Data Sheet

AD590

Rev. G | Page 9 of 16

the thermal resistance between the case and the surroundings

and is determined by the characteristics of the thermal

connection. Power source P represents the power dissipated

(1)

thermal media for both the H and F packages. The heat sink

used was a common clip-on. Using Equation 1, the temperature

rise of an AD590 H package in a stirred bath at 25°C, when

driven with a 5 V supply, is 0.06°C. However, for the same

conditions in still air, the temperature rise is 0.72°C. For a given

supply voltage, the temperature rise varies with the current and

is PTAT. Therefore, if an application circuit is trimmed with the

sensor in the same thermal environment in which it is used, the

scale factor trim compensates for this effect over the entire

temperature range.

Table 4. Thermal Resistance

(°C/Watt)

Medium

H

F

H

F

Aluminum Block

30

10

0.6

0.1

42

60

1.4

0.6

With Heat Sink

45

–

5.0

–

Without Heat Sink

115

190

13.5

10.0

Still Air

With Heat Sink

191

–

108

–

Without Heat Sink

480

650

60

30

instantaneous temperature change.

The time response of the AD590 to a step change in

temperature is determined by the thermal resistances and the

medium, because it includes anything that is in direct thermal

contact with the case. The single time constant exponential

curve of Figure 16 is usually sufficient to describe the time

response, T (t). Table 4 shows the effective time constant, τ, for

several media.

Figure 16. Time Response Curve



4



TIME