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Ansoft proprietary
The Next State-of-the-Art in Circuit Simulation
Samuel Mertens, Mary TolikasAnsoft Corporation
Ansoft proprietary
Requirements for the next state-of-the-art circuit simulator
• Consistency across analysis domains• Model compatibility• High capacity• High speed• Accuracy• Robust convergence
NEXXIMNEXXIM
Ansoft proprietary
Nexxim supports all required analyses
• DC• Transient• Harmonic Balance
– Single tone / Multi-tone• AC
– AC / Time varying AC
Netlistor
Schematic
NEXXIMSimulation
Engine
Post-processing
• Noise– DC / Time-varying
• Sweeps– Variables– ALL model parameters
Ansoft proprietary
Nexxim providesresult consistency across domains
All analyses, whether time-domain or frequency-domain, use the same models and simulate
from the same netlist.* Gilbert cell mixer.SUBCKT GilCellMix 12 6 22 15 R6 9 28 20 R3 17 2 50 C3 0 2 1.0uF C1 12 10 1uF L1 10 21 0.5nH C4 15 7 1uF QBJT14 14 11 5 BJTM5 area=1QBJT10 6 24 17 BJTM3 area=1QBJT11 17 18 13 BJTM3 area=1QBJT2 9 11 20 BJTM3 area=1.model BJTM1 NPN Bf=1.30035647e2.ends GilCellMix
X1 3 4 Vif 7 GilCellMixV_SRC1 4 0 5.0 R2 7 5 50 RVif Vif 0 50 R3 3 2 50 V_LO 5 0 sin(0 0.1 1.75e9 0 0)V_RF1 2 break sin(0 0.0 2e9 0 0)V_RF2 break 0 sin(0 0.0 1.65e9 0 0).tran 0.01e-9 30e-9 0 3e-9.plot tran v(VIF)*HB:HB2 MaxOrder=4 Freq[1]=2000 MHz Order[1]=15.end
Time Domain
FrequencyDomain
Ansoft proprietary
Nexxim supports a variety of models•Passives
Resistors, Inductors, Capacitors•Independent/Dependent Sources•S-parameter elements (N-ports)•Transmission Lines (W elements)•Diodes
JUNCAPGeometricNon-GeometricFowler-Nordheim
•BJTsGummel-Poon & extensionsVBICPhilips MEXTRAM 503 / 504HiCUMHBT
•MOSFETsSchichman – HodgesBSIM3BSIM4Philips MOS 9 / MOS 11SOIEPFL – EKVHiSIM
•JFETs/MESFETsSPICECurticeStatzTriquint
•IBIS models
Ansoft proprietary
HFSS3D EM analysis
DESIGNERIntegrated Environment:
• Schematic Capture• Layout / Planar EM
• System analysis
Nexxim integrates with advanced EM and system tools
NEXXIMCircuit Simulation
Ansoft proprietary
Nexxim achieves highcapacity and speed
5 x12 x
BJT Mixer25 transistorsup to:1023 harmonics610,304 data pts.
MOS Mixerup to:1536 transistors856,256 data pts.
Ansoft proprietary
Nexxim offers highaccuracy at high speed
7 x
CompetitorNexxim
7 x7 x
CompetitorNexxim
NCSU sqrt example1188 BSIM3 transistorsTransient analysis
Ansoft proprietary
Nexxim offers high capacity and speed
Front-end for Bluetooth radio
2486 MOSFETs13 BJTs
24 minutes using Ansoft simulator3-tone Harmonic Balance
Ansoft proprietary
Nexxim offers robust convergence
Frequency Divider
Harmonic Balance Analysis
Large number of harmonics required to capture square-wave output
Nexxim converges in less than 1 minCompetitor does not converge
Ansoft proprietary
Nexxim integrates with system level design
0
0
0
0
0 0
gnd_psl_dff1_1vdd_psl_dff1_1
vdd_psl_dff1_1
gnd_psl_dff1_1
gnd_ANDcml_1vdd_ANDcml_1
vdd_ANDcml_1
gnd_ANDcml_1
vdd_psl_dff1_1
vdd_ANDcml_1
gnd_ANDcml_1
vdd_ANDcml_1
vdd_preamp_1
gnd_preamp_1
RbR
DbD
clkclkb
Qb
Q
bias
U1presclr_DFF
W_dff1=2u
AAbBBb
bias
QbQ
U2CML_AND
W_ANDcml=8u
inbin
biasout
outb
U17Pre_Amplifier
W_preamp_n=8uW_preamp_p=10u
W_preamp_src=30u
RbR
DbD
clkclkb
Qb
Q
bias
U18presclr_DFF
W_dff1=2u
AAbBBb
bias
QbQ
U19CML_AND
W_ANDcml=8uRbR
DbD
clkclkb
Qb
Q
bias
U20presclr_DFF
W_dff1=2u
RbR
DbD
clkclkb
Qb
Q
bias
U21presclr_DFF
W_dff1=2u
RbR
DbD
clkclkb
Qb
Q
bias
U22presclr_DFF
W_dff1=2u
RbR
DbD
clkclkb
Qb
Q
bias
U23presclr_DFF
W_dff1=2u
RbR
DbD
clkclkb
Qb
Q
bias
U24presclr_DFF
W_dff1=2u
AAbBBb
bias
QbQ
U25CML_AND
W_ANDcml=8u AAbBBb
bias
QbQ
U26CML_AND
W_ANDcml=8u AAbBBb
bias
QbQ
U27CML_AND
W_ANDcml=8u AAbBBb
bias
QbQ
U28CML_AND
W_ANDcml=8u
inbin
biasout
outb
U29Pre_Amplifier
W_preamp_n=8uW_preamp_p=10u
W_preamp_src=30u
M183
L=0.5uW=8uM=1
nch
M184
L=0.5uW=30uM=1
nch
10k
10k
V1277DC=1VO=1VA=0.5FREQ=f_clkTHETA=0
V1280DC=1VO=1VA=0.5FREQ=f_clkTHETA=180
+-
V1281DC=0 +
-
V1284DC=0 +
-
V1285DC=0
+-
V1288DC=2.5
+-
V1293DC=0 +
-
V1294DC=0 +
-
V1295DC=0
VV
V
V
V
V
V V V
V
ps_swalo2
ps_swalo1
to_asyn
bias
dff1_o1
clk
clkb
asyn_o3
div64_65
div64_65b
asyn_o2asyn_o1
bias_ANDcml
bias
bias
modsel_o
bias_ANDcml
real_2p5v
bias
bias_ANDcml
B=High, P=65B=Low, P=64
Starting Time + Bias Transient ~10.5nsStarting Time + Bias Transient ~10.5ns
PLL System Design For 1.8GHz GSM
Ansoft proprietary
Nexxim offers high capacity without loss of accuracy
SRAM cell
47,399 MOSFETs62,000 devices
Competitor does not provide the capacity “Approximate Spice” simulator does not provide the accuracy
422 seconds in Nexxim
Ansoft proprietary
Nexxim encapsulates technology advances in software engineering
State-of-the-art software engineering– C++ code from the ground up– Templated C++ code for all analyses– Automatic model compilation
User-defined models justas fast as library models
Ansoft proprietary
Nexxim encapsulates technology advances in numerics
Advanced Ansoft-proprietary numerics– New variable timestep integration formula for
Transient Analysis – New preconditioners for Harmonic Balance– New sparse matrix package that is faster than
industry standard
Ansoft proprietary
Nexxim offers faster preconditioned Krylov methods for HB
10x
These methods are industry standard for HB but are limited!
Ansoft proprietary
Nexxim advantages
• Higher capacity and speed for Harmonic Balance- Single tone- Particularly for multi-tone
• Robust convergence• Unique transient analysis features
- Improved error control- Novel integration techniques
• Consistency of results across domains- All analyses, whether time- or frequency-domain, use the same models
and simulate from the same netlist• Integration to EM tools
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