / RST

MIXED ASIC - ANALOG

MIXED ASIC - DIGITAL

X,Y,Z,H/KLNA

LNA

LNA

ASD X, Y and Z OUTfor analog check-out

Reference Generation

Band-gap 1.2 V

1Hz S

ync

T_

Se

nso

r

Redesign is ongoing; Tape-out in Dec. 2008

Modifications in blue (minor) and red (major)

- Functional block basically the same as for MFA-2

NASA level 2 qualification in 2009 (Magnetospheric Multiscale Mission)

Proposed for Cross Scale Mission (Cosmic Vision M-class candidate)










Conclusion


MFA as General Purpose ADC

The MFA is at the same time a 4- to 11-channel general purpose ADC

Configuration A:

- 4 channels with 128 Hz data rate

- X, Y and Z with flexible input range up to ±10 V and HK (A1) with ±1.25 V

Configuration B:

- 3 channels with 128 Hz data rate and flexible range (X, Y and Z)

- 1 channel with 2 Hz and ±1.25 V; 5 channels with 2 Hz and ±0.625 V

- 2 additional channels measure supply voltage and MFA temp. with 2 Hz










Conclusion


Radiation Hardening

MFA-3 is a candidate for a number of missions in the frame of Cosmic Vision: e.g. Cross Scale (MFA-3 as is) and Laplace (radiation hard MFA required).

- Latch-up protection circuit is mandatory

It is considered to make future MFA designs fully radiation hard by

- either developing a rad-hard digital library for the currently used C35 process from austriamicrosystems

- or to transfer the current design to a process with an existing rad-hard, digital library (e.g. UMC 0.18 μm) in the upcoming years.










Conclusion


MFA Benefits

Miniaturization

TID hardness

Power consumption

Offset stability

with competitive performance!


Acknowledgements

The authors would like to thank the European Space Agency, Advanced Studies and Technology Preparation Division for funding this project under contract no. 18391/04/NL/HB

and the Institute of Meteorology and extraterrestrial Physics, Technical University in Braunschweig/Germany (namely Prof. K.-H. Glassmeier and K.-H. Fornacon) for the support of the MFA project with the fluxgate sensors of the Engineering Model magnetometer developed for the Venus Express mission.

magnetometer front-end asic (mfa) magnes 1), w., h. hauer 2), a. valavanoglou 1), m. oberst 2), h....

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