TL074 datasheet(22/39 Pages) TI2

22 / 39 page

10.0

1.0

0.1

12 14 16 18 20 22

24 26

(V+)

(V )(V)

OUT VOUT -

SAFEOPERATINGAREAATROOMTEMPERATURE

Copper,Soldered

withoutForcedAir

Copper,Soldered

with200LFMAirflow

10.0

1.0

0.1

0.01

12 14 16 18 20 22

24 26

SAFEOPERATINGAREAATVARIOUSAMBIENTTEMPERATURES

(PowerPADSoldered)

T = 40 C

T =0 C

T =+25 C

T =+85 C

T =+125 C

(V+)

(V )(V)

- OUT VOUT -

OPA564

SBOS372E

– OCTOBER 2008 – REVISED JANUARY 2011

www.ti.com

POWER DISSIPATION AND SAFE

Once

the

heatsink

area

has

been

selected,

OPERATING AREA

worst-case load conditions should be tested to ensure

proper thermal protection.

Power dissipation depends on power supply, signal,

and load conditions. For dc signals, power dissipation

space

is equal to the product of output current (IOUT) and the

voltage

across

the

conducting

output

transistor

[(V+)

– VOUT when sourcing; VOUT – (V–) when

sinking].

Dissipation

with

signals

lower.

Application Bulletin AB-039, Power Amplifier Stress

and Power Handling Limitations (SBOA022, available

for download from www.ti.com) explains how to

calculate or measure power dissipation with unusual

signals and loads.

Figure 45 shows the safe operating area at room

temperature with various heatsinking efforts. Note

that the safe output current decreases as (V+)

– VOUT

or VOUT – (V–) increases. Figure 46 shows the safe

operating area at various temperatures with the

PowerPAD being soldered to a 2oz copper pad.

The power that can be safely dissipated in the

package is related to the ambient temperature and

Figure 45. Safe Operating Area at Room

the heatsink design. The PowerPAD package was

Temperature

specifically designed to provide excellent power

dissipation, but board layout greatly influences the

heat dissipation of the package. Refer to the

Thermally-Enhanced PowerPAD Package section for

further details.

The relationship between thermal resistance and

power dissipation can be expressed as:

TJ = TA + TJA

TJA = PD × qJA

Combining these equations produces:

TJ = TA + PD × qJA

where:

TJ = Junction temperature (°C)

TA = Ambient temperature (°C)

qJA = Junction-to-ambient thermal resistance (°C/W)

PowerPAD soldered to a 2oz copper pad.

PD = Power dissipation (W)

Figure 46. Safe Operating Area at Various

Ambient Temperatures

To determine the required heatsink area, required

power dissipation should be calculated and the

relationship between power dissipation and thermal

resistance

should

considered

minimize

shutdown conditions and allow for proper long-term

operation (junction temperature of +85

°C or less).

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