Wavelength Electronics WHY5640, Datasheet And Operating Manual

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WHY5640 TEMPERATURE CONTROLLER
Configuration for External Setpoint Voltage with
Thermistor Sensors - Pins 1, 6, & 7
Use an external setpoint voltage to control the desired
operating temperature of the WHY5640 with NTC (Negative
Temperature Coefficient) thermistors. Figure 16 illustrates
an effective circuit. This setup is useful when operating the
WHY5640 in a DAC controlled system.
+0.5V
SENSOR BRIDGE AMPLIFIER
R
T
1 7 6
THERMISTOR
V
IN
+
-
1/2LM358
AGND
SENS
ERR
WHY5640
R
1
Figure 16. External Voltage Control Using Thermistor
Sensors
Equation 7 illustrates how to determine the setpoint voltage,
V
IN
, given a desired thermistor resistance (temperature).
(8)
Resistor, R
1
, is a fixed resistance value that can be used
to scale or adjust the setpoint voltage, V
IN
, allowing control
above and below the ambient temperature. In most
applications select resistor R
1
equal to two times the desired
operating thermistor resistance, R
T
. For example, for a
10 kΩ thermistor operating at 25ºC, choose R
1
to be 20 kΩ.
NOTE: Pin 9 (OUTA) is the heating current sink and
Pin 13 (OUTB) is the cooling current sink.
Figure 17 demonstrates an example of how to use an
external voltage setpoint to control a 10 kΩ thermistor from
a range of 20 kΩ to 0 kΩ.
V
IN
= 0.5 –
R
T
2R
1
+0.5V
SENSOR BRIDGE AMPLIFIER
R
T
1
7 6
THERMISTOR
V
IN
+
-
1/2LM358
AGND
SENS
ERR
WHY5640
20 kΩ
10 kΩ
Figure 17. Example Using a 10kΩ Thermistor with External
Voltage Control
Configuration for External Setpoint Voltage with RTD
Sensors - Pins 1, 6, & 7
Use an external setpoint voltage to control the desired
operating temperature of the WHY5640 with PTC (Positive
Temperature Coefficient) RTDs. This setup is useful
when operating the WHY5640 in a DAC controlled system.
Figure 18 illustrates an effective circuit.
Figure 18. External Voltage Control Using RTD Sensors
Equation 8 illustrates how to determine the setpoint voltage,
V
IN
, given a desired RTD resistance (temperature).
(9)
+0.5V
SENSOR BRIDGE AMPLIFIER
R
RTD
1
7 6
RTD
V
IN
+
-
1/2LM358
AGND
SENS
ERR
WHY5640
R
2
V
IN
= 0.5 – R RTD
2R
2