Key Featuresa
Item #	MTD415L(E)	MTD415T(E)	MTD1020T
Supported Temperature Sensor	LMT84 IC	10 kΩ Thermistor
Output Current (See Graphs on Specs Tab)	Up to ±1.5 A		Up to ±2.0 A
TEC Compliance Voltage	4.0 V		10.0 V
Maximum Output Power (See Graphs on Specs Tab)	Up to 6.0 W		Up to 20.0 W
Noise and Ripple (Typical)	150 mA (Peak-Peak) or 87 mA RMS
Temperature Stability (Typical)	100 mK
Data Sheet (Click for PDF)

• See the Specs and Pin Diagram tabs above for additional information.

Volume Pricing & OEM Support

Thorlabs' production facilities are capable of manufacturing TEC controllers in high volumes, and we pass the savings associated with planned production on to our customers.

Contact our OEM team to learn more. An OEM specialist will contact you within 24 hours or on the next business day.

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Upon request, large-quantities of MTD415 series drivers in SMT packages can be delivered in an IC tube.

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Application Example
MTD415L TEC drivers are used for temperature regulation in Thorlabs' Nanosecond Pulsed Laser Systems, as shown in this cutaway view of the NPL64A.

Features

• Integrated Drivers with Digital PID Loops for TECs
• Three Packages Available: THT, SMT, and SMT on Daughterboard
• Low Output Current Noise: ≤150 mA
• Units can be Controlled via a PC
  • Accepts Serial Commands over UART Entered through a Command Line Interface
  • GUI to Adjust Settings and Monitor Driver Performance (See Software Tab)
• Evaluation Board Available for Testing and Evaluating Driver Settings

Applications

• Ideal for Small Assemblies that Use Thermoelectric Coolers
• Active Cooling and Temperature Stabilization for
  • Laser Modules and Laser Diodes
  • WDM and DWDM Laser Diodes
  • EDFA Optical Amplifiers
  • Photodetectors and Photodiodes
  • Automated Test Equipment (ATE)

Thorlabs offers several complete driver module options designed for OEM system integration. The high compliance voltage of the MTD1020T, which is offered in a through-hole technology (THT) package, allows it to deliver the maximum ±2.0 A TEC current into load resistances up to 5 Ω. The MTD415 Series, which are offered in surface-mount technology (SMT) packages and as SMT packages mounted on daughterboards, deliver TEC current up to ±1.5 A depending on the load resistance. Please see the Specs tab for typical performance plots and specifications.

Each of these OEM-grade TEC drivers employs a digital control loop to regulate the current output. These PID control loops enable our TEC drivers to provide faster temperature settling times and better stability than drivers using PI control loops. True bipolar operation allows the output current to reach 0 A without "dead zones" or other nonlinearities at low TEC currents. The complete on-chip power stage and thermal control loop circuitry minimize external components while maintaining high efficiency and low output current noise of ≤150 mA. The output current is directly controlled to eliminate current surges to the TEC, while an adjustable TEC current limit provides protection against overdriving the cooler.

Computer Control
These drivers use a UART digital control interface that allows quick access to PID settings, all other system parameters, and digital measurement data, enabling easy integration into a variety of systems. The TEC drivers are controlled via a PC using either the programming commands outlined in the TEC driver data sheets (linked to in the table above) or a GUI for Windows^® operating systems (see the Software tab). This GUI provides a simple means of optimizing the TEC driver settings to a specific thermal load, as well as graphical output that tracks the TEC performance. See the PID Oscillation Test tab for an example of how to set the PID parameters using the GUI.

Evaluation Board
For those customers interested in evaluating the performance of the MTD series TEC drivers and optimizing their response to a particular thermal load, we offer the MTDEVAL1 evaluation board. The evaluation board has a built-in UART-to-USB adapter that allows commands sent from a PC to address the mounted driver.

All technical data are valid at 23 ± 5 °C and 45 ± 15% relative humidity (non-condensing).

MTD415 Series Typical Output Characteristics

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MTD415 Series deliver the maximum output power of 6 W into a load resistance of 2.66 Ω when operating under recommended conditions. The shaded range corresponds to load resistances less than 2.66 Ω, for which the maximum output power depends on environmental conditions.

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MTD415 Series deliver the maximum TEC current of 1.5 A into a load resistance of 2.66 Ω when operating under recommended conditions. The maximum output current drops for higher load resistances due to the limit of the compliance voltage. The shaded range corresponds to load resistances less than 2.66 Ω, for which the maximum output current depends on environmental conditions.

MTD1020T Typical Output Characteristics

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MTD1020T delivers the maximum output power of 20 W into a load resistance of 5 Ω, when operating under recommended conditions and actively cooled, or for ambient temperatures between -20 °C and 20 °C when convection cooled. The red curve applies to an ambient temperature of 60 °C and convection cooling.

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MTD1020T delivers the maximum TEC current of 2.0 A into load resistances up to 5 Ω, when operating under recommended conditions and actively cooled with 2 m/s forced air or cooling methods at least equally effective. When convection cooled, the maximum 2.0 A current can be delivered into any load resistances up to 5 Ω for ambient temperatures up to 20 °C. Other cooling methods may give intermediate results.

Click on the following links to move to the different sections in this discussion.

• Pin Layout of the MTD415 Series
• Typical Application Circuits for the MTD415 Series
• Pin Layout of the MTD1020T
• Typical Application Circuit for the MTD1020T

Pin Layout of the MTD415 Series

Typical Application Circuits for the MTD415 Series

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Sample External Circuit for MTD415L TEC Driver

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Sample External Circuit for MTD415T TEC Driver

Pin Layout of the MTD1020T

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Sample External Circuit for MTD1020T TEC Driver

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The OEM Temperature Controller GUI Interface

GUI and Drivers for OEM Temperature Controllers and Evaluation Board

The download button below provides a link to the GUI and drivers that allow these TEC drivers to be controlled via a PC with a Windows^® operating system. The software can be used to perform an oscillation test and can automatically calculate the optimal P, I, and D parameters for a setup using the results. For details on the oscillation test procedure and an introduction to PID circuits, see the PID Oscillation Test tab.

Software

Version 1.5 (April 21, 2021) 
This is a software package with a GUI and drivers for Thorlabs' OEM TEC drivers in SMT packages.

Oscillation Test Starting Parameters
Set Temperature	25.000 °C
P Share	1000 mA/K
I Share	0 A/Ks
D Share	0 As/K
Cycle Time	30 ms

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Figure 2: Initial Settling Behavior after TEC is Enabled

Figure 1: Starting Parameters for the Oscillation Test

Oscillation Test to Set PID Parameters

Each MTD415 and MTD1020T module incorporates a digital PID controller. The P, I, and D shares can be programmed manually or calculated automatically by the firmware by entering the results of a loop oscillation test. This test can be performed using the GUI available on the Software tab, and provides a convenient method for optimizing the PID parameters.

Before running the test, the following preconditions must be met:

• TEC Current Limit is Set to 1 A
• All Connections are Made Properly
• Temperature Window Settings in the GUI's Software Settings
  
  • Set the Temperature Window to ±100 mK
  • Display only the Actual Temperature
  • Set the X-Axis of the Temperature Graph to a Max Time of 60 s

First, enter the PID loop settings shown in the table to the upper right. These initial settings allow the user to observe the temperature settling process, as typically no oscillations will appear when the driver is operated with these settings. Then, enable the TEC. The actual temperature, measured by the unit and recorded on the graph in the GUI, will approximate the set value.  

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Figure 4: P Share = 5000 mA/K

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Figure 3: P Share = 10,000 mA/K

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Figure 6: P Share = 2000 mA/K

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Figure 5: P Share = 3000 mA/K

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Figure 8: P Share = 2800 mA/K

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Figure 7: P Share = 2600 mA/K

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Figure 10: P Share = 2650 mA/K

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Figure 9: P Share = 2700 mA/K

The critical P share (critical gain) is the value at which the system starts to oscillate for a minimum of 20 cycles without a drop in amplitude as a reaction to a change in the temperature setpoint. The procedure for the oscillation loop test used to find the critical P share is described as follows: with I and D set at zero, the P share value is set high enough that the loop oscillates without damping. Then, smaller P share values are tested until the oscillations are damped. The P share is increased again by a smaller amount until the loop begins to oscillate continuously again, and then decreased to find the threshold where the oscillations become damped again. After each change in the P share value, the temperature setpoint must be changed slightly to trigger the loop with the new P share setting. The process is repeated until the minimum P share value for the loop to oscillate without damping is found; this is the critical P share value.

The following example illustrates how the oscillation loop test procedure is carried out. For this case, a passive thermal load consisting of a 60 mm x 60 mm x 25 mm radiator was connected to a TEC and a temperature sensor.

1. After entering the initial settings and enabling the TEC (Figure 1), the temperature begins to settle (Figure 2).
2. The P share is set to 10,000 mA/K, since this value is high enough that it will trigger the loop to oscillate for almost any thermal load. Then, the set temperature is increased by 0.1 K to 25.1 °C. The loop begins to show strong oscillations (Figure 3).
3. The P share is lowered to 5000 mA/K and the set temperature is decreased to 25.0 °C again. The loop continues to oscillate (Figure 4).
4. The P share is lowered again to 3000 mA/K and the set temperature increased to 25.1 °C. The loop continues to oscillate (Figure 5). 
5. The P share is lowered to 2000 mA/K and the set temperature is decreased to 25.0 °C. The oscillations are now damped (Figure 6).
6. The P share is increased to 2600 mA/K and the set temperature to 25.1 °C. The oscillations are still damped (Figure 7).
7. The P share is increased again to 2800 mA/K and the set temperature decreased to 25.0 °C. The loop begins to oscillate again (Figure 8).
8. The P share is lowered to 2700 mA/K and the set temperature increased to 25.1 °C. The loop continues to oscillate (Figure 9).
9. The P share is lowered to 2650 mA/K and the set temperature decreased to 25.0 °C. The loop still oscillates (Figure 10).
10. At this point, we know that at 2600 mA/K, the oscillations were damped (step 6), so 2650 mA/K is the lowest P share value for which the loop will oscillate continuously. This value will be used for the critical gain.
11. Use the diagram from step 9 (Figure 10) to calculate the critical period (i.e., the time of one oscillation). Count the number of oscillations across the 60 s observation window and divide 60 by this number. In this case, there are 11.8 periods, so each period has a duration of approximately 5.085 s.
12. Enter the critical gain (step 10) and critical period duration (step 11) into the GUI (Figure 11). Press enter to trigger the calculation of the PID shared and cycle time by the firmware. The calculated loop parameters will be displayed immediately (Figure 12).

Typically, the PID optimization for settling behavior is finished at this point. If required, the PID values and the cycle time can be manually fine-tuned in order to optimize the loop response to changes of the thermal load.

Saving the PID Parameters for Later Use
These TEC drivers are designed with a temporary volatile memory and a non-volatile flash memory. As the flash memory has a limited number of erase-write cycles, parameters entered into the GUI will be saved in the volatile memory only, unless otherwise directed by the user. This means that these parameters will be immediately applied to the driver operation, but will not be saved when the unit is powered down. All parameters can be saved to both the non-volatile flash memory and volatile memory by pressing the Save Settings in MTD Flash button in the GUI; parameters saved to the non-volatile memory will be applied the next time that the unit is powered on.

Figure 12: Final Calculated PID Parameters

Figure 11: Entering the Critical Gain and Critical Period Duration

Alternatively, the PID parameters can be saved to the computer running the GUI. The next time that the GUI is used to operate the TEC driver, the saved parameters can be loaded into the GUI and will automatically populate all of the fields; the user can then select whether to save these parameters to the volatile memory only (meaning that the driver will immediately use the parameters), or to save the parameters to both the volatile and non-volatile memory.

Notes
The cycling time is the time basis of the internal digital control loop and is calculated automatically by entering the critical gain and the critical oscillation period. If the cycling time is manually reset, the firmware recalculates the I and the D shares.

The optimized PID parameters are valid for a steady state that is dependent on the set temperature as well as on the ambient conditions (ambient temperature, temperature of the thermally controlled object). Any changes in the operating and/or environmental conditions may require a re-adjustment of the PID parameters.

For more information on the basics of PID circuits, see the PID Tutorial tab.