ZXLD1371

ZXLD1371

Document number: DS35436 Rev. 1 - 2

40 of 42

www.diodes.com

February 2012

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Applications Information (cont.)

PCB Layout Considerations

PCB layout is a fundamental to device performance in all configurations.

Figure 20

shows a section of a proven

ZXLD1371 PCB layout.

Figure 20. Circuit Layout

Here are some considerations useful for the PCB layout using ZXLD1371 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-thro via holes. The ground plane should be unbroken as far as possible, particularly

in the area of the switching circuit including the ZXLD1371, 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 ZXLD1371, including the

centre 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 ZXLD1371 three evaluation boards have been developed which available via your

Diodes sales representative for qualified opportunities:

ZXLD1371EV1 Buck configuration

ZXLD1371EV2 Buck-boost configuration

ZXLD1371EV3 Boost configuration

SHP pin

decoupling

Inductor, Switch

and

Freewheeling

diode