LTM4643 datasheet(24/30 Pages) AD

24 / 30 page

LTM4638

Rev. C

For more information www.analog.com

APPLICATIONS INFORMATION

curves in the Typical Performance Characteristics section

andadjustedwiththeaboveambienttemperaturemultipli-

cative factors. The printed circuit board is a 1.6mm thick

4-layer board with two ounce copper for the two outer

layers and one ounce copper for the two inner layers. The

PCB dimensions are 95mm × 76mm.

Safety Considerations

The LTM4638 modules do not provide galvanic isolation

from VIN to VOUT. There is no internal fuse. If required,

a slow blow fuse with a rating twice the maximum input

current needs to be provided to protect each unit from

catastrophic failure. The device does support thermal

shutdown and over current protection.

Layout Checklist/Example

The high integration of LTM4638 makes the PCB board

layoutverysimpleandeasy.However,tooptimizeitselectri-

cal and thermal performance, some layout considerations

are still necessary.

• Use large PCB copper areas for high current paths,

including VIN, GND and VOUT. It helps to minimize the

PCB conduction loss and thermal stress.

• Place high frequency ceramic input and output capaci-

tors next to the VIN, PGND and VOUT pins to minimize

high frequency noise.

• Place a dedicated power ground layer underneath the

unit.

Figure 22. Recommended PCB Layout

VIN

VOUT

4638 F22

GND

• To minimize the via conduction loss and reduce module

thermal stress, use multiple vias for interconnection

between top layer and other power layers.

• Do not put via directly on the pad, unless they are

capped or plated over.

• Use a separated SGND ground copper area for com-

ponents connected to signal pins. Connect the SGND

to GND underneath the unit.

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

• KeepseparationbetweenCLKIN,CLKOUTandFREQpin

traces to minimize possibility of noise due to crosstalk

between these signals.

Figure22givesagoodexampleoftherecommendedlayout.

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