CDCE62002 datasheet(38/49 Pages) TI

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Device Power Calculation and Thermal Management

No Solder Mask

Internal

Power

Plane

Component Side

Back Side

Solder Mask

Thermal Vias

QFN-32

Thermal Slug

(package bottom)

Thermal

Dissipation

Pad (back side)

Internal

Ground

Plane

CDCE62002 Power Supply Bypassing – Recommended Layout

Component & Back Side

Component Side

Only

CDCE62002

SCAS882A – JUNE 2009 – REVISED JULY 2009.............................................................................................................................................................. www.ti.com

The CDCE62002 is a high performance device; therefore careful attention must be paid to device configuration

and printed circuit board layout with respect to power consumption. Table 21 provides the power consumption for

the individual blocks within the CDCE62002. To estimate total power consumption, calculate the sum of the

products of the number of blocks used and the power dissipated of each corresponding block.

Table 21. CDCE62002 Power Consumption

INTERNAL BLOCK

POWER DISSIPATED

NUMBER OF BLOCKS

(Power at 3.3V)

PER BLOCK

PER DEVICE

Input Circuit

PLL and VCO Core

333

Output Divider

Output Buffer ( LVPECL)

150

Output Buffer (LVDS)

Output Buffer (LVCMOS)

This power estimate determines the degree of thermal management required for a specific design. Observing

good thermal layout practices enables the thermal pad on the backside of the QFN-32 package to provide a

good thermal path between the die contained within the package and the ambient air. This thermal pad also

serves as the ground connection the device; therefore, a low inductance connection to the ground plane is

essential.

Figure 30. CDCE62002 Recommended PCB Layout

Figure 31 shows a conceptual layout focusing on power supply bypass capacitor placement. If the capacitors are

mounted on the back side, 0402 components can be employed; however, soldering to the Thermal Dissipation

Pad can be difficult. If the capacitors are mounted on the component side, 0201 components must be used to

facilitate signal routing. In either case, the connections between the capacitor and the power supply terminal on

the device must be kept as short as possible.

Figure 31. CDCE62002 Power Supply Bypassing

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