LDPR datasheet(14/20 Pages) LINER

14 / 20 page

LT3470A

3470afa

APPLICATIONS INFORMATION

PCB Layout

For proper operation and minimum EMI, care must be

taken during printed circuit board layout. Note that large,

switched currents ﬂow in the power switch, the internal

catch diode and the input capacitor. The loop formed by

these components should be as small as possible. Further-

more, the system ground should be tied to the regulator

ground in only one place; this prevents the switched cur-

rent from injecting noise into the system ground. These

components, along with the inductor and output capacitor,

should be placed on the same side of the circuit board,

and their connections should be made on that layer. Place

a local, unbroken ground plane below these components,

and tie this ground plane to system ground at one location,

ideally at the ground terminal of the output capacitor C2.

Additionally, the SW and BOOST nodes should be kept as

small as possible. Unshielded inductors can induce noise

in the feedback path resulting in instability and increased

output ripple. To avoid this problem, use vias to route the

VOUT trace under the ground plane to the feedback divider

(as shown in Figure 5). Finally, keep the FB node as small

as possible so that the ground pin and ground traces will

shield it from the SW and BOOST nodes. Figure 5 shows

component placement with trace, ground plane and via

locations. Include vias near the GND pin, or pad, of the

LT3470A to help remove heat from the LT3470A to the

ground plane.

Figure 5. A Good PCB Layout Ensures Proper, Low EMI Operation

VOUT

3470a F05

SHDN

VIN

GND

LDPR Datasheet(PDF) 14 Page - Linear Technology