10.1 Layout Guidelines

Certain points must be considered before starting a layout work using the TPS53219A.

• Inductors, V_IN capacitors, V_OUT capacitors and MOSFETs are the power components and should be placed on one side of the PCB (solder side). Other small signal components should be placed on another side (component side). At least one inner plane should be inserted, connected to power ground, in order to shield and isolate the small signal traces from noisy power lines.
• All sensitive analog traces and components such as VFB, PGOOD, TRIP, MODE and RF should be placed away from high-voltage switching nodes such as SW, DRVL, DRVH or VBST to avoid coupling. Use internal layers as ground planes and shield feedback trace from power traces and components.
• The DC–DC converter has several high-current loops. The area of these loops should be minimized in order to suppress generating switching noise.
  • The most important loop to minimize the area of is the path from the V_IN capacitors through the high and low-side MOSFETs, and back to the capacitors through ground. Connect the negative node of the V_IN capacitors and the source of the low-side MOSFET at ground as close as possible.
  • The second important loop is the path from the low-side MOSFET through inductor and V_OUT capacitors, and back to source of the low-side MOSFET through ground. Connect source of the low-side MOSFET and negative node of VOUT capacitors at ground as close as possible.
  • The third important loop is of gate driving system for the low-side MOSFET. To turn on the low-side MOSFET, high current flows from VDRV capacitor through gate driver and the low-side MOSFET, and back to negative node of the capacitor through ground. To turn off the low-side MOSFET, high current flows from gate of the low-side MOSFET through the gate driver and PGND of the device, and back to source of the low-side MOSFET through ground. Connect negative node of VDRV capacitor, source of the low-side MOSFET and PGND of the device at ground as close as possible.
• Because the TPS53219A controls output voltage referring to voltage across V_OUT capacitor, the high-side resistor of the voltage divider should be connected to the positive node of V_OUT capacitor at the regulatioin point. The low-side resistor should be connected to the GND (analog ground of the device). The trace　from these resistors to the VFB pin should be short and thin. Place on the component side and avoid vias between these resistors and the device.
• Connect the overcurrent setting resistors from the TRIP pin to GND and make the connections as close as possible to the device. The trace from TRIP pin to resistor and from resistor to GND should avoid coupling to a high-voltage switching node.
• Connect the frequency setting resistor from RF pin to GND, or to the PGOOD pin, and make the connections as close as possible to the device. The trace from the RF pin to the resistor and from the resistor to GND should avoid coupling to a high-voltage switching node.
• Connect all GND (analog ground of the device) trace together and connect to power ground or ground plane with a single via or trace or through a 0-Ω resistor at a quiet point
• Connections from gate drivers to the respective gate of the high-side or the low-side MOSFET should be as short as possible to reduce stray inductance. Use 0.65 mm (25 mils) or wider trace　ad ) of at least 0.5 mm (20 mils) diameter along this trace.
• The PCB trace defined as switch node, which connects to source of high-side MOSFET, drain of low-side MOSFET and high-voltage side of the inductor, should be as short and wide as possible.
• Connect the ripple injection V_OUT signal (V_OUT side of the C1 capacitor in Figure 22) from the terminal of ceramic output capacitor. The AC-coupling capacitor (C7 in Figure 22 ) can be placed near the device.