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WHY5640 SUBMINIATURE TEMPERATURE CONTROLLER
January 8, 2002
WHY5640
Subminiature Temperature Controller
(BOTTOM VIEW)
GENERAL DESCRIPTION:
The WHY5640 is a general purpose analog PI (Proportional, Integral) control loop for use in thermoelectric or resistive heater temperature control applications. The WHY5640 maintains precision temperature regulation using an active resistor bridge circuit that operates directly with thermistors or RTD temperature sensors. Supply up to 2 Amps of heat and cool current to your thermoelectric from a single +5 Volt power supply. Connect two or more WHY5640 units together and drive higher output currents.
FEATURES:
* + 5 to + 28V Operation * Low Cost * 0.008 C Stability (typical) * PI Temperature Control * High 2 Amps Output Current * Control Above and Below Ambient * Small Package Size
Figure 1
Top View Pin Layout and Descriptions
TOP VIEW
Buffer B Thermoelectric Output B Control Electronics Supply Ground Power Drive Supply Ground Power Drive Supply Input Thermoelectric Output A Control Electronics Supply Input
14 13 12 11 10 9 8
BUFB OUTB CGND PGND VS OUTA VDD
AGND LIMB LIMA BUFA PI ERR SENS
1 2 3 4 5 6 7
Analog Ground Limit B Limit A Buffer A Gain/Integrator Common Temperature Error Output Sensor and Setpoint Input
IF YOU ARE UPGRADE FROM THE WHY5640 to the WTC3243: The position of Pin 1 on the WHY5640 is reversed (or mirrored) relative to the position of Pin 1 on the WTC3243.
(c) 2001, 2003 WHY5640-00400-A Rev C www.teamwavelength.com
WHY5640
(c) 2001, 2003
R B
WHY5640 SHOWN WITHIN DASHED LINES
BLOCK DIAGRAM External Connections with Thermistor Operation
R A
THERMISTOR
R L V S L C
R T
SETPOINT TRIMPOT R S
R
G
V
DD
THERMOELECTRIC COOLER
AGND
5 3 4 9 13 2 10 14
SENS
ERR
PI OUTA OUTB BUFB LIMB VS
LIMA
BUFA
PGND
11
CGND
12
VDD
8
1
7
6
Voltage Regulator
COOL
HEAT
+1V +0.5 V Ref . Voltages
WHY5640-00400-A Rev B
+1V +1V
+0.5 V
SENSOR BRIDGE AMPLIFIER
PROPORTIONAL/INTEGRAL CONTROL LOOP
VOLTAGE TO CURRENT CONVERTOR H-BRIDGE POWER STAGE
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PAGE 2
WHY5640
PAGE 3
ELECTRICAL AND OPERATING SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
RATING Supply Voltage 1 (Voltage on Pin 8) Supply Voltage 2 (Voltage on Pin 10) Output Current (See SOA Chart) Power Dissipation, TAMBIENT = +25C Operating Temperature, case Storage Temperature
SYMBOL VALUE
VDD VS IS PMAX TOPR TSTG +5 to +30 +3 to +30 2.5 9 -40 to +85 -65 to +150
UNIT
Volts DC Volts DC Amperes Watts C C
PARAMETER
TEMPERATURE CONTROL Short Term Stability, 1 hour Long Term Stability, 24 hour Setpoint vs. Actual Temp Accuracy Control Loop P (Proportional Gain) I (Integrator Time Constant) OUTPUT Current, peak, see SOA chart
TEST CONDITIONS
MIN
TYP
0.005 0.008 <1%
MAX
0.01 0.01
UNITS
C C
TSET = 25C using 10 k thermistor 0.001 TSET = 25C using 10 k thermistor 0.003 TSET = 25C using 10 k thermistor P 1 1
PI 100 10 A/V Sec.
2.0
2.2
2.5
Amps Volts Volts Volts
Compliance Voltage, Pin 9 to Pin 13 Full Temp. Range, IS = 100 mA Compliance Voltage, Pin 9 to Pin 13 Full Temp. Range, IS = 1 Amp Compliance Voltage, Pin 9 to Pin 13 Full Temp. Range, IS = 2 Amps POWER SUPPLY Voltage, VS Voltage, VDD Current, VS supply, Quiescent Current, VDD supply, Quiescent INPUT Offset Voltage, initial Bias Current Offset Current Common Mode Range Common Mode Rejection Power Supply Rejection Input Impedence THERMAL Heatspreader Temperature Rise Heatspreader Temperature Rise Heatspreader Temperature Rise TAMBIENT =25C With WHS302 Heatsink, WTW002 Thermal Washer With WHS302 Heatsink, WTW002 Thermal Washer, and 3.5 CFM Fan (c) 2001, 2003 WHY5640-00400-A Rev B Pin 5 and 7 Pins 5 and 7, TAMBIENT = 25C Pins 5 and 7, TAMBIENT = 25C Pins 5 and 7, Full Temp. Range Full Temperature Range Full Temperature Range
| VS - 1.7 | | VS - 1.4 | | VS - 2.2 | | VS - 2.0 | | VS - 3.3 | | VS - 2.6 |
5 5 45 10
28 28 90 15
Volts Volts mA mA
1 20 2 0 60 60 85 80 500
2 50 10
mV nA nA dB dB k
VDD-1.5 V
28 18 3.1
30 21.5 3.4
33 25 3.9
C/W C/W C/W
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WHY5640
PAGE 4
PIN DESCRIPTIONS
PIN NO. PIN
1
NAME
FUNCTION
The analog ground connection is internally connected to Pins 11 and 12 (the power supply ground connections) and eliminates grounds loops for stable operation of the sensor amplifier bridge and limit current resistors.
AGND Analog Ground
2
LIMB
LIMIT B
A resistor connected between Pin 2 (LIMB) and Pin 1 (AGND) limits the output current drawn off the Pin 10 (VS) supply input and into Pin 13 (OUTB).
3
LIMA
LIMIT A
A resistor connected between Pin 3 (LIMA) and Pin 1 (AGND) limits the output current drawn off the Pin 10 (VS) supply input and into Pin 9 (OUTA). Also connect integrator capacitor C L to Pin 3 (LIMA) when operating the WHY5640 as a standard PI controller.
4 5 6 7 8 9
BUFA BUFFER A PI ERR
Connect Pin 4 (BUFA) to Pin 3 (LIMA) of another WHY5640 when operating the devices in a master/slave configuration.
Proportional Gain/ Integrator When using the WHY5640 as a standard PI controller, connect Common Temperature Error Input one end of the proportional gain resistors RG and R L to Pin 5 (PI). When using the WHY5640 as a standard PI controller, connect one end of the proportional gain resistor RG to Pin 6 (ERR). Pin 7 (SENS) is the common sensor bridge amplifier connection for the sensor, RT, and setpoint, RS, resistors. Power supply input for the WHY5640's internal control electronics. Supply range input for this pin is +5 to +28 Volts DC. Connect Pin 9 (OUTA) to the negative terminal on your thermoelectric when controlling temperature with Negative Temperature Coefficient thermistors. Connect Pin 9 (OUTA) to the positive thermoelectric terminal when using Positive Temperature Coefficient RTDs.
SENS Sensor and Setpoint Input VDD Control Electronics Supply Input OUTA Thermoelectric Output A
10
VS
Power Drive Supply Input
Provides power to the WHY5640 H-Bridge Power Stage. Supply range input for this pin is +5 to +28 Volts DC. The maximum current drain on this terminal should not exceed 2.5 Amperes.
11
PGND Power Drive Supply Ground
Connect the VS power supply ground connection to Pin 11 (PGND). Pin 11 (PGND) and Pin 12 (CGND) are internally connected.
12 13
CGND Control Electronics Supply Ground OUTB Thermoelectric Output B
Connect the VDD supply ground connection to Pin 12 (CGND). Pin 12 (CGND) and Pin 11 (PGND) are internally connected. Connect Pin 13 (OUTB) to the positive terminal on your thermoelectric when controlling temperature with Negative Temperature Coefficient thermistors. Connect Pin 13 (OUTB) to the negative thermoelectric terminal when using Positive Temperature Coefficient RTDs.
14
BUFB Buffer B
Connect Pin 14 (BUFB) to Pin 2 (LIMB) of another WHY5640 when operating the devices in a master/slave configuration.
IF YOU ARE UPGRADE FROM THE WHY5640 to the WTC3243: The position of Pin 1 on the WHY5640 is reversed (or mirrored) relative to the position of Pin 1 on the WTC3243.
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WHY5640
TYPICAL PERFORMANCE GRAPHS
PAGE 5
Caution:
Do not exceed the Safe Operating Area (SOA). Exceeding the SOA voids the warranty.
To determine if the operating parameters fall within the SOA of the device, the maximum voltage drop across the controller and the maximum current must be plotted on the SOA curves. These values are used for the example SOA determination: Vs= 12 volts Vload = 5 volts ILoad = 1 amp Follow these steps: 1. 2. 3. 4. 5. 6.
}
These values are determined from the specifications of the TEC or resistive heater
Determine the maximum voltage drop across the controller ,Vs-Vload, and mark on the X axis. (12volts - 5 volts = 7 volts, Point A) Determine the maximum current, ILoad, through the controller and mark on the Y axis: (1 amp, Point B) Draw a horizontal line through Point B across the chart. (Line BB) Draw a vertical line from Point A to the maximum current line indicated by Line BB. Mark Vs on the X axis. (Point C) Draw the Load Line from where the vertical line from point A intersects Line BB down to Point C.
Refer to the chart shown below and note that the Load Line is in the Unsafe Operating Areas for use with no heatsink (1) or the heatsink alone (2), but is outside of the Unsafe Operating Area for use with heatsink and Fan (3).
25 C Ambient 75 C Case
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WHY5640
SOA Charts for Customer Use:
PAGE 6
25 C Ambient 75 C Case
25 C Ambient 75 C Case
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PAGE 7
OPERATION
1. CONFIGURING HEATING AND COOLING CURRENT LIMITS
Refer to Table 1 to select appropriate resistor values for RA and RB.
Table 1
Current Limit Set Resistor vs Maximum Output Current
Setting Current Limits Independently Using Trimpots
The 5 k trimpots shown in Figure 3 adjust the maximum output currents from 0 to 2.3 Amps
Maximum Output Currents (Amps) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
Maximum Current Limit Set Output Resistor, Current (k) RA,R B (Amps) 1.60 1.69 1.78 1.87 1.97 2.08 2.19 2.31 2.44 2.58 2.72 2.88 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3
Current Limit Set Resistor, (k) RA,R B 3.05 3.23 3.43 3.65 3.88 4.13 4.42 4.72 5.07 5.45 5.88 6.36
Heat and Cool Current Limits
Figure 2
Fixed Heat and Cool Current Limits
Figure 3
Independently Adjustable Heat and Cool Current Limits
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PAGE 8
OPERATION
2. RESISTIVE HEATER TEMPERATURE CONTROL
The WHY5640 can operate resistive heaters by disabling the cooling output current. When using Resistive Heaters with NTC thermistors, connect Pin 3 (LIMA) to Pin 1 (AGND) with a 1.5 k resistor. Connect Pin 2 (LIMB) to Pin 1 (AGND) with a 1.5 k resistor when using RTD's, LM335 type and AD590 type temperature sensors with a resistive heater.
Figure 4
Disabling Output Current
3. DISABLING THE OUTPUT CURRENT
The output current can be enabled and disabled, as shown in Figure 5, using a DPDT (Double Pole-Double Throw) switch.
4. OPERATING WITH THERMISTOR SENSORS
Figure 5 illustrates how to connect the WHY5640 for operation with NTC (Negative Temperature Coefficient) thermistors. Connect a setpoint resistor, RS, (or trimpot) across Pins 1 (AGND) and 7 (SENS). Connect the thermistor, RT across Pins 6 (ERR) and 7 (SENS). Select setpoint resistor, RS, equal to the thermistor resistance at the desired operating temperature. When the setpoint resistor, RS, and thermistor, RT, are equal resistance values the Sensor Bridge Amplifier is balanced and the voltage on Pin 6 (ERR) will equal 1 Volt with reference to Pin 1 (AGND). If the setpoint resistor, RS, is larger than the thermistor resistance, RT, then the control loop will produce a cooling current since the temperature sensed by the thermistor is above (hotter than) the setpoint temperature. If the setpoint resistor, RS, is smaller than the thermistor resistance, RT, then the control loop will produce a heating current since the temperature sensed by the thermistor is below (cooler than) the setpoint temperature.
Figure 5
Thermistor Operation
SETPOINT TRIMPOT R S
THERMISTOR R T
1 AGND
7 SENS
6 ERR
WHY5640
+0.5 V SENSOR BRIDGE AMPLIFIER
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PAGE 9
OPERATION
5. USING AN EXTERNAL SETPOINT VOLTAGE WITH THERMISTOR SENSORS
Figure 6 illustrates how to connect the WHY5640 for operation with NTC (Negative Temperature Coefficient) thermistors using an external setpoint voltage to control the desired operating temperature. This setup is useful when operating the WHY5640 in a DAC controlled system. Equation 1 illustrates how to determine the setpoint voltage, VIN, given a desired thermistor resistance (temperature). Resistor, R1, is a fixed resistance value that can be used to scale or adjust the setpoint voltage, VIN, allowing control above and below the ambient temperature. In most applications select resistor R1 equal to two times the desired operating thermistor resistance, RT. NOTE: Pin 9 (OUTA) and Pin 13 (OUTB) must be swapped to maintain the proper heating and cooling current polarity through the thermoelectric. Pin 9 (OUTA) becomes the heating current sink and Pin 13 (OUTB) becomes the cooling current sink. Example 1 demonstrates how to use an external voltage setpoint to control a 10 k thermistor from a range of 20 k to 0 k. Figure 7 illustrates the setpoint voltage, VIN, versus thermistor resistance, RT, for Example 1.
Figure 6
External Voltage Control Using Thermistor Sensors
THERMISTOR R T
R
1
VIN -
+
1/2LM358
1 AGND
7 SENS
6 ERR
WHY5640
+0.5V SENSOR BRIDGE AMPLIFIER
Equation 1
Voltage Controlled Setpoint Using Thermistors
VIN = 0.5 -
RT 2R1
Figure 7 Example 1
Using a 10k Thermistor with External Voltage Control
10 k THERMISTOR R T 20 k
Setpoint Voltage (Volts)
Example 1 Setpoint Voltage vs Thermistor Resistance
VIN -
+
1/2LM358 1 AGND 7 SENS 6 ERR
0.5 0.4 0.3 0.2 0.1 0 10 k Thermistor
WHY5640
+0.5V SENSOR BRIDGE AMPLIFIER
0.00
5.00
10.00
15.00
20.00
Thermistor Resistance (k)
(c) 2001, 2003
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PAGE 10
OPERATION
6. OPERATING WITH RTD SENSORS
Figure 8 illustrates how to connect the WHY5640 for operation with PTC (Positive Temperature Coefficient) RTD sensors (Resistance Temperature Device). Resistors, R2, should be chosen large enough to prevent self heating of the RTD due to the current flowing through it.
Figure 8
RTD Operation
RTD R RTD R2 SETPOINT TRIMPOT R S R2
1
7 AGND WHY5640 SENS
6 ERR
Select setpoint resistor, RS, equal to the RTD resistance, RRTD, at the desired operating temperature. When the setpoint resistor, RS, and RTD, RRTD, are equal in value the Sensor Bridge Amplifier is balanced and the voltage on Pin 6 (ERR) will equal 1 Volt with reference to Pin 1 (AGND). If the setpoint resistor, RS, is larger than the RTD resistance, RRTD, then the control loop will produce a heating current since the temperature sensed by the RTD is below (cooler than) the setpoint temperature. If the setpoint resistor, RS, is smaller than the RTD resistance, RRTD, then the control loop will produce a cooling current since the temperature sensed by the RTD is above (hotter than) the setpoint temperature.
+0.5V SENSOR BRIDGE AMPLIFIER
Figure 9
External Voltage Control Using RTD Sensors
RTD
R
RTD
R
2
VIN -
+
1/2 LM358
1 AGND
7 SENS
6 ERR
7. USING AN EXTERNAL SETPOINT VOLTAGE WITH RTD SENSORS
Figure 9 illustrates how to connect the WHY5640 for operation with PTC (Positive Temperature Coefficient) RTD sensors using an external setpoint voltage to control the desired operating temperature. This setup is useful when operating the WHY5640 in a DAC controlled system. Equation 2 illustrates how to determine the set point voltage, VIN, given a desired RTD resistance (temperature). Resistor, R2, is a fixed resistance value that can be used to scale or adjust the setpoint voltage, VIN, allowing control above and below the ambient temperature. In most applications selecting resistor, R2, equal to two times the desired operating RTD resistance, RRTD.
WHY5640
+0.5V SENSOR BRIDGE AMPLIFIER
Equation 2
Voltage Controlled Setpoint Using RTD Sensors
VIN = 0.5 -
RRTD 2R2
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WHY5640
PAGE 11
OPERATION
Example 2
Using a 100 RTD with External Voltage Control
100 RTD R RTD 200
Example 2 demonstrates how to use an external voltage setpoint to control a 100 RTD from a range of 0 to 200 . Figure 10 illustrates the setpoint voltage, VIN, versus RTD resistance, RRTD, for Example 2.
+ VIN 1
1/2LM358
7 AGND AGND SENS
6 ERR
WHY5640
8. OPERATING WITH AD590 AND LM335 SENSORS
Figure 11 illustrates how to connect the WHY5640 for operation with PTC (Postive Temperature Coefficient) linear sensors AD590 and LM335. Equation 3 illustrates how to determine the setpoint resistance, RS, given a desired operating temperature measured in Celsius. Resistor, R3, is a fixed resistance value that can be used to scale or adjust the setpoint resistor, RS. Select resistor R3 equal to 10 k for most applications.
+0.5V SENSOR BRIDGE AMPLIFIER
Figure 10
Example 2 Setpoint Voltage vs. RTD Resistance
0.5 Setpoint Voltage (Volts) 0.4 0.3 0.2 0.1 0 0.00 50 100 150 RTD Resistance (kohms) 200 100 RTD
Figure 11
AD590 and LM335 Operation
VDD 1 k
1 A/Kelvin
VDD AD590
10 mV/Kelvin 9 k LM335 +VT 1 k -VT 1 k
VT = 1 mV/Kelvin
SETPOINT RESISTOR R S
R
3
+VT -VT
1
1/2LM358
7 6
AGND
SENS
ERR
WHY5640
+0.5V SENSOR BRIDGE AMPLIFIER
Equation 3
AD590 and LM335 Setpoint Resistance Calculation
Rs = 2R3 [0.5-(273.15+TCELCIUS )(1mV / Kelvin)] (c) 2001, 2003 WHY5640-00400-A Rev B www.teamwavelength.com
WHY5640
OPERATION
Example 3
Using an AD590 Example
VDD
AD590 1/2 LM358 1.5 k
PAGE 12
SETPOINT RESISTOR 5 k TRIMPOT
RS 10 k
Example 3 demonstrates how to use an AD590 to control from -50 C to +150 C. Figure 12 illustrates the setpoint resistance, VIN, versus AD590 temperature, for Example 3.
1 A/Kelvin VT = 1 mV/Kelvin 1 k
1
7
6
AGND
SENS
ERR
WHY5640
9. MONITORING SETPOINT AND ACTUAL SENSOR VOLTAGES
Figure 13 illustrates how to configure the WHY5640 so the setpoint and actual sensor voltages can be monitored externally. The WHY5640 internal sensor bridge amplifier becomes balanced (or Pin 6 (ERR) equals 1 Volt) when the sensor voltage equals the setpoint voltage in Figure 13. The circuit shown in Figure 13 uses a constant current source to produce a sensing current through the resistive temperature sensors resulting in a sensor voltage. A typical sensing current for 20 k and lower thermistors is 100 A. For thermistors higher than 20 k use 10 A. RTD's require a sensing current of 1mA. PTC (Positive Temperature Coefficient) sensors such as RTD sensors, the AD590, and the LM335 require that the output Pins 9 (OUTA) and 14 (OUTB) be swapped to produce the proper cooling and heating currents through the thermoelectric.
+0.5 V SENSOR BRIDGE AMPLIFIER
Figure 12
Example 3 Setpoint Resistance vs AD590 Temperature
6 Setpoint Resistance (kohms) 5 4 3 2 1 0 -50 0 50 100 150 Temperature (Celcius) RS Setpoint Resistor
Figure 13
Monitor Setpoint and Actual Sensor Voltages
VDD R4 ISENSE= VREF1 R4
VREF1
2N3906
LM324A
RT or RRTD THERMISTOR OR RTD SENSOR VOLTAGE MONITOR 10 k LM324D
VDD
10 k RG RL
LM324B
CL
VREF2
10 k LM324C SETPOINT VOLTAGE MONITOR 10 k
10 k
10 k
1
7
6
5
3
AGND
SENS
ERR
PI
LIMA
WHY5640
+0.5V SENSOR BRIDGE AMPLIFIER +1V PROPORTIONAL/INTEGRAL CONTROL LOOP
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OPERATION
PAGE 13
10. ADJUSTING THE CONTROL LOOP PROPORTIONAL GAIN
The control loop proportional gain can be adjusted by inserting a resistor, RR, between Pin 5 (P) and Pin 3 (LIMA) and a resistor, RG, between Pin 5 (PI) and Pin 6 (CRR). Equation 4 demonstrates how to calculate the Proportional gain, P, given a value for RP and RG. Table 2 lists the suggested resistor values for RL and RG versus sensor type and the thermal loads ability to change temperature rapidly.
Equation 4
Calculating P From RL and RG
Table 2
Proportional Gain Resistor RL and RG vs Sensor Type and Thermal Load Speed
RL 4 M 4 M 4 M 4 M 4 M RG 3.2 M 800 k 320 k 160 k 800 k Proportional Gain, [Amps/Volt] 5 20 50 100 20 Sensor Type/ Thermal Load Speed Thermistor/Fast Thermistor/Slow RTD/Fast RTD/Slow AD590 or LM335/ Fast AD590 or LM335/ Slow
11. ADJUSTING THE CONTROL LOOP INTEGRATOR TIME CONSTANT
The control loop integrator time constant can be adjusted by inserting a series of capacitors CL and a resistor, RL, between Pin 5 (PI) and Pin 3 (LIMA). Equation 5 demonstrates how to calculate the integrator time constant, ITC, given values for RL and CL. Table 3 lists the suggested resistor and capacitor values for RL and CL versus sensor type and the thermal loads ability to change temperature rapidly.
4 M
320 k
50
Equation 5
Calculating I From RR and CL
Table 3
Integrator Time Constant vs Sensor Type and Thermal Load Speed
RL 4 M 4 M 4 M 4 M 4 M CL 7 F 10 F 1 F 3 F 3 F Integrator Time 7 Constant 7 10 1 3 3 Sensor Type/ Thermal Load Speed Thermistor/Fast Thermistor/Slow RTD/Fast RTD/Slow AD590 or LM335/ Fast AD590 or LM335/ Slow
4 M
10 F
10
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OPERATION
PAGE 14
12. CHOOSING RG, RL, AND CL
The WHY5640 maintains a constant load temperature using a PI (Proportional Gain, Integrator) control loop. The operation of the PI control loop is dependent on the selection of RG, RL, and CL. Optimum values of RG, RL, and CL can be determined by applying a constant current to the thermoelectric and measuring its thermal load response versus time. Figure 14 illustrates a typical thermal load response to a constant current (power) being applied to the thermoelectric. Notice that the sensor voltage (temperature) does not immediately change when a current is applied to the thermoelectric. This delay is referred to as thermal lag, L, and dependent on the mass of the load and the amount of power being delivered to the thermoelectric. Eventually the changing sensor voltage begins to approach the final stable sensor voltage exponentially. The time it takes for the sensor voltage to reach 63% of the final temperature difference is referred to as the thermal time constant, . Small thermal loads powered by large thermoelectrics exhibit small thermal time constants. Large thermal loads powered by small thermoelectrics exhibit large thermal time constants. The final sensor voltage difference, VD, is the result of the end sensor voltage, VTEND, minus the beginning sensor, VTBEGIN.
Figure 15 shows how to configure the WHY5640 to measure the thermal load response parameters, L, , and VD. Steps to configuring the WHY5640 to find L, , and VD a) Adjust the setpoint resistor, RS, to the desired thermistor resistance that the load will eventually be stabilized at. b) Select values for RA or RB so that the maximum output current is limited to approximately 1/4th the thermoelectric's maximum rating. The maximum output current will be referred to as the thermoelectric step current, ITESTEP. Adjusting these values may require some experimentation. Be sure to not overheat or under cool the device you are trying to temperature control. Excessive heating (cooling) or fast changes in temperature can damage some devices. c) Disable the output current using the Enable/ Disable Switch 1 before applying power to the WHY5640. d) If you are controlling temperature above the ambient temperature then select heating current using the Heat/Cool Switch 2. Select cooling current with Switch 2 when controlling temperature below ambient. e) Connect a digital oscilloscope or a multimeter connected to a data acquisition system between Pins 6 (ERR) and 1 (AGND). f) Apply power to the WHY5640. Enable the output current using the Enable/Disable Switch 1 and immediately begin measuring the error voltage versus time. Once the error voltage flattens or changes little over time then stop taking measurements and analyze the thermal response, measuring L, , and VD. Equation 6 calculates VD which is the difference between the beginning error voltage on Pin 6 (ERR) and the ending error voltage on Pin 6 (ERR).
Figure 14
Thermal Load Time Response
Equation 6
Calculating VD
VD = (VTEND - VTBEGIN)
Equation 7 calculates RL given and CL. Begin by assuming a value of 1 F for CL. If RL begins to exceed 10 M then increase CL and recalculate RL.
Equation 7
Calculating RL
(c) 2001, 2003 WHY5640-00400-A Rev B
RL =
1.2 CL
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PAGE 15
OPERATION
Equation 8 calculates RG given L, CL, VD, and ITESTEP.
Figure 15
Configuring the WHY5640 to measure L, , VD
Equation 8
Calculating RG
RG = 13.7
(
L CL
) (I V )
D TESTEP
Easy Method for Measuring L and Measuring L and can sometimes be very difficult without the right equipment. The following steps can be used to quickly determine L and . a) Perform the same steps described above to find L, , and VD. b) Simply measure the time t90% it takes VD to reach approximately 90% of its final value. This is an approximation. This occurs when the error voltage begins to flatten significantly. The thermal time constant can be approximated as: =
(t90%) 4
The thermal lag can then be approximated from the thermal time constant, t, as:
L=
t90%
20
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PAGE 16
OPERATION
Example 4
Solving for RG, RL, and CL when controlling a laser diode thermal load. Figure 16 shows the WHY5640 configured to measure L, , and VD for a hermetically sealed laser diode load using a 1.6 Amp thermoelectric and a 10 k thermistor to sense temperature. For this example, the desired thermistor resistance the laser diode will be operated at is 12 k . Therefore, the setpoint resistor will be set to:
Figure 16
Configuring the WHY5640 to measure L, and VD for a Laser Diode Thermal Load Using a 1.6 AMP Thermoelectric and a 10 K Thermistor.
10 k
THERMISTOR THERMOELECTRIC
RT
VS
+ VDD
+
HEAT
COOL
NC
RS = 12 k Since the setpoint resistance is greater than 12 k , the laser diode will be cooled. Using the approximation in step (b), the maximum output current will be limited to (1.6 Amps/4) or 400 mA. Table 1 indicates that resistor RA should be 1.83 k to limit the output cooling current at 400 mA. Resistor RA is already in series with a 1.5 k resistor so RA should be selected as: RA = 1.83 k - 1.5 k = 330 Assume the thermistor resistance begins at 10 k and ends at 14 k some time after the 400 mA thermoelectric current is applied. Voltage difference, VD will then be: VD = (1.083 V - 0.917 V) = 0.167 V For this laser diode thermal load we find: L = 1 second and = 5 seconds Assume: CL = 1 F Then: RL = 1.2 = (1.2)(5 sec) = 6M 1F CL L ( C )( I
L
RS 12 k
SWITCH 2
8
9
10 11 12 13 14
WHY5640 TEC CONTROLLER 7 6 5 4
NC
3
2
1
10 k +VERR 1 M -VERR
Measure VERR to find: L , , and VD
1.5 k
SETPOINT TRIMPOT
1.5 k ENABLE SWITCH 1
RA 330
RB 330
DISABLE
RG = 13.7
(c) 2001, 2003
VD
TESTEP
1 0.167V ) = 13.7 (1F)( 400mA ) = 5.7M or R 6M
WHY5640-00400-A Rev B www.teamwavelength.com
WHY5640
PAGE 17
OPERATION
13. INCREASING OUTPUT CURRENT DRIVE
The WHY5640 is specifically designed to operate in a master/slave output current boosting configuration. Two or more WHY5640 controllers can be coupled to boost the output current. Figure 17 shows how to connect two WHY5640 controllers together to increase the output current drive to 4 Amps. Pin 4 (BUFA) and Pin 14 (BUFB) provide buffered outputs of Pin 3 (LIMA) and Pin 2 (LIMB), respectively. The slave controller is controlled by the master controller by connecting Pin 4 (BUFA) of the master unit to Pin 3 (LIMA) of the slave unit. Similarly, Pin 14 (BUFB) of the master unit then connects to Pin 2 (LIMB) of the slave unit. Each successive slave unit uses its buffered outputs, Pins 4 and 14, to drive then next slave units output drive section via its Pins 3 and 2. The master controller sets the current limits for all successive slave controllers connected to the master controller, requiring only one set of heat and cool limit resistors. Use Table 5 to determine the limit setting resistors, RA and RB , based on the number of WHY5640 controllers paralleled together.
Table 4
Current Limit Set Resistor vs Maximum Output Current vs Number of Paralleled WHY5640 Controllers.
Maximum Output Current (Amps)
1 WHY5640 Controller 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2 WHY5640 Controllers 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 3 WHY5640 Controllers 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4 5.7 6 6.3 6.6 6.9 4 WHY5640 Controllers 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6 6 6.4 6.8 7.2 7.6 8 8.4 8.8 9.2 5 WHY5640 Controllers 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11 11.5
Current Limit Set Resistor (k) 1.60 1.69 1.78 1.87 1.97 2.08 2.19 2.31 2.44 2.58 2.72 2.88 3.05 3.23 3.43 3.65 3.88 4.13 3.95 4.42 4.72 5.07 5.45 5.88
(c) 2001, 2003
WHY5640-00400-A Rev B
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WHY5640
PAGE 18
OPERATION
Figure 17
Boosting Output Current Drive
(c) 2001, 2003
WHY5640-00400-A Rev B
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WHY5640
OPERATION
PAGE 19
15. HELPFUL HINTS
Selecting a Temperature Sensor Select a temperature sensor that is responsive around the desired operating temperature. The temperature sensor should produce a large sensor output for small changes in temperature. Sensor selection should maximize the voltage change per C for best stability. Table 6 compares temperature sensors versus their ability to maintain stable load temperatures with the WHY5640. Mounting the Temperature Sensor The temperature sensor should be in good thermal contact with the device being temperature controlled. This requires that the temperature sensor be mounted using thermal epoxy or some form of mechanical mounting and thermal grease. Hint: Resistive temperature sensors and LM335 type temperature sensors should connect their negative termination directly to Pin 13 (GND) to avoid parasitic resistances and voltages effecting temperature stability and accuracy. Avoid placing the temperature sensor physically far from the thermoelectric. This is typically the cause for long thermal lag and creates a sluggish thermal response that produces considerable temperature overshoot once at the desired operating temperature. Mounting the Thermoelectric The thermoelectric should be in good thermal contact with its heatsink and load. Contact your thermoelectric manufacturer for their recommended mounting methods. Heatsink Notes If your device stabilizes at temperature but then drifts away from the setpoint temperature towards ambient, you are experiencing a condition known as thermal runaway. This is caused by insufficient heat removal from the thermoelectric's hot plate and is most commonly caused by an undersized thermoelectric heatsink. Ambient temperature disturbances can pass through the heatsink and thermoelectric and affect the device temperature stability. Choosing a heatsink with a larger mass will improve temperature stability.
(c) 2001, 2003 WHY5640-00400-A Rev B www.teamwavelength.com
Table 5
Temperature Sensor Comparison
SENSOR RATING Thermistor Best RTD Poor AD590 Good LM335 Good
WHY5640
PAGE 20
MECHANICAL SPECIFICATIONS
TOP VIEW
SIDE VIEW
BOTTOM VIEW
PIN DIAMETER: PIN LENGTH: PIN MATERIAL: HEAT SPREADER: PLASTIC COVER: ISOLATION: THERMAL WASHER: HEATSINK: FANS: 0.028" 0.126" Nickel Plated Steel Nickel Plated Aluminum LCP Plastic 1200 VDC any pin to case WTW002 WHS302 WXC303 (+5VDC) or WXC304 (+12VDC)
(c) 2001, 2003
WHY5640-00400-A Rev B
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WHY5640
PAGE 21
MECHANICAL SPECIFICATIONS
PCB FOOTPRINT
TOP VIEW
WHY5640 ASSEMBLED WITH HEATSINK AND FAN ACCESSORIES
Screw: 4-40 PHPH (x.75" w/o FAN) (x1" w/ FAN)
Air Flow
WXC303 (+5VDC) or WXC304 (+12VDC) 30 mm FAN
WHS302 Heatsink
WTW002 Thermal Washer
WHY5640
(c) 2001, 2003
WHY5640-00400-A Rev B
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WHY5640
PAGE 22
MECHANICAL SPECIFICATIONS
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WHY5640
PAGE 23
CERTIFICATION AND WARRANTY
CERTIFICATION: Wavelength Electronics (WEI) certifies that this product met it's published specifications at the time of shipment. Wavelength further certifies that its calibration measurements are traceable to the United States National Institute of Standard and Technology, to the extent allowed by that organization's calibration facilities, and to the calibration facilities of other International Standards Organization members. WARRANTY: Wavelength, will, at it's option, either repair or replace products which prove to be defective. WARRANTY SERVICE: For warranty service or repair, this product must be returned to the factory. For products returned to Wavelength for warranty service, the Buyer shall prepay shipping charges to Wavelength and Wavelength shall pay shipping charges to return the product to the Buyer. However, the Buyer shall pay all shipping charges, duties, and taxes for products returned to Wavelength from another country. LIMITATIONS OF WARRANTY: The warranty shall not apply to defects resulting from improper use or misuse of the instrument outside published specifications. No other warranty is expressed or implied. Wavelength specifically disclaims the implied warranties of merchantiability and fitness for a particular purpose. EXCLUSIVE REMEDIES: The remedies provided herein are the Buyer's sole and exclusive remedies. Wavelength shall not be liable for any direct, indirect, special, incidental, or consequential damages, whether based on contract, tort, or any other legal theory. NOTICE: The information contained in this document is subject to change without notice. Wavelength will not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material. No part of this document may be photocopied, reproduced, or translated to another language without the prior written consent of Wavelength. SAFETY: There are no user serviceability parts inside this product. Return the product to Wavelength Electronics for service and repair to assure that safety features are maintained. LIFE SUPPORT POLICY: As a general policy, Wavelength Electronics, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the Wavelength Electronics, Inc. product can be reasonably expected to cause failure of the life support device or to significantly affect its safety or effectiveness. Wavelength Electronics, Inc. will not knowingly sell its products for use in such applications unless it receives written assurances satisfactory to Wavelength Electronics, Inc. that the risks of injury or damage have been minimized, the customer assumes all such risks, and there is no product liability for Wavelength Electronics, Inc. Examples or devices considered to be life support devices are neonatal oxygen analyzers, nerve stimulators (for any use), auto transfusion devices, blood pumps, defibrillators, arrhythmia detectors and alarms, pacemakers, hemodialysis systems, peritoneal dialysis systems, ventilators of all types, and infusion pumps as well as other devices designated as "critical" by the FDA. The above are representative examples only and are not intended to be conclusive or exclusive of any other life support device.
(c) 2001, 2003
WHY5640-00400-A Rev B
www.teamwavelength.com
WHY5640
PAGE 24
WAVELENGTH ELECTRONICS, INC. 51 Evergreen Drive Bozeman, Montana, 59715 phone :(406) 587-4910 Sales and Technical Support :(406) 587-4183 Accounting fax :(406) 587-4911 e-mail :sales@teamwavelength.com web :w w w. w av e l e n g th e l e c tro n i c s . c o m
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www.teamwavelength.com

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