Data Sheet

LT8641A

analog.com

Rev 0

19 of 35

APPLICATIONS INFORMATION

Low EMI PCB Layout

The LT8641A is specifically designed to minimize EMI emissions and also to maximize efficiency when switching at

high frequencies. For optimal performance, the LT8641A requires the use of multiple VIN bypass capacitors.

Place two small 1μF capacitors as close as possible to the LT8641A: Tie one capacitor to VIN1/GND1; tie a second

capacitor to VIN2/ GND2. Place a third capacitor with a larger value, 2.2μF or higher, near VIN1 or VIN2.

See Figure 46 for a recommended PCB layout. For more detail and PCB design files, refer to the LT8641A demo board

guide.

Figure 46. Recommended PCB Layout for the LT8641A

Note that large, switched currents flow in the LT8641A VIN1, VIN2, GND1, and GND2 pins, and the input capacitors

(CIN1, CIN2). The loops formed by the input capacitors should be as small as possible by placing the capacitors

adjacent to the VIN1/2 and GND1/2 pins. Capacitors with small case size such as 0603 are optimal due to lowest

parasitic inductance.

Place the input capacitors, along with the inductor and output capacitors, on the same side of the circuit board, and

connect these on that layer. Place a local, unbroken ground plane under the application circuit on the layer closest

V

V

V

V

1

6

11

16

GROUND PLANE

ON LAYER 2

20

R1

R2

CVCC

CBST

CIN1

CIN2

CIN3

COUT

L

RT

CSS

C1

RPG

17

7

10

21

V

V OTHER SIGNAL VIAS

GROUND VIA

VIN VIA

VOUT VIA