4 Design Considerations

Automotive camera modules are typically as small as possible to support placement in remote regions of the vehicle. A designer may need to sacrifice some layout best practices in terms of conducted and radiated emissions in order to meet stringent size constraints. The SSC feature of the TPS650350-Q1 allows for a sub-optimal layout while still passing CISPR-25 emissions testing specifications.

Design considerations for this layout to reduce emissions include:

1. Minimize the loop area between the buck converter input capacitors and the thermal pad of the PMIC. Smaller decoupling capacitors are placed closer to the device pins.
2. Minimize the loop area between the input capacitor, output inductor, and output capacitor of each buck converter.
3. The mid-voltage buck converter (Buck 1) has the highest priority for external component placement on the PCB.
4. The input capacitors for the low-voltage buck converters (Buck 2 and Buck 3) have the next highest placement priority.
5. External components for the less EMI critical converter can be placed on the opposite side. In this case the less critical converter is Buck 2 because it has a higher output voltage (1.8 V).
6. Incorporate multiple solid ground planes with low impedance connections to the ground pours on the external component layers.

Figure 4-1 Top Layer - Zoom