ZXLD1371Q

ZXLD1371Q

Document number: DS37116 Rev. 1 - 2

39 of 42

www.diodes.com

September 2015

© Diodes Incorporated

ZXLD1371Q

PCB Layout Considerations

PCB layout is a fundamental to device performance in all configurations. Figure 20 shows a section of a proven ZXLD1371Q PCB layout.

Figure 20. Circuit Layout

Here are some considerations useful for the PCB layout using ZXLD1371Q in Buck, Boost and Buck-Boost configurations:



In order to avoid ringing due to stray inductances, the inductor L1, the anode of D1 and the drain of Q1 should be placed as close

together as possible.



The shaping capacitor C1 is fundamental for the stability of the control loop. To this end it should be placed no more than 5mm

from the SHP pin.



Input voltage pins, VIN and VAUX, need to be decoupled. It is recommended to use two ceramic capacitors of 2.2uF, X7R, 100V

(C3 and C4). In addition to these capacitors, it is suggested to add two ceramic capacitors of 1uF, X7R, 100V each (C2, C8), as

well as a further decoupling capacitor of 100nF close to the VIN/VAUX pins (C9). VIN and VAUX pins can be short-circuited

when the device is used in buck mode, or can be driven from a separate supply.



The underside of the PCB should be a solid copper ground plane, electrically bonded to top ground copper at regular intervals

using plated-through via holes. The ground plane should be unbroken as far as possible, particularly in the area of the switching

circuit including the ZXLD1371Q, L1, Q1 D, C3 and C4. Plated via holes are necessary to provide a short electrical path to

minimize stray inductance.

Critical positions of via holes include the decoupling capacitors, the source connection of the

MOSFET and the ground connections of the ZXLD1371Q, including the center paddle. These via holes also serve to conduct

heat away from the semiconductors and minimize the device junction temperatures.

Evaluation Boards

To support easier evaluation of the ZXLD1371Q three evaluation boards have been developed which available via your Diodes sales

representative for qualified opportunities:

ZXLD1371EV4

Buck Configuration

ZXLD1371EV5

Buck-Boost Configuration

ZXLD1371EV6

Boost Configuration

SHP pin

decoupling

Inductor, Switch

and

Freewheeling

diode