IC Temperature Controllers in SMT or THT Packages

Overview
Specs
Pin Diagrams
Software
PID Oscillation Test
PID Tutorial
Feedback

Key Features^a
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)	<10 mA (TEC Element with 4 Ω Resistance)
Temperature Stability (Over 8 Hours, Typical)	Better than 20 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
Very Low Output Current Noise: <10 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 <10 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).

TEC Driver Specifications

Item #	MTD415L(E)	MTD415T(E)	MTD1020T
TEC Current Output
Maximum Output Current	Up to ±1.5 A (See Graphs Below)		Up to ±2.0 A (See Graphs Below)
TEC Compliance Voltage	4.0 V		10.0 V
Maximum Output Power	Up to 6.0 W		Up to 20.0 W
Measurement Resolution	3 mA (Typical) 8 mA (Max)		5 mA (Typical) 10 mA (Max)
Measurement Accuracy	±50 mA
Noise and Ripple (Typical)^a	<10 mA
TEC Current Limit
Setting Range^b	0 to 1.5 A		0 to 2.0 A
Setting Resolution	1 mA
Setting Accuracy	±50 mA
Temperature Sensor
Supported Sensor	LMT84 IC Sensor or Similar	10 kΩ Thermistor^c
Maximum Temperature Control Range^d	+5 °C to +45 °C
Temperature Setting Resolution	1 mK
Temperature Measurement Resolution^e	2 mK (Typical) 10 mK (Max)		3 mK (Typical) 10 mK (Max)
Absolute Temperature Accuracy^d	±0.5 °C
Temperature Stability over 8 Hours (Typical)	Better than 20 mK
Temperature Coefficient	<20 mK/°C
Recommended Operating Conditions
Supply Input Voltage	4.5 V to 5.5 V		11.5 V to 12.5 V^f
Ambient Temperature Range	-20 °C to 60 °C
Warm-Up Time for Rated Accuracy	10 Minutes
Programming Interface
Type	UART
Voltage Level	3.3 V Logic Level; Input 5 V Tolerant
Data Rate	115,200 bps; 8 Data Bits, 1 Stop Bit
Safety Features
Safety Features	TEC Current Limit Sensor Fault Protection TEC Open Circuit Protection Temperature Setpoint Limit Temperature Window Protection Delay Over Temperature Protection
Environmental
Storage Temperature	-40 °C to 100 °C

Measured with a TEC element with an equivalent resistance of 4 Ω.
Limits current magnitude.
Thermistor resistance given at 25 °C. Thermistor resistance measurement range should be 4.2 to 29 kΩ.
Control range and thermal stability depend on IC or thermistor temperature sensor parameters.
Maximum measurement resolution depends on cycle time settings.
At 10.0 V TEC Compliance Voltage

TEC Driver Absolute Maximum Ratings

The following TEC Driver Absolute Maximum Ratings specifications are given for the free-air operating temperature range unless otherwise noted. Operating these drivers outside of the maximum rated conditions listed in this table may affect product reliability and/or cause permanent damage to the product. These are stress ratings only; functional operation at these or any other conditions beyond the specifications listed in the TEC Driver Specifications table is not implied.

Item #		MTD415L(E)	MTD1020T
Supply Input Voltage		4.5 V to 6 V	11.5 V to 13.0 V
Supply Input Current		1.6 A	2.3 A
TEC Output Current		-1.5 A to +1.5 A	-2.0 A to +2.0 A
TEC Compliance Voltage		4.0 V	10.0 V
Maximum Output Power		6.0 W	20.0 W
Power Dissipation		1.5 W	4.0 W
Pin Voltage Range^b (With Respect to Ground Terminal)	VDD	-0.3 V to +6 V	-0.3 V to +13.0 V
	TX	-	-0.3 V to +3.6 V
	ENABLE, RX	-0.3 V to (VDD + 0.3 V)	-0.3 V to +3.6 V
	TEC-, TEC+	-0.3 V to (VDD + 0.3 V)	0.0 V to +13.0 V
	TEMP	-0.3 V to +3.3 V
Maximum Output Current (STATUS, TX)		10 mA
Maximum Input Current (ENABLE, RX)		10 mA
Ambient Operating Temperatures		-40 °C to 70 °C

At 10.0 V TEC Compliance Voltage
See the Pin Diagrams tab for pin assignments.

TEC Controller Package Dimensions

Item #	Package Type	Dimensions	Approximate Weight
MTD415L	SMT^a	21.0 mm x 12.4 mm x 3.1 mm (0.83" x 0.49" 0.12")	2 g
MTD415LE	Daughterboard	39.6 mm x 21.5 mm x 14.1 mm (1.56" x 0.85" x 0.55" )	4 g
MTD415T	SMT^a	21.0 mm x 12.4 mm x 3.1 mm (0.83" x 0.49" 0.12")	2 g
MTD415TE	Daughterboard	39.6 mm x 21.5 mm x 14.1 mm (1.56" x 0.85" x 0.55" )	4 g
MTD1020T	THT^b	27.0 mm x 21.0 mm x 10.3 mm^c (1.06" x 0.83" x 0.41")	8 g

Surface-Mount Technology
Through-Hole Technology
Height Dimension does not Include Pins

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.

MTDEVAL1 Evaluation Board

Specifications
Supply Input Voltage	11.5 VDC to 13.0 VDC
Supply Input Current (Maximum)	2.3 A
USB Connection	USB Mini B
Operating Temperature Range	0 °C to 40 °C
Storage Temperature Range	-40 °C to 70 °C
Dimensions	114.5 mm x 64.0 mm x 16.8 mm (4.51" x 2.52" x 0.66")
Weight	40 g

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

MTD415 Pin Layout
These pin assignments correspond to viewing the driver from the top when the engraving on the driver is right-side up.

Land Pattern Data of the MTD415L(E) and MTD415T(E)

MTD415L(E) TEC Driver
Pin	Name	Description
1	VDD	Supply Voltage Input (+4.5 V to +5.5 V)
2	GND	Supply Voltage Ground
3	GND	Supply Voltage Ground
4	DNC	Do Not Connect
5	DNC	Do Not Connect
6	VREF	Reference Output Voltage for LMT84 Temperature Sensor (1.8 V)
7	TEMP	LMT84 Temperature Sensor Input
8	GNDS	Temperature Sensor Ground This ground connection should be wired separately and not be shared with other Ground pins.
9	GND	Supply Voltage Ground
10	ENABLE	Enable Signal Input (Low-Active) Low = Enabled, High = Disabled Can be Connected Directly to GND
11	STATUS	Status Signal Output (Can be Left Floating) High = Temperature within Defined Temperature Window Low = Temperature outside Programmed Temperature Window or an Error Occurred
12	TX	Digital Interface Transmit Signal
13	RX	Digital Interface Receive Signal
14	GND	Supply Voltage Ground
15	TEC -	TEC Element Negative Connection
16	TEC +	TEC Element Positive Connection

MTD415T(E) TEC Driver
Pin	Name	Description
1	VDD	Supply Voltage Input (+4.5 V to +5.5 V)
2	GND	Supply Voltage Ground
3	GND	Supply Voltage Ground
4	DNC	Do Not Connect
5	DNC	Do Not Connect
6	VREF	Reference Output Voltage for Thermistor Temperature Sensor (1.8 V)
7	TEMP	Thermistor Temperature Sensor Input
8	GNDS	Temperature Sensor Ground Can be used for Shielding Purposes or Left Open
9	GND	Supply Voltage Ground
10	ENABLE	Enable Signal Input (Low-Active) Low = Enabled, High = Disabled Can be Connected Directly to GND
11	STATUS	Status Signal Output (Can be Left Floating) High = Temperature within Defined Temperature Window, Low = Temperature Outside Programmed Temperature Window or an Error Occurred
12	TX	Digital Interface Transmit Signal
13	RX	Digital Interface Receive Signal
14	GND	Supply Voltage Ground
15	TEC -	TEC Element Negative Connection
16	TEC +	TEC Element Positive Connection

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

MTD1020T Pin Layout
These pin assignments correspond to viewing the driver from the top when the engraving on the driver is right-side up.

Land Pattern
Top View of the MTD1020T

MTD1020T TEC Driver
Pin	Name	Description
1	VDD	Supply Voltage Input (+11.5 V to +12.5 V)
2	GND	Supply Voltage Ground
3	GND	Supply Voltage Ground
4	DNC	Do Not Connect
5	DNC	Do Not Connect
6	VREF	Reference Output Voltage for Thermistor Temperature Sensor (1.24 V)
7	TEMP	Thermistor Temperature Sensor Input
8	GNDS	Temperature Sensor Ground Can be used for Shielding Purposes or Left Open
9	GND	Supply Voltage Ground
10	ENABLE	Enable Signal Input (Low-Active) Low = Enabled, High = Disabled Can be Connected Directly to GND
11	STATUS	Status Signal Output (Can be Left Floating) High = Temperature within Defined Temperature Window, Low = Temperature Outside Programmed Temperature Window or an Error Occurred
12	TX	Digital Interface Transmit Signal
13	RX	Digital Interface Receive Signal
14	TEC -	TEC Element Negative Connection
15	TEC +	TEC Element Positive Connection
16	GND	Supply Voltage Ground

Typical Application Circuit for 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 1.4 (June 15, 2018)
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.

After entering the initial settings and enabling the TEC (Figure 1), the temperature begins to settle (Figure 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).
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).
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).
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).
The P share is increased to 2600 mA/K and the set temperature to 25.1 °C. The oscillations are still damped (Figure 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).
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).
The P share is lowered to 2650 mA/K and the set temperature decreased to 25.0 °C. The loop still oscillates (Figure 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.
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.
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.

PID Basics

The PID circuit is often utilized as a control loop feedback controller and is very commonly used for many forms of servo circuits. The letters making up the acronym PID correspond to Proportional (P), Integral (I), and Derivative (D), which represents the three control settings of a PID circuit. The purpose of any servo circuit is to hold the system at a predetermined value (set point) for long periods of time. The PID circuit actively controls the system so as to hold it at the set point by generating an error signal that is essentially the difference between the set point and the current value. The three controls relate to the time-dependent error signal; at its simplest, this can be thought of as follows: Proportional is dependent upon the present error, Integral is dependent upon the accumulation of past error, and Derivative is the prediction of future error. The results of each of the controls are then fed into a weighted sum, which then adjusts the output of the circuit, u(t). This output is fed into a control device, its value is fed back into the circuit, and the process is allowed to actively stabilize the circuit’s output to reach and hold at the set point value. The block diagram below illustrates very simply the action of a PID circuit. One or more of the controls can be utilized in any servo circuit depending on system demand and requirement (i.e., P, I, PI, PD, or PID).

Through proper setting of the controls in a PID circuit, relatively quick response with minimal overshoot (passing the set point value) and ringing (oscillation about the set point value) can be achieved. Let’s take as an example a temperature servo, such as that for temperature stabilization of a laser diode. The PID circuit will ultimately servo the current to a Thermo Electric Cooler (TEC) (often times through control of the gate voltage on an FET). Under this example, the current is referred to as the Manipulated Variable (MV). A thermistor is used to monitor the temperature of the laser diode, and the voltage over the thermistor is used as the Process Variable (PV). The Set Point (SP) voltage is set to correspond to the desired temperature. The error signal, e(t), is then just the difference between the SP and PV. A PID controller will generate the error signal and then change the MV to reach the desired result. If, for instance, e(t) states that the laser diode is too hot, the circuit will allow more current to flow through the TEC (proportional control). Since proportional control is proportional to e(t), it may not cool the laser diode quickly enough. In that event, the circuit will further increase the amount of current through the TEC (integral control) by looking at the previous errors and adjusting the output in order to reach the desired value. As the SP is reached [e(t) approaches zero], the circuit will decrease the current through the TEC in anticipation of reaching the SP (derivative control).

Please note that a PID circuit will not guarantee optimal control. Improper setting of the PID controls can cause the circuit to oscillate significantly and lead to instability in control. It is up to the user to properly adjust the PID gains to ensure proper performance.

PID Theory

The output of the PID control circuit, u(t), is given as

where
K_p= Proportional Gain
K_i = Integral Gain
K_d = Derivative Gain
e(t) = SP - PV(t)

From here we can define the control units through their mathematical definition and discuss each in a little more detail. Proportional control is proportional to the error signal; as such, it is a direct response to the error signal generated by the circuit:

Larger proportional gain results is larger changes in response to the error, and thus affects the speed at which the controller can respond to changes in the system. While a high proportional gain can cause a circuit to respond swiftly, too high a value can cause oscillations about the SP value. Too low a value and the circuit cannot efficiently respond to changes in the system.

Integral control goes a step further than proportional gain, as it is proportional to not just the magnitude of the error signal but also the duration of the error.

Integral control is highly effective at increasing the response time of a circuit along with eliminating the steady-state error associated with purely proportional control. In essence integral control sums over the previous error, which was not corrected, and then multiplies that error by K_i to produce the integral response. Thus, for even small sustained error, a large aggregated integral response can be realized. However, due to the fast response of integral control, high gain values can cause significant overshoot of the SP value and lead to oscillation and instability. Too low and the circuit will be significantly slower in responding to changes in the system.

Derivative control attempts to reduce the overshoot and ringing potential from proportional and integral control. It determines how quickly the circuit is changing over time (by looking at the derivative of the error signal) and multiplies it by K_d to produce the derivative response.

Unlike proportional and integral control, derivative control will slow the response of the circuit. In doing so, it is able to partially compensate for the overshoot as well as damp out any oscillations caused by integral and proportional control. High gain values cause the circuit to respond very slowly and can leave one susceptible to noise and high frequency oscillation (as the circuit becomes too slow to respond quickly). Too low and the circuit is prone to overshooting the SP value. However, in some cases overshooting the SP value by any significant amount must be avoided and thus a higher derivative gain (along with lower proportional gain) can be used. The chart below explains the effects of increasing the gain of any one of the parameters independently.

Parameter Increased	Rise Time	Overshoot	Settling Time	Steady-State Error	Stability
K_p	Decrease	Increase	Small Change	Decrease	Degrade
K_i	Decrease	Increase	Increase	Decrease Significantly	Degrade
K_d	Minor Decrease	Minor Decrease	Minor Decrease	No Effect	Improve (for small K_d)

Tuning

In general the gains of P, I, and D will need to be adjusted by the user in order to best servo the system. While there is not a static set of rules for what the values should be for any specific system, following the general procedures should help in tuning a circuit to match one’s system and environment. In general a PID circuit will typically overshoot the SP value slightly and then quickly damp out to reach the SP value.

Manual tuning of the gain settings is the simplest method for setting the PID controls. However, this procedure is done actively (the PID controller turned on and properly attached to the system) and requires some amount of experience to fully integrate. To tune your PID controller manually, first the integral and derivative gains are set to zero. Increase the proportional gain until you observe oscillation in the output. Your proportional gain should then be set to roughly half this value. After the proportional gain is set, increase the integral gain until any offset is corrected for on a time scale appropriate for your system. If you increase this gain too much, you will observe significant overshoot of the SP value and instability in the circuit. Once the integral gain is set, the derivative gain can then be increased. Derivative gain will reduce overshoot and damp the system quickly to the SP value. If you increase the derivative gain too much, you will see large overshoot (due to the circuit being too slow to respond). By playing with the gain settings, you can maximize the performance of your PID circuit, resulting in a circuit that quickly responds to changes in the system and effectively damps out oscillation about the SP value.

Control Type	K_p	K_i	K_d
P	0.50 K_u	-	-
PI	0.45 K_u	1.2 K_p/P_u	-
PID	0.60 K_u	2 K_p/P_u	K_pP_u/8

While manual tuning can be very effective at setting a PID circuit for your specific system, it does require some amount of experience and understanding of PID circuits and response. The Ziegler-Nichols method for PID tuning offers a bit more structured guide to setting PID values. Again, you’ll want to set the integral and derivative gain to zero. Increase the proportional gain until the circuit starts to oscillate. We will call this gain level K_u. The oscillation will have a period of P_u. Gains are for various control circuits are then given below in the chart.

Posted Comments:

Artem Gulyaev (posted 2020-12-23 12:02:02.997)

Hi, Just for a bit convenience for the end user, could you please add in your datasheet that MTD415L answers for every "set" command with either * corresponding value which was set * with error message surprisingly is was never declared in the datasheet, while is true. Also probably error resetting mask also would be of some use - usually users might want to reset minor errors (like invalid value set attempt) while keeping the important ones. So "c" command might be accompanied with a mask value to erase. Kind Regads, Artem Gulyaev

MKiess (posted 2021-01-21 08:41:25.0)

Thank you very much for this feedback. We will take a closer look at this topic again and see how we can make this more accessible to the end user, as described by you. Thank you very much for this suggestion. Such comments help us to constantly improve our products.

Ludovic Angot (posted 2020-07-23 07:43:40.233)

I am currently writing my own code to use the MTDEVAL1 on a single board computer, the first step being a loopback test. To do so, can I safely only connect the USB cable and put a jumper on pins 12 and 13 (corresponding e.g. to TX and RX on the MTD1020) of either one of the carrier socket of the MTDEVAL1? Or does the evaluation board need to be powered via the Screw terminal 1 in order for the USB to UART to function?

dpossin (posted 2020-07-24 08:09:19.0)

Dear Ludovic, Yes, with no MTD module inserted you can use a jumper between pins 12 and 13 for the loopback test. You don’t need to add an external power supply.

user (posted 2020-07-01 18:13:53.153)

How many number of times can we program to the flash memory on MTD415T? Thank you.

MKiess (posted 2020-07-06 07:56:37.0)

This is a response from Michael at Thorlabs. Thank you very much for your feedback. Depending on the application, more than 100k erase / write cycles are possible for the non-volatile memory (flash). We have the possibility to adapt the settings for your specific application to maximize the lifetime of the controller. I have contacted you directly to discuss this with you in more detail.

user (posted 2020-04-20 18:09:33.047)

This is a nice product, I think two changes/variations would make it great. 1) A higher temperature version. Many devices, such as doubling crystals, need to run at higher temps. I imagine you don't allow higher than +45 C because you cannot guarentee the ~ mK accuracy. For many applications ~ mK is not required. (For those out there who need a higher temp add a resistor to one of the sensor wires. The temp reading will no longer be accurate, and thorlabs specs won't hold at the higher real temp, but it works fine.) 2) compact version. Although this is an eval board it would be quite useful if the footprint was reduced. It seems like it could be cut in half easily, maybe even by more with some effort.

wskopalik (posted 2020-04-21 11:57:11.0)

This is a response from Wolfgang at Thorlabs. Thank you very much for your feedback! We appreciate any feedback that helps us to improve our products. I will forward your suggestions to our engineering team so we can consider them for future releases in this product line.

user (posted 2019-10-23 08:32:31.37)

The screw terminals for TEC+ and TEC- are too large to make proper contact with AWG 22 / 0.3 mm2 wires. The wire will be held in place barely, but will not have proper contact and can be pulled out by a little bit of force. Be sure to use suitable wires with larger cross sectional area to ensure proper contact. The screw terminals for the power supply and sensor connection are both OK and don't have this issue.

MKiess (posted 2019-10-29 11:49:46.0)

This is a response from Michael at Thorlabs. Thank you very much for your feedback. We appreciate any feedback that helps us to improve our products and helps all users to use them.

user (posted 2019-09-10 11:47:03.03)

I'm controlling the PTC1 with my own SW via serial port according to the programmers reference of the MTD1020T, but I have encountered some communication problem. The documentation is wrong, the Command/Response terminator is CR and not LF and each response value is followed by char '>' (62/0x3E).

MKiess (posted 2019-09-20 03:58:05.0)

This is a response from Michael at Thorlabs. Thank you for the feedback. We will take a look at this and correct the documentation. Thank you very much for this information.

Ludovic Angot (posted 2019-07-29 22:40:27.34)

I am planning to use the MTDEVAL1 on a linux system. I have already taken note of the programmer's reference of the TEC modules but there's nothing about UART control in the MTDEVAL1 manual. Could you please provide any guidelines to get me (and probably others) started on this? It may be as simple as connecting the eval. board, detecting the USB port and then send the appropriate commands, but I prefer to know beforehand to avoid any mistake. A short section on the topic could be added to the user manual. Also in paragraph 3 Operating Principle of the MTDEVAL1 manual, reference is made to saving the parameters to an XML file, could you provide an example of such an file?

dpossin (posted 2019-08-28 04:45:02.0)

Dear Hinoki, Thank you for your Feedback. The MTD Series uses standard serial communication over a virtual COM port for data transfer. To control one of our MTD modules with a Linux based system you just need to use the operating system proprietary serial communication interface and you can use the standard commands mentioned in the manual. I hope that helps.

user (posted 2019-07-09 17:16:26.473)

Hi, is there a way to change the y-axis range in the MTD software? If my set temperature is 25 C, can I set the temperature range in the y-axis to 25+- 0.1C or something else?

dpossin (posted 2019-07-17 08:25:15.0)

Dear customer, Thank you for your feedback. You can adjust the viewing range of the temperature graph by setting the range on the left hand side by setting the desired range in the field "Temperature Window".

Ingo Gersonde (posted 2019-03-26 05:01:19.65)

I use the MTD415TE on an evaluation board, applied to TEC and thermistor of a laser head. When i use the D_Share value, i get severe noise on the TEC current. Can one filter the temperatur signal or the TEC-output signal ? Thank you in advance Ingo Gersonde

swick (posted 2019-03-26 09:19:15.0)

This is a response from Sebastian at Thorlabs. Thank you for the feedback. The noise on TEC current could be caused by unshielded cables for the signal from Thermistor or D-Share value is set too high. In first case noise in sub-mV regime triggers D-share and in second case the value of D-share is too high in respect to P and I share. For improved noise immunity signals should be guided in shielded and twisted cables with reduced length. If PID values are not optimal please follow our guideline on the website at tab "PID Oscillation Test" or in the manual chapter 7. I contacted you directly for further troubleshooting.

Matthias.Nagel (posted 2018-08-06 15:53:41.887)

Can I drive 2 x ET-031-10-20 with the MTD1020T and th evaluation board?

nreusch (posted 2018-08-08 08:37:51.0)

This is a response from Nicola at Thorlabs. Thank you for your inquiry. I checked the voltage and current requirements of the Peltier element you mentioned: Maximum current is 2.5 A and maximum voltage 3.8 V. Therefore, you should be able to drive two elements in a series connection since the voltage drop across two elements is 7.8 V, i.e. lower than the specified 10 V for MTD1020T. Please note that the maximum output current of MTD1020T is 2.0 A, so it will not allow you to drive the elements at their maximum current. The recommended TEC elements for this driver are TECH3S, TECL4 and TECJ6. I will contact you directly to discuss further details of your specific application.

ward.becelaere (posted 2018-04-11 15:43:46.01)

According to the specs, the temperature range is between 5 and 45 C. For my application I need a range between 15 and 75 C. Is there any way to have an extended range? Maybe a different thermistor? Thanks!

swick (posted 2018-04-17 03:56:10.0)

This is a response from Sebastian at Thorlabs. Thank you for the inquiry. For OEM applications we offer customizations suitable to a wide range of requirements. Customization of the MTD1020T for an other temperature range is possible. We contacted you directly for further discussion.

xjiang225 (posted 2017-12-01 23:46:02.757)

I have installed the MTD software but could not find the device in the software("Scan USB" doesn't give any result). I can see the device as both COM port and USB port in device manager. The "POWER SUPPLY" LED3 is the only LED that is on on the board. Could you please suggest some possible issues that are causing this? Thanks!

swick (posted 2017-12-05 04:33:13.0)

This is a response from Sebastian at Thorlabs. Thank you for the inquiry. I have contacted you directly for troubleshooting.

user (posted 2017-11-15 09:58:43.903)

Can you share more information about the thermistor readout circuit; as well as the expected thermistor B constant? I need to design an interface circuit so that I can use a different type thermistor (R=9kOhm, B=~3400K)

mvonsivers (posted 2017-11-21 03:29:16.0)

This is a response from Moritz at Thorlabs. Thank you for your inquiry. Unfortunately, MTD415T can only be used with 10 kOhm thermistors. However, the MTD-Modules can be customized for high quantity orders. Please contact techsupport@thorlabs.com for further information.

mvonsivers (posted 2017-11-22 03:59:56.0)

This is a response from Moritz at Thorlabs. Our engineers have found a workaround for your problem. You can connect your 9 kOhm thermistor directly to the MTD415T module. In this case, you will get an offset between real temperature and read out value. This offset has to be taken into account when setting the set temperature. Our MTD modules are calibrated for a B constant [25/85°C] = 3950 K. Your slightly different B constant will lead to a non-linearity over the complete temperature range. If your application requires only temperature stabilization at one operating point you should still be able to find the right PID parameters. As already mentioned, for an OEM application we can modify and calibrate the MTD module according to your specifications.

rogier (posted 2017-09-29 17:38:09.133)

Hello, It seems that your current manual is not up-to-date. The programmers reference is saying that you should use quotations marks around the commands it seems with the new firmware update (1.0.5) on the MTD1020T this is no longer needed. The response isn’t written in brackets either as suggest in the manual.

swick (posted 2017-10-05 03:33:56.0)

This is a response from Sebastian at Thorlabs. Thank you for the inquiry. In the manual at chapter 5.1 you can find the nomenclature used for this device. The quotation marks or brackets are not part of the command or received message. This nomenclature makes it easier to distinguish between commands, received messages and formats. I will contact you directly for further assistance.

chkwak (posted 2017-08-11 15:07:47.68)

Hello I buyed MTD415TE, but this error message occur frequently, "TEC current was too long time on the limit without influence on the temperature." Let me know how to fix it.

mdiekmann (posted 2017-08-16 10:58:42.0)

This is a response from Meike at Thorlabs: Thank you for contacting us! This error typically indicates that the thermal load is too large for the module to handle. It is a safety feature to prevent the unit from overheating. We will contact you directly to troubleshoot the issue in your case.

slawomir.drobczynski (posted 2017-07-17 00:38:43.053)

I am using MTD415T and I would like to increase temperature from 25 to 36 degrees of Celsius. I start with factory default settings, why after few seconds TEC current is zero and Error Register: Thermal Latch-Up (TEC current at limit without temperature improvement) ?

wskopalik (posted 2017-07-20 06:01:23.0)

This is a response from Wolfgang at Thorlabs. Thank you very much for your feedback. Our MTD modules have a wide variety of safety features which can be en- or disabled by the costumer if needed. The ”Thermal-Latch-Up Error” prevents the cooling system from over-heating. The module measures the output power of the module and if no change in terms of TEC temperature is recognizable, the module switches the output off to prevent the system from over-heating. This can e.g. happen for very large thermal loads, because the change in temperature will happen very slow in this case. Please consider that the MTD415T is not designed to drive very large thermal loads. In normal operation this safety feature should not be triggered. As a workaround for your application, you could disable the corresponding safety bitmask. You need to send the command "S251" over a terminal program to the module for this. I will contact you directly to provide further assistance.

krevety (posted 2017-06-14 09:31:07.563)

Are you planning a replacement for MTDEVAL? btw. Excellent product, I like the MTD control app.

tcampbell (posted 2017-06-16 10:42:16.0)

Response from Tim at Thorlabs: Thank you for your feedback. Yes, we have been developing a replacement for the MTDEVAL and it should be available for purchase shortly.

j.zeludevicius (posted 2017-01-06 05:28:39.763)

I would like to express my two issues with MTDEVAL board and MTD415TE controller. I used this controller for temperature stabilization of pump laser diode in 14-pin butterfly package. Controller board was connected to NTC 10K thermistor and TEC. When I connected TEC leads correctly (+ to +, and - to -) I got erroneous behavior of the controller. It decreased temperature (up to minimum value) when the temperature had to be increased. I reversed TEC connection polarity and then It worked correctly. Could you check whether there is any error in controller design? Second issue is with operation status LED. When USB cable is disconnected the status LED turns off and it is not clear whether temperature control is active or is switch off as well. Could you comment on that? I have observed that status LED lights up whenever USB cable is connected to any source providing +5V, not necessary a computer.

swick (posted 2017-01-09 04:16:46.0)

This is a response from Sebastian at Thorlabs. Thank you very much for the feedback. Your description is exactly how the MTD modules are designed to work, your MTD module and the Evaluation board are working fine. Let me explain this in more detail: TEC: The described behavior, that you need to change the polarity of the TEC element is based on the mounting direction of your TEC element. You can change hot and cold site by changing the polarity of the lead wires or by changing the mounting direction of the TEC element itself. Please be aware, that Thorlabs cannot predict the mounting direction of each TEC element, so by changing the polarity of the lead wires you have the maximum flexibility. For your information: By using the MTD Software you will get an error code, which describes if the TEC element is connected in the wrong way. LED: Please refer to the manual for the function of the LED. The LED describes not if the MTD module is en- or disabled. It signals if the temperature is within the programmed temperature window. This is a very helpful feature to interface other (analog) circuitry to get a “Temperature Ready Signal”. To use this function correctly we recommend to adjust the “Temperature Window” and the “Temperature Protection Delay” in the right way. I will contact you directly for further assistance.

gtoner2506 (posted 2016-12-21 05:05:49.833)

I need to talk to this device using an embedded processor. Is ther a serial command set for it?

wskopalik (posted 2016-12-22 08:09:50.0)

This is a response from Wolfgang at Thorlabs. Thank you for your inquiry. These termperature controllers have an UART programming interface. A list of commands can be found in the manual from p.12 on. I will contact you directly to discuss your application in more detail.

cbrideau (posted 2016-12-06 14:37:03.893)

That was quick! The eval board looks great: Next challenge is to put connectors on this eval board and the LD eval board so you can put them together in a stack and share power supplies.

swick (posted 2016-12-07 03:17:26.0)

This is a response from Sebastian at Thorlabs. Thank you for the feedback. We will discuss your suggestion in our internal forum.

cbrideau (posted 2016-11-30 15:51:30.177)

Would be nice to see a daughter board and evaluation board for these like the MLD203 series laser drivers. An evaluation board that sockets one of the MLD203's AND one of these temperature controllers would be very handy for proto builders and evaluating the performance of the controllers.

tfrisch (posted 2016-12-02 02:42:40.0)

Hello, thank you for contacting Thorlabs. I have posted this in our internal engineering forum.