AD590 Просмотр технического описания (PDF) - Analog Devices

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AD590

2-Terminal IC Temperature Transducer

Analog Devices 

AD590

NONLINEARITY

Nonlinearity as it applies to the AD590 is the maximum

deviation of current over temperature from a best-fit straight

line. The nonlinearity of the AD590 over the −55°C to +150°C

range is superior to all conventional electrical temperature

sensors such as thermocouples, RTDs, and thermistors. Figure 12

shows the nonlinearity of the typical AD590K from Figure 11.

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 12. Nonlinearity

Figure 13 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

OP177

AD590

100mV/°C

VT = 100mV/°C

V–

Figure 13. 2-Temperature Trim

Data Sheet

2

0

–2

–55

0

100

150

TEMPERATURE (°C)

Figure 14. 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 11).

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 15 is a

model of the AD590 that demonstrates these characteristics.

TJ θJC TC θCA

+

P

CCH

CC

TA

–

Figure 15. Thermal Circuit Model

Rev. G | Page 8 of 16

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