Locate the device as close as possible to the
power MOSFETs to minimize gate driver trace runs,
the components related to the analog and feedback
signals as well as current sensing are considered
in the following:
- Separate power and signal/analog traces, and use a ground plane to provide
noise shielding.
- Place all sensitive analog traces and components related to COMP, FB,
ISNS+, IMON, ISET, and RT away from high-voltage switching nodes such as SW,
HO, LO, or CBOOT to avoid mutual coupling. Use internal layer or layers as
ground plane or planes. Pay particular attention to shielding the feedback
(FB) and current sense (ISNS+ and VOUT) traces from power traces and
components.
- Locate the upper and lower feedback resistors close to the FB pin, keeping
the FB trace as short as possible. Route the trace from the upper feedback
resistor to the required output voltage sense point at the load.
- Route the ISNS+ and VOUT sense traces as differential pairs to minimize
noise pickup and use Kelvin connections to the applicable shunt
resistor.
- Minimize the loop area from the VCC and VIN pins
through the respective decoupling capacitors to
the PGND pin. Locate these capacitors as close as
possible to the device.