P = V x 2I

= 24 x 2 x (6.5 x 10 )

= 312mW

Q

S

q

-3

+

-

R7

2k

1:1

R6

2k

Twisted

Pair Line

R5

2k

100

1/2

LM7372

+

-

R9

50

R8

50

C7

20uF

C6

0.1uF

+

1/2

LM7372

C1

0.1uF

R3

5.1k

R4

5.1k

R1

10.2k

R2

10.2k

C3

47uF

+

3

5

4

14

13

12

11

6

C2

0.1uF

LM7372

SNOS926F – MAY 1999 – REVISED SEPTEMBER 2014

www.ti.com

Typical Application (continued)

Figure 24. Single Supply Application (16-Pin SOIC)

8.3 Application Details

Several factors contribute to power dissipation and consequently higher semiconductor junction temperatures.

Understanding these factors is necessary if the LM7372 is to perform to the desired specifications. Since

different applications will have different dissipation levels and since there are various possible compromises

between the ways these factors will contribute to the total junction temperature, this section will examine the

typical application shown in Figure 24 as an example, and offer solutions when encountering excessive junction

temperatures.

There are two major contributors to the internal power dissipation. The first is the product of the supply voltage

and the LM7372 quiescent current when no signal is being delivered to the external load, and the second is the

additional power dissipated while delivering power to the external load. For low frequency (<1MHz) applications,

the LM7372 supply current specification will suffice to determine the quiescent power dissipation (see High

Frequency/Large Signal Swing Considerations for cases where the frequency range exceeds 1MHz and the

LM7372 supply current increases). The LM7372 quiescent supply current is given as 6.5 mA per amplifier, so

with a 24-V supply, the power dissipation is:

where

•

(1)

This is already a high level of internal power dissipation, and in a small surface mount package with a thermal

junction temperature 140°C/W x 0.312W = 43.7°C above the ambient temperature. A similar calculation using the

worst case maximum supply current specification of 8.5 mA per amplifier at an 85°C ambient will yield a power

dissipation of 456 mW with a junction temperature of 149°C, perilously close to the maximum permitted junction

temperature of 150°C.

The second contributor to high junction temperature is the additional power dissipated internally when power is

being delivered to the external load. This cause of temperature rise can be more difficult to calculate, even when

the actual operating conditions are known.

14

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