Linear Regulator Part 12 - PCB Layout Guideline:

Linear Regulator Circuit Board Layout Guideline:

Stray capacitance and inductance may upset loop compensation and promote instability. Excessive input lead resistance increases the dropout voltage, and excessive output lead resistance reduces output load regulation. Ground loops also cause both problems. Careful layout is the solution.

Reduce stray capacitance and inductance by placing bypass and filter capacitors close to the regulator. Swamp parasitic reactance by using a 0.1µF ceramic capacitor (or equivalent) in parallel with the regulator input filter capacitor.

Excessive lead resistance, causing unwanted voltage drops and ruining load regulation, is solved by merely increasing conductor size. Regulators with remote sensing capability—adjustable—may utilize a Kelvin-sense connection directly to the load. Figure shows, an additional pair of wires feeds back the load voltage to the regulator sense input. This lets the regulator compensate for line drop. As the Kelvin sense leads carry only the small voltage-programming resistor current, they may be very narrow traces or small diameter wire. A judicious layout is especially important in remote-sensed designs, since these long, high impedance leads are susceptible to noise pickup.