With the provision to locate the controller 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 traces, and use a
ground plane to provide noise shielding.
- Place all sensitive analog traces and components related to COMP1, COMP2, FB1, FB2,
CS1, CS2, SS1, SS2, RES, and RT away from high-voltage switching nodes such as SW1, SW2,
HO1, HO2, LO1, LO2, HB1, or HB2 to avoid mutual coupling. Use internal layer or layers
as ground plane or planes. Pay particular attention to shielding the feedback (FB) trace
from power traces and components.
- Locate the upper and lower feedback resistors (if required) close to the
respective FB pins, keeping the FB traces as short as possible. Route the
trace from the upper feedback resistor or resistors to the required output
voltage sense point or points at the load or loads.
- Route the CS1, CS2, VOUT1, and VOUT2 traces as differential pairs to minimize noise
pickup and use Kelvin connections to the applicable shunt resistor (if shunt current
sensing is used) or to the sense capacitor (if inductor DCR current sensing is
used).
- Minimize the loop area from the VCC1, VCC2, and VIN pins through their respective
decoupling capacitors to the relevant PGND pins. Locate these capacitors as close as
possible to the LM25143-Q1.