THORLABS MTD415T User manual

Data Sheet
Miniature Temperature Controller MTD415T
Features
· Small, safe and very high accuracy complete single-module controller
· High speed, ultra stable digital PID Loop
· Up to ± 1.5 A TEC current
· Very low output current noise
· Very small footprint (21.0 x 12.4 mm)
· Circuit Height 3.1 mm
· Supports 10 k W thermistor temperature sensor
· Single power supply operation
Applications
· Active cooling and temperature stabilization for a wide range of laser modules and diodes
· WDM, DWDM Laser-Diode Temperature Control
· EDFA Optical Amplifiers
· Temperature stabilization of photo detectors and photodiodes
· ATE
Short Description and Typical Application Diagram
The MTD415T is a compact and highly integrated temperature controller optimized for use in
high performance thermoelectric temperature control applications.
The on-chip power stage and the thermal control loop circuitry minimize external components
while maintaining high efficiency.
The output current is directly controlled to eliminate current surges. An adjustable TEC current
limit provides the highest level of TEC protection.
The MTD415T is operated from a single power supply and provides a bipolar ±1.5 A output by
connecting the TEC to the output of a bipolar power stage. True bipolar operation ensures
temperature control without “dead zones” or other nonlinearities at low TEC current values.
The digital control interface allows quick access to all system parameters as well as to digital
measurement data, this way enabling a simple integration into different systems.
MTD415T Data Sheet Rev. 1.0 1

Revision History
Revision
Changes with respect to previous revision
1.0
Initial Release
2MTD415T Data Sheet Rev. 1.0
MTD415T

© 2016 Thorlabs GmbH MTD415T Data Sheet Rev. 1.0 3
Contents
1 4Pin Configuration and Functions
2 6Technical Data
62.1 Absolute Maximum Ratings
62.2 Recommended Operating Conditions
72.3 Electrical Characteristics
3 8Typical Output Characteristics
4 9Functional Block Diagram
5 11Typical Application
6 12Programmers Reference
126.1 Nomenclature
126.2 Command Description
126.2.1 General Commands
136.2.2 TEC Commands
146.2.3 Temperature
156.2.4 Control Loop
176.2.5 Save Settings
176.2.6 Factory Default Settings
186.3 Error Register and Safety Bitmask
7 20PID Tutorial
8 22Troubleshooting
9 23Drawing
10 24List of Acronyms
11 25Warranty
12 26Copyright and Exclusion of Reliability
13 27Thorlabs 'End of Life' Policy
14 28Thorlabs Worldwide Contacts

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MTD415T Data Sheet Rev. 1.0
1 Pin Configuration and Functions
MTD415T Pin Configuration
Pin
Name
Description
1
VDD
Supply Voltage Input
Connect a + 4.5 V to 5.5 V power supply to VDD.
2
GND
Supply Voltage Ground
Connect the power supply ground connections to GND.
3
GND
Supply Voltage Ground
Connect the power supply ground connections to GND.
4
DNC
Do Not Connect
Do not connect this pin to any signal or potential. This pin is used for
manufacturing and test purposes.
5
DNC
Do Not Connect
Do not connect this pin to any signal or potential. This pin is used for
manufacturing and test purposes.
6
VREF
Reference Output Voltage for Thermistor Temperature Sensor
Connect this reference voltage output ( 1.8 V) to one end of the 10 k W
thermistor.
7
TEMP
Thermistor Temperature Sensor Input
Connect this pin to the other end of the 10 k W thermistor.
8
GNDS
Temperature Sensor Ground
Can be used for shielding purposes or left open.
9
GND
Supply Voltage Ground
Connect the power supply ground connections to GND.
10
ENABLE
Enable Signal Input (Low-Active)
Enable Input (Low = enabled, High = Disabled ), can be connected
directly to GND.
11
STATUS
Status Signal Output (Can be left floating)
Status Signal (High = temperature within defined temperature
window, Low = Temperature outside programmed temperature
window or an error occurred).
12
TX
Digital Interface Transmit Signal
UART Transmit Asynchronous Data Output. Connect this pin to the
RX pin of your application.

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1 Pin Configuration and Functions
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MTD415T Data Sheet Rev. 1.0
Pin
Name
Description
13
RX
Digital Interface Receive Signal
UART Transmit Asynchronous Data Input. Connect this pin to the TX
pin of your application.
14
GND
Supply Voltage Ground
Connect the power supply ground connections to GND.
15
TEC -
TEC Element negative connection
Connect this pin to the negative terminal of the TEC element.
16
TEC +
TEC Element positive connection
Connect this pin to the positive terminal of the TEC element.

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2 Technical Data
2.1 Absolute Maximum Ratings
Supply Input Voltage
4.5 V to 6 V
Supply Input Current
1.6 A
TEC Output Current
-1.5 A to 1.5 A
TEC Compliance Voltage
4.0 V
Maximum Output Power
6.0 W
Power Dissipation
1.5 W
Pin Voltage Range 1)
VDD
ENABLE, RX, TEC-, TEC+
TEMP
-0.3 V to 6 V
-0.3 V to (VDD + 0.3 V)
-0.3 V to 3.3 V
Maximum Output Current STATUS, TX
10 mA
Maximum Input Current ENABLE, RX
10 mA
Operating Temperature
-40 °C to + 70 °C
1) All voltages with respect to network ground terminal.
Notes
(1) Above specifications are given for the free-air operating temperature range unless
otherwise noted.
(2) Stresses beyond those listed above may cause permanent damage to the product. These
are stress ratings only; functional operation of the MTD415T at these or any other
conditions beyond those indicated under Recommended Operating Conditions and
Electrical Characteristics is not implied.
(3) Operation beyond the maximum rated conditions for extended periods may affect product
reliability.
2.2 Recommended Operating Conditions
Supply Voltage
4.5 to 5.5 V
Operating Temperature
-20 to + 60 °C
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2 Technical Data
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2.3 Electrical Characteristics
TEC Current Output
Output Current
up to ±1.5 A into 2.66 W TEC - see diagram on page .
Compliance Voltage
4.0 V
Output Power
up to 6.0 W
Measurement Resolution
better than 8 mA, typ. 3 mA
Measurement Accuracy
± 50 mA
Noise and Ripple (typ.)
< 10 mA 1)
TEC Current Limit
Setting Range
0 to 1.5 A
Setting Resolution
1 mA
Setting Accuracy
± 50 mA
Temperature Sensor
Supported Sensor
10 k W Thermistor 5)
Maximum Temperature Control Range 2)
+ 5 °C to + 45 °C
Temperature Setting Resolution
1 mK
Temperature Measurement Resolution 3)
better than 10 mK; typ. 2 mK
Absolute Temperature Accuracy 2)
± 0.5 °C
Temperature Stability over 8 h, typ.
better than 20 mK
Temperature Coefficient
< 20 mK/°C
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
General Data
Safety Features
· TEC Current Limit
· Sensor Fault Protection
· TEC Open Circuit Protection
· Temperature Setpoint Limit
· Temperature Window Protection Delay
· Over Temperature Protection
Operating Temperature
-20 °C to +60 °C 4)
Storage Temperature
-40 °C to +100 °C 4)
Warm-Up Time for Rated Accuracy
10 min
Dimensions (W x H x D)
21 x 12.4 x 3.1 mm³
Approx. Weight
2 g
1) Measured with a TEC element with an equivalent resistance of 4
W .
2) Control range and thermal stability depend on thermistor parameters.
3) Maximum measurement resolution depends on cycle time settings. Please refer to Programmers Reference.
4) non-condensing
5) Use only thermistors with 10k
W resistance at 25 °C (R25°C). Resistance Measurement Range: 4.2 to 29 k W
All technical data are valid at 23 ±5 °C and 45 ±15% rel. humidity (non condensing)
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3 Typical Output Characteristics
Notes
1. The maximum TEC current of 1.5 A can be delivered into a load resistance of 2.66 W at
recommended operating conditions.
2. At higher load resistance, the maximum output current drops due to compliance voltage
limitation.
3. The maximum output current at lower than 2.66 W load resistance (colored range) depends
on environmental conditions.
Notes
1. The maximum output power of 6 W can be delivered into a load resistance of 2.66 W at
recommended operating conditions.
2. The maximum output power at lower than 2.66 W load resistance (colored range) depends
on environmental conditions.

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4 Functional Block Diagram
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MTD415T Data Sheet Rev. 1.0
4 Functional Block Diagram
Functional Block Diagram MTD415T
Principle of Operation
In general, a temperature controller (within the blue frame) is a closed loop system. A
temperature sensor measures the temperature of the controlled object (e.g., a laser diode).
This actual temperature signal is amplified and compared with the temperature set value.
The differential signal out of the comparator controls then the current of the thermoelectric
cooler in order to maintain the temperature of the object constant. Ideally, the temperature
settling is carried out in the shortest times, with minimum settling error and without temperature
overshoots.
A thermoelectric coolers is a Peltier element that produces a temperature gradient depending
on the current direction trough the TEC. For this reason, the TEC current must be bidirectional.
In order to adapt the control loop to different thermal loads, and to optimize the temperature
controller's response characteristics, a PID amplifier is used. Closer information please see in
the PID Tutorial (page )
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Functional Description
The MTD415T is a miniature, closed-loop temperature controller module. It is compatible with a
10 k W NTC (thermistor) temperature sensor and it's output is designed for control of
thermoelectric coolers (TEC).
The MTD415T delivers a TEC current up to 1500 mA at 4.0 V compliance voltage.
Power Supply
The supply voltage ranges from 4.5 V to 5,5 V. From the supply voltage, the internal supply
voltage for the microcontroller is derived. Further, a reference voltage for the temperature
sensor is generated (VREF; 1.8 V).
TEC Current Control
The TEC element is connected between TEC+ and TEC-. A correct connection is essential to
avoid wrong temperature correction.
The MTD415T allows to limit the maximum TEC current. Lowering the TEC current limit might
be helpful for control loop optimization in case of low thermal loads and lowers the dissipated
by the MTD415T power.
Micro-controller
The functions of the microcontroller are:
· Comparison of the actual temperature with the set temperature;
· Generation of the control signal for TEC output stage with respect to the comparator
signal;
· PID loop control for optimization of the temperature settling time and for minimizing the
final temperature error.
All parameters (TEC current limit, set temperature, temperature window, PID share settings
etc.) are programmed via the UART user interface. Detailed information about how to program
the MTD415T can be found in the section Programmers Reference on page .
Note
The UART interface uses 3.3 V logic level. Connect the UART to a PC only using an
appropriate converter, e.g., a commercially available UART-to-USB cable.
The Status signal informs about correct operation.
The temperature control is activated by setting the Enable pin to low.
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5 Typical Application
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5 Typical Application

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6 Programmers Reference
6.1 Nomenclature
Program messages are written
in inverted commas:
"A?"
"Lx" (x - Parameter)
Response messages are written in brackets:
[-800 <LF>]
Data Format
Numerical value with sign in integer notation:
-220 or 16789432.
Command /response Terminator:
Line Feed (<LF>)
6.2 Command Description
6.2.1 General Commands
Command
Explanation
Response Example
"m?"
Reads the version of hardware and software
[MTD415T FW0.6.8]
Command
Explanation
Response Example
"u?"
Reads the UUID (Universal Unique Identifier) of the MTD415T
[045F778655FDE5118ED499C9B4521485]
Command
Explanation
Response Example
"E?"
Reads the Error Register. Responses
see section Error Register and Safety Bitmask
"c"
Resets the Error register
Note
The MTD415T has a non-volatile memory (flash) that stores the setting parameters. This
memory has a limited number of erase / write cycles. In order to protect the flash memory,
changes to setting parameters are not stored automatically. If you want to keep parameter
changes after power-down of the MTD415T, save them to the flash memory using the "M"
command. This command saves the T, W, L, d, G, O, P, I, D, C and S parameters at a time.
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6 Programmers Reference
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MTD415T Data Sheet Rev. 1.0
6.2.2 TEC Commands
Command
Explanation
Response Example
Programming
"Lx"
Sets the TEC current limit to x *)
Value range x: 200 to 2000 [mA]
Reading
"L?"
Reads the TEC current limit
[x<LF>][mA]
"A?"
Reads the actual TEC current
[x<LF>][mA]
x < 0: Heating; x > 0: Cooling
"U?"
Reads the actual TEC voltage
[x<LF>][mV]
*) This set value remains during the actual power-on cycle. Use the "M" command to save it to the non-volatile
memory.

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MTD415T Data Sheet Rev. 1.0
6.2.3 Temperature
Command
Explanation
Response Example
Programming
"Tx"
Sets the set temperature to x *)
Value range x: 5000 to 45000 [10-3 °C]
Reading
"T?"
Reads the set temperature
[x<LF>]
Value range x: 5000 to 45000 [10-3 °C]
"Te?"
Reads the actual temperature
[x<LF>]
Command
Explanation
Response Example
Programming
"Wx"
Sets the set temperature window to x *)
Value range x: 1 to 32768 [mK]
Reading
"W?"
Reads the temperature window
[x<LF>][mK]
Command
Explanation
Response Example
Programming
"dx"
Sets the delay time between reaching the temperature window
and activating the Status output pin to x *)
Value range x: 1 to 32768 [sec]
Reading
"d?"
Reads the delay time between reaching the temperature
window and activating the Status output pin
[x<LF>][sec]
*) This set value remains during the actual power-on cycle. Use the "M" command to save it to the non-volatile
memory.

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6 Programmers Reference
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MTD415T Data Sheet Rev. 1.0
6.2.4 Control Loop
Loop Test
Command
Explanation
Response Example
Programming
"Gx"
Sets the critical gain to x *)
Value range x: 10 to 100000 [mA/K]
Reading
"G?"
Reads the critical gain
[x<LF>][mA/K]
Command
Explanation
Response Example
Programming
"Ox"
Sets the critical period to x *)
Value range x: 100 to 100000 [msec]
Reading
"O?"
Reads the critical period
[x<LF>][msec]
PID Settings
Command
Explanation
Response Example
Programming
"Cx"
Sets the cycling time to x *)
Value range x: 1 to 1000 [msec]
Reading
"C?"
Reads the cycling time
[x<LF>][msec]
Command
Explanation
Response Example
Programming
"Px"
Sets the P Share to x *)
Value range x: 0 to 100000 [mA/K]
Reading
"P?"
Reads the P Share
[x<LF>][mA/K]
*) This set value remains during the actual power-on cycle. Use the "M" command to save it to the non-volatile
memory.

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Command
Explanation
Response Example
Programming
"Ix"
Sets the I Share to x *)
Value range x: 0 to 100000 [mA/(K+sec)]
Reading
"I?"
Reads the I Share
[x<LF>][mA/(K+sec)]
Command
Explanation
Response Example
Programming
"Dx"
Sets the D Share to x *)
Value range x: 0 to 100000 [(mA*s)/K]
Reading
"D?"
Reads the D Share
[x<LF>][(mA*sec)/K]
*) This set value remains during the actual power-on cycle. Use the "M" command to save it to the non-volatile
memory.

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6 Programmers Reference
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MTD415T Data Sheet Rev. 1.0
6.2.5 Save Settings
Command
Explanation
Response Example
"M"
Saves the setup. The actual parameters that have been set
using the commands T, W, L, d, G, O, P, I, D, C and S, are saved
to the nonvolatile memory.
6.2.6 Factory Default Settings
Parameter
Explanation
Factory Default
L
TEC current limit
1000 mA
T
Temperature set value
25 °C
W
Temperature window
1000 mK
d
Temperature window delay
10 sec
C
Cycle time PID loop
50 msec
P
P share PID loop
1000 mA/K
I
I share PID loop
200 mA/(K*sec)
D
D share PID loop
100 (mA*sec)/K
G
Critical PID loop gain (Loop test)
2000 mA/K
O
Critical PID loop oscillation period (Loop test)
2000 msec
S
Value of the Safety Bitmask
255

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6.3 Error Register and Safety Bitmask
The MTD415T has an internal 16 bit error register:
Bit Number
Event
0
Enable pin not set to L (GND)
1
Internal temperature too high
2
Thermal Latch-Up (TEC current at limit without temperature improvement)
3
Cycling time too small
4
No Sensor detected
5
No TEC detected (connection open)
6
TEC mispoled
7
(not used)
8
(not used)
9
(not used)
10
(not used)
11
(not used)
12
(not used)
13
Value out of range
14
Invalid command
15
(not used)
The error register can be read out using the "E?" command. The error register can be reset
using the "c" command or by setting the Enable pin to Off and On again.

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MTD415T Data Sheet Rev. 1.0
Further, with default setting of the Safety Bitmask (value = 255), the states of bits 0 to 7 are
handed over to the Status output pin - if any of the bits 0 to 7 is H, the Status level is "LOW"
and the TEC Current Output is switched off.
The Safety Bitmask can be used to mask any desired error at the Status output pin.
Attention
Masking an error may lead to damage of the MTD415T. For example, if bit 1 is masked,
exceeding the internal temperature will not be reflected on the status pin as an error and the
TEC output will not be disabled!
The safety bitmask can be programmed:
Command
Explanation
Response Example
Programming
"Sx"
Sets the Safety Bitmask to x
Value range x: 0 to 32768
Reading
"S?"
Reads the Safety Bitmask value.
[x<LF>]
Note
If the safety bitmask should be saved for future use, it needs to be memorized using the "M"
command.

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MTD415T Data Sheet Rev. 1.0
7 PID Tutorial
The general requirements to a temperature control loop are:
· fastest settling time after power on or changing the set temperature
· minimum residual temperature error
· settling without temperature overshoots
· fastest response to changes of the thermal load
PID amplifiers can fulfill these requirements. Temperature control loops are comparatively slow;
control oscillations appear with a frequency in the range of several Hz or parts of Hz. The PID
adjustment allows to optimize the dynamic behavior.
The P share is the proportional share, or the gain of the amplifier, that defines the settling time.
The higher the P share, the faster the settling and the less residual temperature error. The
downside is that high P shares lead to oscillations.
The I share is the integrating share of the amplification, or the gain at low frequencies. It allows
to minimize the residual temperature error.
Optimal settings of the P and I shares result in a fast approach to the set temperature, without
oscillations and with a minimum residual temperature error. However, such a loop is not able to
quickly react to sudden changes of the thermal load, for example, if a thermally stabilized laser
diode is set to a higher or lower output power that changes the laser's heat dissipation. The D
share (differential share, or the gain at high frequencies) allows the system to quickly react to
temperature changes, without generating oscillation of the temperature around the set point.
The MTD415T microcontroller 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. Below an example procedure is explained in detail.
Example of a PID adjustment
Pre-conditions:
· TEC current limit is set correctly
· all connections are made properly
In order to observe the temperature change, connect an appropriate instrument that allows to
display the temperature change vs. time, to the TEMP input of the MTD415T.
1. Configure the PID loop:
Set temperature = 25°C: "T25000"
P share = 1000 mA/K: "P1000"
I share = 0: "I0"
D share = 0: "D0"
Cycle time = 30 ms: "C30"
2. Enable the TEC. The actual temperature Te approximates the set value.
3. Now, find the critical P share (critical gain) value at which the system starts to oscillate for a
minimum of 20 cycles without amplitude drop as a reaction to a changed set temperature.
An example procedure is described below:
· Set P to 10.000 mA/K: "P10000".
In order to trigger loop oscillation, increase the set temperature for 0.1 K: "T25100"
· Lower P to 5.000 mA/K: "P5000", decrease the set temperature for 0.1 K: "T25000"
and observe the loop behavior.
· If the loop still oscillates, lower the P share again, change the set set temperature for
0.1K and observe the loop behavior.