LTM4645 datasheet(27/34 Pages) LINER

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LTM4646

4646f

For more information www.linear.com/LTM4646

the above ambient temperature multiplicative factors. The

printed circuit board is a 1.6mm thick four layer board

with two ounce copper for the two outer layers and one

ounce copper for the two inner layers.

Use a separated SGND ground copper area for compo-

nents connected to signal pins. Connect the SGND to GND

underneath the unit.

• For parallel modules, tie the VOUT, VFB, and COMP

pins together. Use an internal layer to closely connect

these pins together. The TRACK/SS pin can be tied a

common capacitor for regulator soft-start.

• Bring out test points on the signal pins for monitoring.

Figures 17a and 17b give a good example of the recom-

mended layout.

Layout Checklist/Example

The high integration of LTM4646 makes the PCB board

layout very simple and easy. However, to optimize its

electrical and thermal performance, some layout consid-

erations are still necessary.

• Use large PCB copper areas for high current paths,

including VIN, GND, VOUT1 and VOUT2. It helps to mini-

mize the PCB conduction loss and thermal stress.

• Place high frequency ceramic input and output capac-

itors next to the VIN, GND and VOUT pins to minimize

high frequency noise.

• Place a dedicated power ground layer underneath the

unit.

• To minimize the via conduction loss and reduce mod-

ule thermal stress, use multiple vias for interconnec-

tion between top layer and other power layers.

• Do not put vias directly on the pads, unless they are

capped or plated over.

APPLICATIONS INFORMATION

Figure 17. Recommended PCB Layout

GND

VOUT2

GND

VOUT1

VIN2

(a)

TOP LAYER

15mm x 11.25mm x 5.01mm

4646 F17a

GND

VOUT2

GND

VOUT1

VIN2

(b)

BOTTOM LAYER

15mm x 11.25mm x 5.01mm

4646 F17b

LTM4645 Datasheet(PDF) 27 Page - Linear Technology

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