10.1 Layout Guidelines
The PCB layout is an important step in the power supply design. An incorrect layout could cause converter instability, load regulation problems, noise, and EMI issues. Especially with a switching DC-DC converter at high load currents, too-thin PCB traces can cause significant voltage spikes. Good grounding is also important. If possible, TI recommends using a common ground plane to minimize ground shifts between analog ground (GND) and power ground (PGND). Additionally, the following PCB design layout guidelines are recommended for the TPS65150 device:
- Boost converter output capacitor, input capacitor and Power ground (PGND) should form a star ground or should be directly connected together on a common power ground plane.
- Place the input capacitor directly from the input pin (VIN) to ground.
- Use a bold PCB trace to connect SUP to the output Vs.
- Place a small bypass capacitor from the SUP pin to ground.
- Use short traces for the charge-pump drive pins (DRVN, DRVP) of VGH and VGL because these traces carry switching currents.
- Place the charge pump flying capacitors as close as possible to the DRVP and DRVN pin, avoiding a high voltage spikes at these pins.
- Place the Schottky diodes as close as possible to the device and to the flying capacitors connected to DRVP and DRVN.
- Carefully route the charge pump traces to avoid interference with other circuits because they carry high voltage switching currents .
- Place the output capacitor of the VCOM buffer as close as possible to the output pin (VCOM).
- The thermal pad must be soldered to the PCB for correct thermal performance.