1 2 First Previous 21 Replies Latest reply on Aug 26, 2016 5:35 AM by robert_davies

    Electrical Design Rule Check drc-204: How to handle ceramic caps?

    martin.rottmann

      The drc-204 is used for "Voltage Drop Tolerance Check"

      How do you handle ceramic caps that have no polarity but a maximum operating voltage?

       

      The following picture shows a typical error that drc-204 should find. But C1 is connected with pin 2 to +12V and C2 is connected with pin 1 to +12V.

      As there are no drc_negative and drc_positive pins, how can I set up drc-204 correctly?

       

      I read every help page I could get. Also the video gives no clue for ceramic capacitors:

       

      Video: drc-204 Voltage Drop Tolerance Check (0h 07' 56")

        • 1. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
          robert_davies

          DRC 204 only covers polarized capacitors, it is not intended for this use case.

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          • 2. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
            martin.rottmann

            Thank you for the clarification.

            I thought for polarized capacitors is this check: drc-203: Component Polarity Check

            Help text: "This DRC checks to make sure the pins of a component are tied to the correct polarity."

             

            And drc-204 is Voltage Drop Tolerance Check

            Help text: "This DRC checks to make sure voltage across components meet manufacturer's tolerances."

            So I thought I can use this check for components as ICs, caps, resistors, etc which all can have a maximum operating voltage.

            Why it is limited to polarized caps?

            • 3. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
              robert_davies

              You could implement it but you would have to set the required values per instance or always place the capacitors in the same orientation each time and not perform pin swap.

              • 4. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                robert_davies

                Martin,

                It is not limited to polarized cap, the limitation is that you need to define the positive pin/supply pair, for polarized capacitors and IC pins this is fixed. In your case you're using a device with identical swappable pins - therefore you need to define the positive/negative pairs on a per instance basis or you need always connect the symbols using the same polarity.

                Rob

                • 5. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                  martin.rottmann

                  Yes, I understand that and thats what I thought, too. We can treat unpolarized components like polarized and every designer must take care to not use a ceramic capacitor or resistor the wrong way.

                   

                  I hope you can help me with two additional questions on this:

                  drc_voltage has an unusal definition with two values (minimum voltage and maximum voltage) in one property separated by semicolon (e.g. 50mV;6.3V)

                  How do you think this property can be defined and filled in the PDB? We already have a property "Voltage" that is for the maximum voltage (6.3V in the example). And there is a property "Vmin" for the minimum voltage.

                  Should we create a script that puts together the DRC voltage "50mV;6.3V"? Is it possible to just use the property "Voltage" wihout the minimum value and without the semicolon?

                   

                  Why is the minimum voltage in all your examples (help text, guidelines, video) always "50mV"? What happens if I enter "0V"? Will this work?

                   

                  Thank you for your help, Martin

                  • 6. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                    robert_davies

                    There is no relationship between the DRC settings and the PDB, nor for that matter anything found in Databook, so I would not suggest trying to tie these together in any way.

                    As for using 0V as the minimum, this is supported based on a simple test, we use the same 50mV across the documentation to be consistent.

                    • 7. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                      martin.rottmann

                      I do not understand completely, why the DRC has nothing to do with PDB or DxDatabook. Maybe I still have a wrong notion what the electrical DRCs should do.

                      My opinion: You have a polarized cap with a maximum operating voltage of 6.3V and it is erronously connected to +12V in the schematic. So the DRC should flag this as error.

                      But the DRC can only know about the 6.3V when the value is annotated at the symbol. And this information comes from the PDB or DxDatabook,

                       

                      Do you think the designer should provide instance data for every cap used in the schematic? What is the way a designer should work with the Verify tool? The help files mention a single maximum voltage for the whole board. But I cannot figure out for what this is for?

                      • 8. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                        robert_davies

                        The settings for DRC 204 (and Verify in general) are  totally independent of the part data as you can see from the configuration files you need to modify or that get modified via the UI. The only properties that appear on the symbol in this case are the DRC Positive and DRC Negative pin identifiers, all other values are entered into the Verify.ini or VerifyDefaults.ini files and applied globally.

                        You may wish for a more integrated and granular solution but this is how the tool functions at present and is part of our legacy with the product.

                        • 9. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                          martin.rottmann

                          Ok, I understand. Thank you for the explanation.

                          The VerifyDefaults.ini states in the <Defines> section:

                          <Option Name="drc_voltage" Value="DRC voltage" />

                          I thought that this maps to a property "DRC voltage" that can be annotated to a symbol.

                           

                          We have boards with many different voltages at once (+110V, +12V, +5V, +3.3V, etc) and therefore many different caps. I still cannot believe the only thing I can do is to define a board maximum voltage?

                          So how should the DRC-204 should work practically? What use case do you had in mind during requirements specification of drc-204?

                          • 10. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                            robert_davies

                            Martin,
                            Many of these checks are carried over from the legacy product from 2005 and earlier and were developed for specific user's use cases. We haven't yet seriously reviewed the functionality provided and have had little feedback in this area in a long while. If you consider that there should be a better solution within the product then you should review any currently logged enhancements on Ideas and vote for them, or submit new Ideas regarding the functionality you would like to see.

                            Rob

                            • 11. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                              martin.rottmann

                              Thank you, I really really appreciate your sincerity.

                               

                              Being a circuit designer for decades now, I cannot get rid of the feeling that there is no _real_ progress in the way doing computer added electrical circuit design. There are so many possibilities, so many ideas to move on. But instead we are all stumbling over the same things again and again.

                               

                              There are so many essentially good features but so many stop half the way. So here is my sincere list for xDx Designer:

                              - The net draw mode "avoidance" doesn't care for text, it only avoids parts.

                              - The multi net connection only works with pins and not with nets and busses

                              - There is an archiver that does not reveals how to restore an archive.

                              - There is a good iCDB Project Backup tool that cannot be opened from the DxDesigner tools menu (same thing with PCB Browser)

                              - There is a my parts (favorites) pane that does not work with DxDatabook parts (same with recently used)

                              - The bad performance of the hierarchical verification make it unusable

                              - The variant manager has some bizarre behavior when clicking on cells. It seems like a prototyped application.

                              - Opening the search/replace pane only focusses the cursor in the "find what" field the first time opening it. Never again.

                              - Pressing CTRL-H for replace does not open the replace pane but the find pane

                              - All hotkeys (like "n" for draw a net) only work for sheets that are already opened. For newly opened sheets you have to click somewhere in the background to make the hotkeys work.

                              - The pop functionality to go one step up the hierarchy does not work correctly. In reality it simply opens the last opened sheet. When you are jumping to a page with the search pane, you go back to the last opened sheet, which is not "going up the hierarchy".

                              - You cannot rotate clockwise and the position of your text properties, after rotating a part, are never as you want them.

                              - It is still a hassle with metric and imperial system although all distances should be computer internal unit-free values. The question about inch or mm should only interest the printer and not the librarian.

                               

                              For electrical circuit design, the computer is still used like a better sheet of paper with advanced copy/paste functionality.

                              I miss so many functions that have to do with numbers and data and electrical engineering. You at Mentor, you have it all, the netlist, the connection to the parts library, the customers parts database through DxDatabook, the layout. You have all this data.

                              How about:

                              • Calculating the voltage, current and power of a resistor dividers interactively
                              • Calculating of failure rates based on the real mission profile of the components (you know them, not the failure rate excel sheet)
                              • Show the designers what components they are currently using in the design. Let them easily minimize different components count.
                              • Tell the designer which components they used the most in the recent time. Warn them about e.g. two different 100nF caps (e.g. one with 6.3V one with 16V)
                              • Automatically suggest values for power supply feedback voltage dividers.
                              • Calculate currents and warn the designer interactively when a connected component is not suitable.
                              • Review your electrical design rules and _really_ implement checks for overvoltage, wrong polarity, missing voltages on power supply pins, missing pull ups
                              • <your idea here>

                               

                              Thank you very much,

                              Martin

                              • 12. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                                robert_davies

                                Martin,

                                I can't answer all of your points/questions here but at least we are addressing some of your needs in VX.2. If you post other Ideas then they will have a chance of being delivered too.

                                Of the issues you raise the following will be in VX.2:

                                 

                                My Parts will support DxDataBook properties

                                Pop will go back to the parent of the sheet you are currently in, not the one you last pushed from.

                                Clockwise rotation will be supported.

                                Text positions for rotated symbols will be embedded in the symbol view (Compound symbols)

                                 

                                Of the others, many are already in our backlog, but like all organizations we are limited by our resources.

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                                • 13. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                                  thomasle

                                  Very interesting discussion and explanations @Martin & @Robert

                                  Reading the descriptions of DRC 203 & 204 I would expect DRC 204 to be the right one for the ceramic capacitors, maybe I could be enhanced.

                                  Actually we don't use it as it causes too much efforts

                                  • 14. Re: Electrical Design Rule Check drc-204: How to handle ceramic caps?
                                    martin.rottmann

                                    Thank you for detailing the issues that will be addressed in VX.2. I really looking forward to this release. Is there already a (planned) release date?

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