ADP5140WACCZ-R7 datasheet(59/128 Pages) AD

59 / 128 page

Data Sheet

ADP5140

Rev. 0 | Page 59 of 128

PCB LAYOUT RECOMMENDATIONS

In any switching power supply, there are some circuit paths

that carry high dI/dt, which create spikes and noise. Some

circuit paths are sensitive to noise, such as feedback traces,

which must be devoid of spikes and noise. The key to proper

PCB layout is to identify these critical paths and arrange the

components and the copper area accordingly.

When designing PCB layouts, keep high current loops small. In

addition, keep sensitive traces and components away from the

switching nodes and the associated components.

Figure 96 shows a recommended PCB layout for the ADP5140.

The following layout rules are recommended for the ADP5140:

•

Place the input capacitor, output capacitor, and inductor

as close as possible to the IC and use short traces.

•

Use separate analog ground planes (GND) and power

ground planes. Connect the ground reference of sensitive

analog circuitry, such as output voltage divider

components, reference capacitors, and output capacitors of

the LDO regulators to analog ground. In addition, connect

the ground reference of the power components, such as

input and output capacitors of the buck and boost

regulators, to power ground. Use the internal ground

planes to connect the analog ground plane and power

ground plane together.

•

Connect the exposed pads of the ADP5140 to the internal

ground plane.

•

Separate the input power trace of each switching regulator.

Using BUCK1 and BUCK2 as an example, although

PVIN1 and PVIN2 are adjacent pins and are usually

connected to the same input power, do not connect them

directly near the IC pins. Use a separated input trace to

connect each PVIN pin to its input capacitor.

•

Ensure that the high current loop traces are as short and as

wide as possible. Using a BUCKx regulator as an example,

ensure that the high current path from the input capacitor

through the inductor, the output capacitor, and the power

ground plane back to the input capacitor is as short as possible

by making sure that the input and output capacitors share

a common power ground plane.

•

Place the feedback resistor dividers as close as possible to

the FBx pins to prevent noise pickup. Minimize the length

of the feedback traces away from the high current traces

and the switching nodes to avoid noise pickup.

CIN3

CIN4

L12

RVSET1

RMODE

RTOP2

RBOT2

LFILTER

CFILTER

COUT7

COUT8

CFB4

RFB4

CIN78

CIN1

CIN2

CIN1011

COUT11

COUT10

ADP5140

Figure 96. Recommended PCB Layout

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