MIC45116 datasheet(27/42 Pages) MICROCHIP

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 2016 Microchip Technology Inc.

DS20005571A-page 27

MIC45116

6.0

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

MIC45116 module.

6.1

Module

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

• Use wide polygons to route the input and output

power lines.

• Follow the instructions in Package Information

and Recommended Landing Pattern to connect

the Ground exposed pads to system ground

planes.

6.2

Input Capacitor

• Place the input capacitors on the same side of the

board and as close to the module as possible.

• Place several vias to the ground plane close to

the input capacitor ground terminal.

• Use either X7R or X5R dielectric input capacitors.

Do not use Y5V or Z5U type capacitors.

• Do not replace the ceramic input capacitor with

any other type of capacitor. Any type of capacitor

can be placed in parallel with the ceramic input

capacitor.

• If a non-ceramic input capacitor is placed in

parallel with the input capacitor, it must be

recommended for switching regulator applications

and the operating voltage.

• In “Hot-Plug” applications, an electrolytic bypass

capacitor must be used to limit the over-voltage

spike seen on the input supply with power is

suddenly applied. If hot-plugging is the normal

operation of the system, using an appropriate

hot-swap IC is recommended.

6.3

RC Snubber (Optional)

• Depending on the operating conditions, a RC

snubber can be used. Place the RC and as close

to the SW pin as possible if needed. Placement of

the snubber on the same side as module is

preferred.

6.4

SW Node

• Do not route any digital lines underneath or close

to the SW node.

• Keep the switch node (SW) away from the

feedback (FB) pin.

6.5

Output Capacitor

• Use a wide trace to connect the output capacitor

ground terminal to the input capacitor ground

terminal.

• Phase margin will change as the output capacitor

value and ESR changes.

• The feedback trace should be separate from the

power trace and connected as close as possible

to the output capacitor. Sensing a long

high-current load trace can degrade the DC load

regulation.

Figure 6-1 is optimized from a small form factor point of

view shows top and bottom layer of a four layer PCB. It

is recommended to use mid layer 1 as a continuous

ground plane.

FIGURE 6-1:

Top and Bottom of a

Four-Layer Board.

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