MIC2875 datasheet(17/24 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS20005549A-page 17

MIC2875

8.0

PCB LAYOUT GUIDELINES

PCB layout is critical to achieve reliable, stable and

efficient performance. A ground plane is required to

control EMI and minimize the inductance in power,

signal and return paths. The following guidelines

should be followed to ensure proper operation of the

device. Please refer to the MIC2875 evaluation board

document

for

the

recommended

components

placement and layouts.

8.1

Integrated Circuit (IC)

• Place the IC close to the point-of-load.

• Use fat traces to route the input and output power

lines.

• Analog grounds and power ground should be kept

separate and connected at a single location at the

PCB pad for exposed pad of the IC.

• Place as much as thermal vias on the PCB pad

for exposed pad and connected it to the ground

plane to ensure a good PCB thermal resistance

can be achieved.

8.2

IN Decoupling Capacitor

• The IN decoupling capacitor must be placed close

to the IN pin of the IC and preferably connected

directly to the pin and not through any via. The

capacitor must be located right at the IC.

• The IN decoupling capacitor should be connected

as close as possible to AGND.

• The IN terminal is noise sensitive and the

placement of capacitor is very critical.

8.3

VIN Power Path Bulk Capacitor

• The VIN power path bulk capacitor should be

placed and connected close to the VIN supply to

the power inductor and the PGND of the IC.

• Use either X5R or X7R temperature rating

ceramic capacitors. Do not use Y5V or Z5U type

ceramic capacitors.

8.4

Inductor

• Keep both the inductor connections to the switch

node (SW) and input power line short and wide

enough to handle the switching current. Keep the

areas of the switching current loops small to

minimize the EMI problem.

• Do not route any digital lines underneath or close

to the inductor.

• Keep the switch node (SW) away from the noise

sensitive pins.

• To minimize noise, place a ground plane

underneath the inductor.

8.5

Output Capacitor

• Use wide and short traces to connect the output

capacitor as close as possible to the OUT and

PGND pins without going through via holes to

minimize the switching current loop during the

main switch off cycle and the switching noise.

• Use either X5R or X7R temperature rating

ceramic capacitors. Do not use Y5V or Z5U type

ceramic capacitors.

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