PCB Simulation

The increasing complexity of nowadays wireless RF devices increases the demand for accurate and efficient simulations of large and complex PCB designs. Identifying and predicting potential issues early in the design process saves resources, time, and money. SIwave helps you model, simulate and validate high-speed channels and complete power delivery systems typical in modern high-performance electronics. It accurately extracts multi-gigabit SERDES and memory buses, providing product sign-off compliance for various designs. SIwave’s full wave extraction of complete power distribution networks (PDN) enables you to verify noise margins and ensure impedance profiles are met through automatic decoupling analysis in low-voltage designs.

Overview

In this blog we will be setting up a serial channel on a PCB design using the HFSS 3D Layout tool in the ANSYS Electronics Desktop (AEDT). An eye diagram will be generated by linking the ANSYS HFSS Layout and ANSYS Circuit tools in the AEDT interface. The layout file will be simulated using the ANSYS SIwave solver, and ANSYS Nexxim transient solver will be used to perform the transient analysis.

Workflow

The work flow of this demo consists of the following steps:

a portion of the HDMI channel parasitics between the iMX6Q controller (U100) and connector (JL10) will be extracted. HDMI speed is 3.2 Gbps for 1080p with a 60 Hz refresh rate for 1920x1080 resolution. Nets of Interest are only:

• TX_TMDS1_P/N (Data)
• TX_TMDS2_P/N (Data 

Adjust SIwave Solution Setup

In this workshop we will be using SIwave solver to extract the SYZ parameters.

• In the Project Manager, expand Analysis
• Double click on Cosim Options (HFSS) to bring up the Co-Simulation Options dialog box
• Check the box for Setup override: and set it to SIwaveSYZ 1
• Check the box for Sweep override: and set it to Sweep1
• Click OK to close the Co-Simulation Options dialog box 

Setting Up the Circuit Design

After the SIwave analysis is performed, a circuit design can be inserted and the HFSS Layout design with the SIwave solution can be linked.

• Insert a circuit design to the project 
  • In the Ribbon, with the Desktop tab selected, click on Circuit to insert a Circuit design into the AEDT project. 
    
  • The Workflow dialog box appears. 
    
  • Select None and click on OK to close the Workflow dialog box. 
    
  • A new blank schematic appears. 
    

• Inserting the HFSS Layout model into the circuit design creates hierarchy. 
  
  • In the Project Manager window:
    
  • Right-click on the HFSS Layout design and select Copy
    
  • Right-click on the circuit design and select Paste.
    
  • Alternatively, the Layout design can be dragged to the circuit design.
    

You can edit the pin locations of the HFSS Layout component in circuit by right click on the component and select Edit symbol and then select Pin Locations..

You can then arrange the pins as seen below to make it easier connect the sources and terminations.

Adding Eye Sources and Eye Probes

To create an Eye diagram we need to add Eye Sources and connect them to the controller. Then we need to add Eye probes to measure voltage at the connector side.

The eye source Properties set to:

• trise= of 50 ps. 
• tfall = 50 ps. 
• UIorPBS to UnitInterval
• UIorBPSValue to UI with a value of 1/3.2 G.
• click on the BitPattern button, which opens the Bit pattern data dialog box
  
  • In the Bit pattern data dialog box set:
  • The radio button by Enter PRBS Data 
  • PRBS length to 15  
  • PRBS seed to 1
  • Click OK to close the Bit pattern data dialog box

After the 2 differential eye sources and 2 eye probes are added, we need to connect them to the controller and the connector as seen below. On the connector side, we need also to add a 100 ohm termination in parallel with the differential Eye probes.

Add Transient Solution Setup

To create the Eye diagram, a transient simulation needs to be performed inside the circuit design. The transient simulation will use the S parameters included in the Layout component that were calculated by the SIwave EM solve.

• In the Project Manager, right-click on Analysis under the Circuit design
• Select Add Nexxim Solution Setup… -> Transient Analysis
• This brings up the Transient Analysis dialog box
• In the Transient Analysis dialog box, set Start to 0.1 ns and Stop to 2us 
• Click OK to close the Transient Analysis dialog box

Create Eye Diagram Plot

After the transient simulation is done, we can create the eye diagram plot following the below procedures;

• In the ribbon, with the Results tab highlighted, click on the small triangle by Eye Diagram Report and select 2D to bring up the Report dialog box
• In the Report dialog box, under Trace tab, set: 
  
  • Solution to Transient Setup 1
  • Domain to Time
  • Unit Interval: enter 1/3.2e9 s
  • Eye Diagram: V(AEYEPROBE(1).out) , which is the voltage at the load resistor
• Click on the New Report button 
• Click on Close to close the Report dialog box

Below is the diagram plot.

we can also define a mask to be viewed with the eye diagram report. In order to add the data mask, open Edit eye mask dialog box:

• In the eye diagram plot, click on or near the X-axis (Time) at the bottom of the plot to select the X-axis  
• In the Properties window select the Mask tab
• Click the Edit button, which brings up the Edit eye mask dialog box

• In the Edit eye mask dialog box, click on the Edit button, which opens the Edit Dataset window
• In the Edit Dataset window, in the Coordinates area, enter the mask data:
• Time[ps]: 200ps and Voltage[mV]: 0mV
• Time[ps]: 250ps and Voltage[mV]: 200mV
• Time[ps]: 375ps and Voltage[mV]: 200mV
• Time[ps]: 425ps and Voltage[mV]: 0mV
• Time[ps]: 375ps and Voltage[mV]: -200mV
• Time[ps]: 250ps and Voltage[mV]: -200mV
• Time[ps]: 200ps and Voltage[mV]: 0mV
• Click OK to close the Edit Dataset window
• Click OK to close the Edit eye mask dialog box

And below is the eye diagram plot with the data mask shown.