LTM4650 datasheet(28/38 Pages) AD

28 / 38 page

LTM4652

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

The derived thermal resistances in Table 2 to Table 4 for

the various conditions can be multiplied by the calcu-

lated power loss as a function of ambient temperature to

derive temperature rise above ambient, thus maximum

junction temperature. Room temperature power loss can

be derived from the efficiency curves and adjusted with

the above ambient temperature multiplicative factors. The

printed circuit board is a 1.6mm thick four layer board

with two ounce copper for all four layers. The PCB dimen-

sions are 101mm × 114mm. The BGA heat sinks are listed

in Table 5.

Layout Checklist/Example

The high integration of LTM4652 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 min-

imize the PCB conduction loss and thermal stress.

• Place high frequency ceramic input and output capac-

itors next to the VIN, PGND 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 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.

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

together. Use an internal layer to closely connect these

pins together. The TRACK pin can be tied a common

capacitor for regulator soft-start.

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

Figure 30givesagoodexampleoftherecommended layout.

Figure 30. Recommended PCB Layout

VOUT1

VOUT2

GND

SGND

CNTRL

4652 F30

GND

VIN

11 12

COUT1

COUT2

CIN1

CIN2

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