THS4501CD datasheet(31/37 Pages) TI

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THS4500

THS4501

SLOS350D − APRIL 2002 − REVISED JANUARY 2004

www.ti.com

Place five holes in the area of the thermal pad. These

holes should be 13 mils in diameter. Keep them small

so that solder wicking through the holes is not a

problem during reflow.

Additional vias may be placed anywhere along the

thermal plane outside of the thermal pad area. This

helps dissipate the heat generated by the THS4500

family IC. These additional vias may be larger than the

13-mil diameter vias directly under the thermal pad.

They can be larger because they are not in the thermal

pad area to be soldered so that wicking is not a

problem.

Connect all holes to the internal ground plane.

When connecting these holes to the ground plane, do

not use the typical web or spoke via connection

methodology. Web connections have a high thermal

resistance connection that is useful for slowing the

heat transfer during soldering operations. This makes

the soldering of vias that have plane connections

easier. In this application, however, low thermal

resistance is desired for the most efficient heat

transfer. Therefore, the holes under the THS4500

family PowerPAD package should make their

connection to the internal ground plane with a

complete connection around the entire circumference

of the plated-through hole.

The top-side solder mask should leave the terminals

of the package and the thermal pad area with its five

holes exposed. The bottom-side solder mask should

cover the five holes of the thermal pad area. This

prevents solder from being pulled away from the

thermal pad area during the reflow process.

Apply solder paste to the exposed thermal pad area

and all of the IC terminals.

With these preparatory steps in place, the IC is simply

placed in position and run through the solder reflow

operation

any

standard

surface-mount

component. This results in a part that is properly

installed.

POWER DISSIPATION AND THERMAL

CONSIDERATIONS

The THS4500 family of devices does not incorporate

automatic thermal shutoff protection, so the designer must

take care to ensure that the design does not violate the

absolute maximum junction temperature of the device.

Failure may result if the absolute maximum junction

temperature of 150

°C is exceeded. For best performance,

design for a maximum junction temperature of 125

°C.

Between 125

°C and 150°C, damage does not occur, but

the performance of the amplifier begins to degrade.

The thermal characteristics of the device are dictated by

the package and the PC board. Maximum power

dissipation for a given package can be calculated using the

following formula.

Dmax +

Tmax–TA

Where:

PDmax is the maximum power dissipation in the amplifier (W).

Tmax is the absolute maximum junction temperature (°C).

TA is the ambient temperature (°C).

θJA = θJC + θCA

θJC is the thermal coefficient from the silicon junctions to the

case (

°C/W).

θCA is the thermal coefficient from the case to ambient air

(

°C/W).

(28)

For systems where heat dissipation is more critical, the

THS4500 family of devices is offered in an 8-pin MSOP

with PowerPAD. The thermal coefficient for the MSOP

PowerPAD package is substantially improved over the

traditional SOIC. Maximum power dissipation levels are

depicted in the graph for the two packages. The data for

the DGN package assumes a board layout that follows the

PowerPAD layout guidelines referenced above and

detailed in the PowerPAD application notes in the

Additional Reference Material section at the end of the

data sheet.

1.5

−40

−20

2.5

3.5

TA − Ambient Temperature − °C

8-Pin DGN Package

θJA = 170°C/W for 8-Pin SOIC (D)

θJA = 58.4°C/W for 8-Pin MSOP (DGN)

ΤJ = 150°C, No Airflow

Figure 117. Maximum Power Dissipation vs

Ambient Temperature

0.5

8-Pin D Package

When determining whether or not the device satisfies the

maximum power dissipation requirement, it is important to

not only consider quiescent power dissipation, but also

dynamic power dissipation. Often times, this is difficult to

quantify because the signal pattern is inconsistent, but an

estimate of the RMS power dissipation can provide

visibility into a possible problem.

THS4501CD Datasheet(PDF) 31 Page - Texas Instruments

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