PAM2842

Document number: DSxxxxx Rev. 1 - 2

13 of 17

www.diodes.com

October 2012

© Diodes Incorporated

PAM2842

A Product Line of

Diodes Incorporated

PCB Layout Guidelines

Careful PCB layout is important for normal operation. Use the following guidelines for good PCB layout: (BOOST)

1) Minimize the area of the high current switching loop of the rectifier diode and output capacitor to avoid excessive switching noise.

2) Connect high-cur rent input and output components with short and wide connections. The high-current input loop goes from the positive

terminal of the input capacitor to the inductor and the SW pin. The high-current output loop is from the positive terminal of the input capacitor

through the inductor, rectifier diode, and positive terminal of the output capacitors, reconnecting between the output capacitor and input

capacitor ground terminals. Avoid using vias in the highcurrent paths. If vias are unavoidable, use multiple vias in parallel to reduce resistance

and inductance.

3) Create a ground island (PGND) consisting of the input and output capacitor ground and PGND pin. Connect all these together with short, wide

traces or a small ground plane. Maximizing the width of the power ground traces improves efficiency and reduces output-voltage ripple and

noise spikes. Create an analog ground island (AGND) consisting of the output voltage detection-divider ground connection, the Sense-pin

connections between these separate ground planes.

4) Place the output voltage setting-divider resistors as close to the OV pin as possible. The divider's center trace should be kept short. Avoid

running the sensing traces near SW Pin.

5) Place the VIN pin bypass capacitor as close to the device as possible. The ground connection of the VIN bypass capacitor should be

connected directly to GND pins with a wide trace.

6) Minimize the size of the SW node while keeping it wide and short. Keep the SW node away from the feedback node. If possible, avoid running

the SW node from one side of the PCB to the other.

7) For the good thermal dissipation, PAM2842 has a heat dissipate pad in the bottom side, it should be soldered to PCB surface. As the copper

area cannot be large in the component side, we can use multiple vias connecting to other side of the PCB.

8) Refer to the example of a PAM2842 Evaluation board layout below.

TSSOP-20 Boost

QFN6x6-40 Boost

PCB Layout Example