THS4031 datasheet(30/47 Pages) TI

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D +

MAX

–T

Where:

= Maximum power dissipation of THS403x IC (watts)

TMAX = Absolute maximum operating junction temperature (125°C)

= Free-ambient air temperature (

°C)

θJA = θJC + θCA

θJC = Thermal coefficient from junction to case

θCA = Thermal coefficient from case to ambient air (°C/W)

MAXIMUMPOWERDISSIPATION

AMBIENTTEMPERATURE

0.5

1.5

2.5

-40

-20

100

TA-Free AirTemperature-°C

DGNPackage

=58.4ºC/W2oz.

TraceandCopperPad

WithSolder

T =130ºC

DGNPackage

=158.4ºC/W2oz.

TraceandCopperPad

WithoutSolder

SOICPackage

High-KTestPCB

=98ºC/W

SOICPackage

High-KTestPCB

=166.7ºC/W

THS4031

THS4032

SLOS224G – JULY 1999 – REVISED MARCH 2010

www.ti.com

The actual thermal performance achieved with the THS403xDGN in its PowerPAD™ package depends on the

application. In the example above, if the size of the internal ground plane is approximately 3 inches × 3 inches

(7,62 cm × 7,62 cm), then the expected thermal coefficient, qJA, is about 58.4°C/W. For comparison, the

non-PowerPAD™ version of the THS403x IC (SOIC) is shown. For a given qJA, the maximum power dissipation

is shown in Figure 62 and is calculated by the following formula:

(3)

Results are with no air flow and PCB size = 3”× 3” (7,62 cm x 7,62 cm)

Figure 62. Maximum Power Dissipation vs Free-Air Temperature

More complete details of the PowerPAD installation process and thermal management techniques can be found

in the Texas Instruments technical brief, PowerPAD™ Thermally-Enhanced Package (SLMA002). This document

can be found at the TI web site (www.ti.com) by searching on the key word PowerPAD. The document can also

be ordered through your local TI sales office. Refer to literature number SLMA002 when ordering.

The next thing to be considered is package constraints. The two sources of heat within an amplifier are quiescent

power and output power. The designer should never forget about the quiescent heat generated within the device,

especially multiamplifier devices. Because these devices have linear output stages (Class A-B), most of the heat

dissipation is at low output voltages with high output currents. Figure 63 to Figure 66 shows this effect, along with

the quiescent heat, with an ambient air temperature of 50°C. When using VCC = ±5 V, heat is generally not a

problem, even with SOIC packages. But, when using VCC = ±15 V, the SOIC package is severely limited in the

amount of heat it can dissipate. The other key factor when looking at these graphs is how the devices are

mounted on the PCB. The PowerPAD™ devices are extremely useful for heat dissipation. But, the device should

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