European IBIS Summit · PDF fileEuropean IBIS Summit ... Global Model Structure : ......
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Transcript of European IBIS Summit · PDF fileEuropean IBIS Summit ... Global Model Structure : ......
1. I/O Buffer Model Structure
2. Nonlinear Dynamic Behaviors Driver’s Last Stage
3. Output admittance I-Q Model
4. Model Extraction Procedure
5. Step Input Describing Functions
6. Example of Extraction Results
7. Conclusions
Presentation Outline
2 2
I/O BUFFER MODEL STRUCTURE
3 Objective: Develop a effective large-signal behavioral model Extraction
valid for transient simulation.
The two port input/output buffer general structure with its relevant electrical variables.
Global Model Structure :
iH(.) and iL(.) are local nonlinear dynamic functions describing the
driver’s last stage output impedance.
wH and wL are step input describing functions (StDFs) capturing the
behavior of the predriver device stage.
PAD
VDDUpper-Devices
v1(t)v2(t)
i2(t)
Lower-Devices
i1(t)
Predriver Stage
iH(t)
iL(t)
Driver Last Stage
Predriver Stage
Control Circuit
Input
port
Output
port
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LAST’S STAGE DRIVER BEHAVIOR
Nonlinear dynamic characteristic of the output port for the lower device under
pulse excitation.
The looping in the trajectory in the I-V plane is a clear indication
that the voltage-dependent capacitive effect is significant in the
behavior of the one-port upper and lower devices of the driver’s last
stage.
i L (A
)
v2 (V)
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Output impedance I-Q Model
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At a constant input voltage v1, the output buffer can be considered as a one-port
voltage-controlled device
One-port quasi-static representation of the upper or lower devices of the driver’s last stage.
The description of this element in continuous-time domain is :
Model Extraction Procedure The new extraction procedure relies on the linear least-squares method.
It is possible to extract the Cj (.) and Gj(.) by only one transient measurement.
Firstly, the excitation voltage v2 is a pulse with short tr/tf that covers all the
voltage amplitude range. Then, we record the transient response v2(t), i2j(t).
Secondly, pick the duplicate values of the voltage amplitudes at different time
instants t1 and t2 that verify v2(t1) and v2(t2 ) their corresponding currents ij(t1) and
ij(t2 ) .
Thirdly, since the state functions are single-valued, so that they depend only
on the instantaneous excitation voltage, Cj (t1)= Cj (t2) and Gj (t1)= Gj (t2) .
0
v2(t) -V
time (ns)
3.3
-1
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t1 t3 tm tn tn+1 tm+1 t4 t2
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Model Function’s Extraction
The Cj (.) and Gj(.) functions are obtained by a linear inversion
The value of the output voltage derivative at the time instant tk
We can write the I-Q model for the time instants t1 and t2
W. Dghais, H. M. Teixeira, T. R. Cunha, and J. C. Pedro “Novel Extraction of Table-Based I-Q Behavioral Model for High-Speed Digital Buffers/Drivers”, IEEE Trans. on Components, Packaging and Manufacturing Technology March 2013.
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The transient identification signal data
Vi(t)
VDD
Vss
io(t)
RLOAD
Vo(t)
VDC
UP DOWN
•VDC = GND Vo
t
+
Vo
t
VCC
Vo
t
VCC
+
Vo
t
VOL
VCC •VDC = VDD
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StDFs Extraction The wL(.) and wH(.) give the transient information about the
predriver’s nonlinear dynamics
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EXAMPLE OF EXTRACTION RESULT
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Conduction and displacement single valued nonlinearities for the
upper, and the lower devices of the driver’s last stage.
0 1 2 3 4-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
V--(V)
iH--(A)
0 1 2 3 40
0.5
1
1.5
2
2.5
V--(V)
CH--(pF)
0 1 2 3 4-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
V--(V)
IL--(A)
0 1 2 3 40
0.5
1
1.5
2
2.5
3
V--(V)
CL--(pF)
VALIDATION RESULTS
1.4pF 0.23 pF
24 mW
3 pF
2.1 nH
Random Bit
Sequence
Digital Output Buffer
v2(t)
Z0=40 Ohms, Td =0.3ns
vnear-end(t) vfar-end(t)
PACKAGE LOAD
0 5 10 15 20 25 30 35-2
-1
0
1
2
3
4
time (ns)
vfar-end
(V)
TL model
IQ model
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CONCLUSIONS A new extraction procedure of the I-Q behavioral model is based
on the linear least-squares optimization method, which avoids the
drawbacks of nonlinear optimization algorithms (such as
instability, local minima, training time, and dependence on
parameter initialization) used for the training of artificial neural
networks-based models.
Additionally, the fast extraction and easy implementation
help the automation of the I-Q behavioral model generation.
The extracted I-V and Q-V functions physically describe the the
electrical output impedance of the driver’s last stage.
The proposed formulation is more accurate as the IBIS
model, for the same level of computational complexity.
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Thank You for your Attention
Questions?
