LT8640 datasheet(13/26 Pages) AD

13 / 26 page

LT8642-1

Rev. 0

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APPLICATIONS INFORMATION

Low EMI PCB Layout

The LT8642-1 is specifically designed to minimize EMI

emissions and also to maximize efficiency when switching

at high frequencies. For optimal performance the LT8642-1

requires the use of multiple VIN bypass capacitors.

Two small <1µF capacitors should be placed as close as

possible to the LT8642-1, one capacitor on each side of

the device (CIN1, CIN2). A third capacitor with a larger value,

4.7µF or higher, should be placed near COPT1 or COPT2.

See Figure 1 for a recommended PCB layout.

For more detail and PCB design files refer to the Demo

Board guide for the LT8642-1.

Note that large, switched currents flow in the LT8642-1

VIN and GND pins and the input capacitors. The loops

formed by the input capacitors should be as small as

possible by placing the capacitors adjacent to the VIN and

GND pins. Capacitors with small case size such as 0402

or 0603 are optimal due to lowest parasitic inductance.

The input capacitors, along with the inductor and out-

put capacitors, should be placed on the same side of the

circuit board, and their connections should be made on

Figure 1. Recommended PCB Layout for the LT8642-1

CSS

OTHER SIGNAL VIAS

VOUT VIA

VIN VIA

GROUND VIA

86421 F01

CIN3

COUT

CIN1

CBST

CVCC

CIN2

LT8640 Datasheet(PDF) 13 Page - Analog Devices