MAX16841 Datasheet, PDF(13/18 Page) Maxim Integrated Products – Controller IC for Dimmable Offline LED Lamps

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MAX16841

Controller IC for Dimmable Offline LED Lamps

Layout Recommendations

Careful PCB layout is critical to achieve low switching

losses, and clean, stable operation. The switching-

converter portion of the circuit has nodes with very fast

voltage changes that could lead to undesirable effects

on the sensitive parts of the circuit.

Follow the guidelines below to reduce noise as much

as possible:

1) Ensure that all heat-dissipating components have

adequate cooling.

2) Isolate the power components and high-current paths

from the sensitive analog circuitry.

3) Have a power ground plane for the switching-

converter power circuit under the power compo-

nents (input filter capacitor, output filter capacitor,

inductor, MOSFET, rectifier diode, and current-sense

resistor). Connect GND to the power ground plane as

close as possible to GND. Connect all other ground

connections to the power ground plane using vias

close to the terminals

4) There are two loops in the power circuit that carry

high-frequency switching currents. One loop is when

the MOSFET is on (from the input filter capacitor posi-

tive terminal, through the output capacitor, inductor,

switching MOSFET, and current-sense resistor, to the

input capacitor negative terminal). The other loop is

when the MOSFET is off (from the output capacitor

negative terminal, through the inductor, the rectifier

diode, and output filter capacitor positive terminal).

Analyze these two loops and make the loop areas as

small as possible. Wherever possible, have a return

path on the power ground plane for the switching

currents on the top-layer copper traces or through

power components. This reduces the loop area con-

siderably and provides a low-inductance path for

the switching currents. Reducing the loop area also

reduces radiation during switching.

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