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AD590JRZ-RL

2-Terminal IC Temperature Transducer

Analog Devices 

AD590

1.6

0.8

0

0.8°C

MAX

–0.8

0.8°C MAX

0.8°C

MAX

–1.6

–55

150

TEMPERATURE (°C)

Figure 11. Nonlinearity

Figure 12 shows a circuit in which the nonlinearity is the major

contributor to error over temperature. The circuit is trimmed

by adjusting R1 for a 0 V output with the AD590 at 0°C. R2 is

then adjusted for 10 V output with the sensor at 100°C. Other

pairs of temperatures can be used with this procedure as long as

they are measured accurately by a reference sensor. Note that

for 15 V output (150°C), the V+ of the op amp must be greater

than 17 V. Also, note that V− should be at least −4 V; if V− is

ground, there is no voltage applied across the device.

15V

AD581

R1

35.7kΩ 2kΩ

R2

97.6kΩ 5kΩ

30pF

27kΩ

AD707A

AD590

100mV/°C

VT = 100mV/°C

V–

Figure 12. 2-Temperature Trim

2

0

–2

–55

0

100

150

TEMPERATURE (°C)

Figure 13. Typical 2-Trim Accuracy

VOLTAGE AND THERMAL ENVIRONMENT EFFECTS

The power supply rejection specifications show the maximum

expected change in output current vs. input voltage changes.

The insensitivity of the output to input voltage allows the use of

unregulated supplies. It also means that hundreds of ohms of

resistance (such as a CMOS multiplexer) can be tolerated in

series with the device.

It is important to note that using a supply voltage other than 5 V

does not change the PTAT nature of the AD590. In other words,

this change is equivalent to a calibration error and can be

removed by the scale factor trim (see Figure 10).

The AD590 specifications are guaranteed for use in a low

thermal resistance environment with 5 V across the sensor.

Large changes in the thermal resistance of the sensor’s environment

change the amount of self-heating and result in changes in the

output, which are predictable but not necessarily desirable.

The thermal environment in which the AD590 is used

determines two important characteristics: the effect of self-

heating and the response of the sensor with time. Figure 14 is a

model of the AD590 that demonstrates these characteristics.

TJ θJC TC θCA

+

P

CCH

CC

TA

–

Figure 14. Thermal Circuit Model

As an example, for the TO-52 package, θJC is the thermal

resistance between the chip and the case, about 26°C/W. θCA is

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

on the chip. The rise of the junction temperature, TJ, above the

ambient temperature, TA, is

TJ − TA = P(θJC + θCA)

(1)

Table 4 gives the sum of θJC and θCA for several common

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.

Rev. E | Page 8 of 16

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