Common PCB Design Mistakes Leading to TPS65987DDHRSHR Failures and How to Resolve Them
The TPS65987DDHRSHR is a highly reliable USB Type-C and USB Power Delivery (PD) controller. However, like any complex IC, its proper functionality can be compromised by PCB design mistakes. Let's explore common issues and how to address them.
1. Incorrect Power Supply Design
Cause: One of the most common causes of failure in the TPS65987DDHRSHR is improper power supply design. The IC requires stable and correctly filtered power to function. If the power supply is not well-regulated, it could lead to unpredictable behavior or complete failure of the IC.
Solution:
Ensure that the V5V and VDD33 rails are correctly designed to provide a stable voltage. Use high-quality decoupling capacitor s close to the IC pins to filter out noise and voltage spikes. For instance, use 0.1µF ceramic capacitors along with larger electrolytic capacitors (e.g., 10µF or 100µF) to ensure stability. Implement proper ground planes and minimize the path impedance for power traces.2. Poor PCB Trace Routing
Cause: Incorrect or suboptimal trace routing can cause issues with signal integrity and power delivery. Long traces or traces with sharp bends can induce noise, voltage drops, or interference, especially for high-speed signals like USB and power lines.
Solution:
Keep traces short and direct. Try to minimize the length of high-frequency and power traces. Use wide traces for power and ground paths to minimize voltage drops and reduce the risk of thermal issues. Avoid sharp angles in traces—use 45-degree bends instead. This reduces the likelihood of signal reflections or interference. Use ground vias and solid ground planes to ensure a low-impedance path to ground.3. Improper USB Data Lane Design
Cause: The USB PD and data lanes (D+ and D-) are sensitive to signal integrity. Incorrect routing, inadequate impedance matching, or poor termination can result in communication errors or failure in establishing a connection.
Solution:
Route the USB differential pairs (D+ and D-) as tightly coupled and as short as possible. Ensure that the traces have a consistent 50Ω differential impedance. Place series termination resistors (typically 22Ω) close to the USB connector to avoid reflections and ensure signal integrity. Avoid crossing high-speed signals with power traces or noisy signals.4. Inadequate Grounding and Power Distribution
Cause: A poor grounding system is a major cause of PCB failures. If ground planes are fragmented or if there are ground loops, the performance of the TPS65987DDHRSHR can degrade due to noise, instability, or unexpected voltage shifts.
Solution:
Implement solid ground planes with minimal cuts to ensure a low-impedance return path for currents. Use multiple ground vias to connect different layers of the PCB to the ground plane. Ensure the ground traces are as wide as possible, especially where high current is flowing.5. Overlooking Thermal Management
Cause: Power Management ICs like the TPS65987DDHRSHR can generate significant heat, especially when switching high currents. Without proper thermal management, the IC can overheat, leading to thermal shutdowns or permanent damage.
Solution:
Add thermal vias to help dissipate heat from the IC. Use large copper areas or heat sinks to spread the heat away from the IC. Ensure adequate ventilation around the PCB and avoid placing the IC near heat-sensitive components.6. Failure to Meet USB-IF Design Guidelines
Cause: The USB Implementers Forum (USB-IF) has strict guidelines regarding USB PD and Type-C designs. Violating these standards can cause failures in communication, power delivery, and overall system stability.
Solution:
Follow the USB-IF reference designs and check your design against their specifications. Implement correct USB Type-C connector orientations, protection circuits (e.g., ESD protection diodes), and proper overcurrent protection. Make sure your design complies with the USB PD specifications, including voltage ranges and signaling levels.7. Incorrect or Inadequate Reset Circuit
Cause: The TPS65987DDHRSHR requires a proper reset sequence during power-up. Incorrect handling of reset pins or failure to meet timing requirements can prevent the IC from starting up correctly.
Solution:
Ensure that a proper reset circuit is included in your design, and check the timing requirements for the reset pin. Use a reset supervisor IC to ensure that the reset signal is generated correctly when the power is stable. Add debouncing capacitors to the reset pin to avoid spurious resets.8. Improper Component Selection and Sizing
Cause: Selecting components with inadequate voltage ratings or insufficient current handling capabilities can lead to failures in the system. For example, using a capacitor with an inappropriate voltage rating can cause it to fail and disrupt the power supply.
Solution:
Always choose components that are rated for the maximum voltage and current expected in the system. Verify that all components meet the specific tolerances and specifications listed in the TPS65987DDHRSHR datasheet.Summary of Solutions:
Power Supply: Ensure stable and filtered power with proper decoupling capacitors. Trace Routing: Keep traces short, wide, and avoid sharp bends. USB Data Lanes: Match impedance, route differential pairs tightly, and use series resistors. Grounding: Use solid ground planes with multiple vias to connect layers. Thermal Management: Use thermal vias and large copper areas to dissipate heat. USB-IF Compliance: Follow USB-IF guidelines for connectors and protection. Reset Circuit: Include a proper reset circuit with timing validation. Component Selection: Use appropriately rated components for voltage and current.By following these best practices and addressing common PCB design mistakes, you can ensure the reliability and functionality of the TPS65987DDHRSHR and prevent costly failures in your design.