FUNCTIONAL BLOCK DIAGRAM
REV. B
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use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
a
Thermocouple Conditioner and
Setpoint Controller
AD596*/AD597*
FEATURES
Low Cost
Operates with Type J (AD596) or Type K (AD597)
Thermocouples
Built-In Ice Point Compensation
Temperature Proportional Operation – 10 mV/8C
Temperature Setpoint Operation – ON/OFF
Programmable Switching Hysteresis
High Impedance Differential Input
GENERAL DESCRIPTION
The AD596/AD597 is a monolithic temperature setpoint con-
troller that has been optimized for use at elevated temperatures
such as those found in oven control applications. The device
cold junction compensates and amplifies a type J or K thermo-
couple input to derive an internal signal proportional to tem-
perature. The internal signal is then compared with an externally
applied setpoint voltage to yield a low impedance switched output
voltage. Dead-Band or switching hysteresis can be programmed
using a single external resistor. Alternately, the AD596/AD597 can
be configured to provide a voltage output (10 mV/°C) directly from
a type J or K thermocouple signal. It can also be used as a stand-
alone voltage output temperature sensor.
The AD596/AD597 can be powered with a single supply from
+5 V to +30 V, or dual supplies up to a total span of 36 V.
Typical quiescent supply current is 160 µA, which minimizes
self-heating errors.
The AD596/AD597 H package option includes a thermocouple
failure alarm that indicates an open thermocouple lead when
operated in the temperature proportional measurement mode.
The alarm output has a flexible format which can be used to
drive relays, LEDs or TTL logic.
The device is packaged in a reliability qualified, cost effective
10-pin metal can or SOIC and is trimmed to operate over an
ambient temperature range from +25°C to +100°C. Operation
over an extended ambient temperature range is possible with
slightly reduced accuracy. The AD596 will amplify thermo-
couple signals covering the entire –200°C to +760°C tempera-
ture range recommended for type J thermocouples while the
AD597 can accommodate –200°C to +1250°C type K inputs.
The AD596/AD597 has a calibration accuracy of ±4°C at an
ambient temperature of 60°C and an ambient temperature
stability specification of 0.05°C/°C from +25°C to +100°C. If
higher accuracy, or a lower ambient operating temperature is
required, either the AD594 (J thermocouple) or AD595 (K
thermocouple) should be considered.
*Protected by U.S. Patent No. 4,029,974.
PRODUCT HIGHLIGHTS
1. The AD596/AD597 provides cold junction compensation
and a high gain amplifier which can be used as a setpoint
comparator.
2. The input stage of the AD596/AD597 is a high quality in-
strumentation amplifier that allows the thermocouple to float
over most of the supply voltage range.
3. Linearization not required for thermocouple temperatures
close to 175°C (+100°C to +540°C for AD596).
4. Cold junction compensation is optimized for ambient tem-
peratures ranging from +25°C to +100°C.
5. In the stand-alone mode, the AD596/AD597 produces an
output voltage that indicates its own temperature.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 1998
TO-100
+
–
G
FB
V
OUT
+ALM
+IN
V–
V+
A
+
ICE
POINT
COMP
+
AD596/
AD597
–ALM
–IN
HYS
GND
+
–
G
SOIC
+IN
–IN
TOP VIEW
(Not to Scale)
AD597
G
–
+
+
G
–
+
A
+
ICE POINT
COMP
HYS
V+
GND
V
OUT
V–
FB
1
2
3
45
6
7
8
