Electrical Rules Check (ERC) in PCB Design - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Electrical Rules Check (ERC) in PCB design?

ERC is a process that checks a PCB design for electrical errors like missing connections or wrong pin types before manufacturing.

beginner

Name two common errors that ERC detects.

ERC commonly detects unconnected pins and conflicting pin types (like output connected to output).

beginner

Why is running ERC important before PCB fabrication?

Running ERC helps catch electrical mistakes early, saving time and cost by avoiding faulty boards.

intermediate

How does ERC differ from Design Rules Check (DRC)?

ERC checks electrical connections and logic, while DRC checks physical layout rules like spacing and sizes.

intermediate

What should you do if ERC reports a pin conflict?

Review the schematic to fix the pin types or connections causing the conflict, then rerun ERC to confirm.

What does ERC primarily check in a PCB design?

A Solder mask layers

B Physical spacing between components

C Electrical connections and pin types

D Board outline dimensions

ERC focuses on electrical connections and pin compatibility, not physical layout.

Which error would ERC most likely detect?

A Copper trace width too narrow

B Two output pins connected together

C Component footprint misaligned

D Missing solder mask opening

ERC detects electrical conflicts like output-to-output pin connections.

When should you run ERC during PCB design?

A After soldering the board

B Only after PCB fabrication

C After placing components on the board

D After schematic completion and before layout

ERC is run on the schematic to catch electrical errors early.

If ERC reports an unconnected input pin, what does it mean?

A The input pin has no wire or signal connected

B The input pin is connected to ground

C The input pin is connected to an output pin

D The input pin is shorted to power

An unconnected input pin means it has no connection, which may cause circuit issues.

Which tool would you use to check physical spacing rules in PCB design?

A Design Rules Check (DRC)

B Electrical Rules Check (ERC)

C Bill of Materials (BOM) generator

D Gerber viewer

DRC checks physical layout rules like spacing and clearances.

Explain what Electrical Rules Check (ERC) is and why it is important in PCB design.

Think about how ERC helps avoid mistakes in the circuit wiring.

Describe the difference between Electrical Rules Check (ERC) and Design Rules Check (DRC).

One focuses on electrical connections, the other on board geometry.

Practice

1. What is the main purpose of Electrical Rules Check (ERC) in PCB design?

easy

A. To generate the bill of materials automatically

B. To check the physical dimensions of the PCB

C. To find electrical mistakes like unconnected pins early in the schematic

D. To simulate the circuit's electrical behavior

Solution

1. Step 1: Understand ERC's role in PCB design

   ERC is used to detect electrical issues such as unconnected pins or conflicting connections in the schematic.

2. Step 2: Differentiate ERC from other checks

   Physical dimension checks and simulations are separate processes, not part of ERC.

3. Final Answer:

   To find electrical mistakes like unconnected pins early in the schematic -> Option C

4. Quick Check:

   ERC = Find electrical mistakes early [OK]

Hint: ERC finds electrical errors in schematics before layout [OK]

Common Mistakes:

• Confusing ERC with physical layout checks
• Thinking ERC simulates circuit behavior
• Assuming ERC generates manufacturing files

2. Which of the following is the correct way to run an ERC in most PCB design software?

easy

A. Click the 'Run ERC' button after completing schematic edits

B. Export the schematic as PDF and review manually

C. Run a 3D visualization of the PCB

D. Generate Gerber files before running ERC

Solution

1. Step 1: Identify the ERC execution method

   Most PCB tools have a dedicated 'Run ERC' button or menu option to start the electrical rules check.

2. Step 2: Eliminate incorrect options

   Exporting PDFs, 3D visualization, and generating Gerber files are unrelated to running ERC.

3. Final Answer:

   Click the 'Run ERC' button after completing schematic edits -> Option A

4. Quick Check:

   Run ERC via dedicated button [OK]

Hint: Run ERC using the software's dedicated button [OK]

Common Mistakes:

• Thinking ERC runs automatically without user action
• Confusing ERC with file export or visualization
• Running layout checks instead of ERC

3. After running ERC, you see an error: Pin 'IN' on U1 is unconnected. What does this mean?

medium

A. The pin 'IN' is connected correctly and no action is needed

B. The pin 'IN' is connected to multiple nets causing a short

C. The component U1 is missing from the PCB layout

D. The pin named 'IN' on component U1 has no wire connected to it

Solution

1. Step 1: Interpret the ERC error message

   The message says the pin 'IN' on component U1 is unconnected, meaning no wire or net is attached to it.

2. Step 2: Understand implications

   An unconnected pin usually indicates a missing connection that may cause circuit malfunction.

3. Final Answer:

   The pin named 'IN' on component U1 has no wire connected to it -> Option D

4. Quick Check:

   Unconnected pin means no wire attached [OK]

Hint: Unconnected pin means no wire attached to that pin [OK]

Common Mistakes:

• Assuming unconnected means short circuit
• Confusing missing PCB part with schematic connection
• Ignoring ERC errors thinking they are warnings

4. You ran ERC and got multiple errors about conflicting pin connections. Which step should you take to fix this?

medium

A. Ignore the errors and proceed to PCB layout

B. Check the schematic for pins connected to multiple nets and correct wiring

C. Delete the entire schematic and start over

D. Run a 3D model check instead

Solution

1. Step 1: Analyze ERC conflict errors

   Conflicting pin connections mean pins are wired to more than one net, which is invalid.

2. Step 2: Correct schematic wiring

   Review and fix the wiring in the schematic to ensure each pin connects to only one net.

3. Final Answer:

   Check the schematic for pins connected to multiple nets and correct wiring -> Option B

4. Quick Check:

   Fix wiring conflicts in schematic before layout [OK]

Hint: Fix wiring conflicts in schematic, don't ignore ERC errors [OK]

Common Mistakes:

• Ignoring ERC errors and continuing
• Deleting schematic unnecessarily
• Confusing ERC errors with layout issues

5. You have a complex schematic with multiple power nets. ERC reports a warning that a power pin is connected to a net with a different voltage level. What is the best approach to resolve this?

hard

A. Verify the power net assignments and ensure pins connect only to nets with matching voltage levels

B. Ignore the warning if the circuit works in simulation

C. Connect all power pins to a single net regardless of voltage

D. Remove the power pins from the schematic

Solution

1. Step 1: Understand power net voltage warnings

   ERC warns when a power pin connects to a net with a different voltage, which can cause damage or malfunction.

2. Step 2: Verify and correct net assignments

   Check that each power pin connects only to the correct net matching its voltage level to avoid conflicts.

3. Step 3: Avoid unsafe shortcuts

   Ignoring warnings or connecting all power pins to one net can cause serious issues.

4. Final Answer:

   Verify the power net assignments and ensure pins connect only to nets with matching voltage levels -> Option A

5. Quick Check:

   Match power pins to correct voltage nets [OK]

Hint: Match power pins only to nets with correct voltage [OK]

Common Mistakes:

• Ignoring ERC voltage warnings
• Connecting different voltage nets together
• Removing essential power pins