Analog Technologies TEC50V20AB User manual

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Analog Technologies
TEC50V20AB
High Voltage High Current TEC Controller
Figure 1. Physical Photo of TEC50V20AB
FEATURES
Built-in Smart Auto PID Control –the World’s First
Power Supply Voltage: 50V
High Output Voltage: ±40V
High Output Current: 20A
High Efficiency: > 92%
@VVPS = 50V & VTEC = 25V & ITEC = 20A
High Temperature Stability: < ±0.001°C
Low Thermistor Injection Current: < 1µA
Continuous Bi-directional Output
Programmable Output Current and Voltage Limits
Real Time Temperature, Current and Voltage Signals
Selectable Temperature Sensor Types: thermistor,
RTD, or temperature sensor IC
High Reliability and Zero EMI
Compact Size: 63(L) ×61(W)×16.7(H) (mm)
100 % Lead (Pb)-free and RoHS Compliant
APPLICATIONS
Driving high power TEC modules at high efficiency.
DESCRIPTION
TEC (Thermo-Electric Cooler) is a semiconductor device
which can cool down or heat up the temperature of an
object by injecting an electrical current in one or the other
direction. This TEC controller, TEC50V20AB, is
designed to drive a TEC at high efficiency for regulating
the object temperature precisely by controlling the
direction and magnitude of the current going through the
TEC. It is powered by a DC voltage between 10V to 50V
and the output current can go up to 20A without using a
heat sink. Figure 1 is the photo of the TEC controller
TEC50V20AB, Pin 1 to pin 18 shows the signal pins, and
the others are power pins. See Figure 2.
The controller TEC50V20AB allows setting the set-point
temperature, maximum output voltage magnitude, and the
maximum output current magnitude respectively. These
three settings are the input parameters for the three control
loops: constant temperature, constant current, and
constant voltage. Before hitting the maximum output
voltage magnitude or the maximum output current
magnitude, the temperature loop is in control. When
hitting the maximum output voltage magnitude, either
outputting a positive or negative value across the TEC, the
voltage loop takes over the control, the controller will be
outputting a constant voltage to the TEC; when hitting the
maximum output current magnitude, the current loop
takes over the control, the controller will be outputting a
constant output current to the TEC. The highest output
voltage magnitude is limited by the maximum power
supply voltage, and the maximum output current
magnitude is 20A.
The temperature signal can be obtained by using one of
these 3 temperature sensors: thermistor, RTD or
temperature sensor IC. When using a thermistor, the set-
point temperature range is determined by an external
temperature network formed by 3 resistors. In order to
reduce the injection current to the thermistor to reduce the
errors caused by the self-heating effect, the injection
current is provided in pulse mode, reducing the current by
10 times as opposed to a continuous current.
One advanced feature of this TEC controller is that it
comes with a smart auto PID control micro-processor, it
continuously senses and compensates for the thermal load
automatically. No need to use any external components for
forming a compensation network, nor requires tuning.*
*Firmware PID control –currently not available.
Conservative users can still select the conventional analog
compensation network. The same as in the past, it requires
a onetime pre-tuning network to match the thermal load,
but provides reliable and high accuracy control. For fixed
thermal load applications, conventional analog
compensation can be selected; while for applications with
variable or multiple different thermal loads –one type at a
time, the automatic PID control is more suitable.

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Analog Technologies
TEC50V20AB
High Voltage High Current TEC Controller
Figure 2 is the top view of the controller, showing the pin
names and the locations. There are a total of 22 pins. Pins
No.1 to No.18 are control input or indicator output signals;
the rest of the pins are power inputs or outputs. The pin
function details are given in Table 1.
At the thermistor input, there is a linearization circuit for
the thermistor, to make the temperature output voltage be
more linearly proportional to the actual thermistor
temperature. There is a voltage inverter circuit, and it
makes the temperature output voltage be positively
proportional to the temperature, since the thermistor has a
negative temperature coefficient. These 2 circuits together
are called temperature measurement circuit. See Figure 6.
The set-point temperature voltage and the voltage
representing the actual temperature are sent to an error
amplifier. There is a compensation network inserted in the
loop, to stop the oscillation of the controller caused by
phase delay effects of the thermal load. Therefore, the
compensation network must match the need for driving a
particular thermal load. To simplify the tuning, a tunable
compensation network is provided by the evaluation board
for this TEC controller. Of course, users can also use an
external compensation network if they need it. A detailed
guidance about how to tune the compensation network
with a thermal load is given in the evaluation board
application note.
20
19
21
22
Case
TEC50V20A VPS
PGND
TEC+
TEC−
RTH
GND
18
17
SNCO
TMGD
SBDN
GND
4VR
TMS
IN+
RTH
IDR
CMIN
TMO
ILM
VLM
ITEC
VTEC
CTMO
5
6
7
8
9
10
11
12
13
14
1
2
3
4
16
15
Figure 2. Pin Names and Location
SPECIFICATIONS
Table 1. Pin Function Descriptions
Pin #
Name
Note
Description
1
SNCO
Digital output
Synchronization output. This pin outputs a switching pulse signal, from 0V to
5V, 600kHz. It can be sent to the synchronization input of another SM (Switch
Mode) controller or power supply, to eliminate the beating interference
between this TEC controller and the other SM device.
2
TMGD
Digital output
Temperature good indication. Active high. Indicates when actual temperature
equals to the set-point temperature of the target object. That is, the target object
temperature is within 0.001°C away from the set-point temperature, provided
the set-point temperature range is 40°C. Or VTMOVTMS< 0.5mV.
3
SBDN
Analog
/Digital input
Standby and shut down control. This SBDN pin is internally floated and series
with 1k resistor. It’s suggested to pull this pin up to VPS power supply by a
4.99MΩ resistor. If pulled to ground, it shuts down the entire controller. This
pin has 2 threshold voltages: 1.5V and 2.0V. See Figure 5.
SHUT DOWN: VSBDN < 0.3V, the controller is set to non-working state.
STANDBY: 1.9V＞VSBDN＞1.5V, all components are set to working state
except the output stages for TEC+ and TEC.
OPERATION: VSBDN＞2.0V, the whole controller is set to working state.
4
GND
Ground
Signal ground. Connect this pin to the signal ground of ADCs, DACs, and the
signal sources. It can also be used as analog output pin ground.

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
5
4VR
Analog
output
Reference voltage output, 4.096V. It can be used as the voltage reference by the
potentiometers or DACs for setting the analog ports, such as TMS, ILM, VLM,
etc. It can also be used by ADCs for sensing the analog output ports: TMO,
CTMO, ITEC and VTEC. The initial accuracy is 0.1%, and the temperature
coefficient is <50ppm/°C max.
6
TMS
Analog input
Analog Input port for setting the set-point temperature for the target object. It
is internally tied a 1MΩ resistor to the half value of the reference voltage, 2V.
The open circuit voltage of this pin is thus 2V, corresponding to a set-point
temperature of 25°C by using the default temperature network (with the set-
point temperature range being from 15°C to 35°C). It is highly recommended to
set this pin’s voltage by using the controller’s 4V voltage reference. This pin
can be set by using a POT or DAC. When the set-point temperature needs to be
at 25°C, leave this pin unconnected.
7
IN+
Analog input
Receive external temperature signal (thermistor and temperature sensor, etc.)
8
RTH
Analog input
Thermistor connection port. Connect to the thermistor which is mounted on the
target object for sensing its temperature. By using the default internal
temperature network, a 10kΩ @ 25°C thermistor can be used. Other type of
thermistors or temperature sensors can also be used, see the application section
for details.
9
TMO
Analog
output
Actual target object temperature indication. It swings from 0V to 4V. By using
a default internal temperature network, it represents 15°C to 35°C when this
pin’s voltage swings 0.1V to 3.9V linearly, provided a standard 10kΩ
thermistor is used as the temperature sensor device.
10
CMIN
Analog input
Compensation input pin for the thermal control loop.
11
IDR
Analog input
and output
This voltage is derived from the temperature error detection circuit and used as
the input control signal of the current loop for the TEC. Its internal impedance
is 10kΩ and can be over-driven by an external analog signal which is able to
over-ride the 10kΩ resistor. The voltage range is from 0V to 4V, corresponding
to 20Ato +20Aoutput current. Setting this pin voltage to 2V forces the output
current to zero.
12
ILM
Analog input
This pin sets the TEC Current Limit. The maximum limit current is 20A.
Setting this pin’s voltage from 0V to 4V corresponds to setting the current
magnitude limit from 0A to 20A: VILM =
75.3
)( MAX
OUT AI
13
VLM
Analog input
This pin sets the TEC voltage Limit. The maximum limit voltage is 50V. Setting
this pin’s voltage from 0V to 4V corresponds to the TEC voltage magnitude
limit being from 0 to 50V: VVLM =
5.7 MAX
TECTEC VV  

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
14
ITEC
Analog
output
TEC current indication. ITEC is an analog voltage output pin with a voltage
proportional to the actual current through the TEC. ITEC’s center voltage is 2V,
corresponding to zero current through the TEC.
VITEC =
5.7 )(AIOUT
+2V, where IOUT is the actual output current of the controller,
flowing out from TEC+ port and flowing in to TECpin.
15
VTEC
Analog
output
TEC voltage indication. VTEC is an analog voltage output pin with a voltage
proportional to the actual voltage across the TEC. It swings from 0V to 4V to
indicate the output voltage being from 50V to 50V, so the center voltage is
2V.
VVTEC =
15  TECTEC VV
+2V
16
CTMO
Analog
output
The controller internal temperature indication output. It can be used for sensing
the actual temperature of the controller, to avoid over-heating.
17
GND
Ground
Signal ground. Connect this pin to the signal ground of ADCs, DACs, and the
signal sources. It can also be used as analog output pin ground.
18
RTH
Analog input
Thermistor connection port. Connect to the thermistor which is mounted on the
target object for sensing its temperature. By using the default internal
temperature network, a 10kΩ @ 25°C thermistor can be used. Other type of
thermistors or temperature sensors can also be used, see the application section
for details.
19
TEC+
Analog power
output
This pin is used to connect to the front end of the TEC module to improve the
current capability.
20
TEC−
Analog power
output
This pin is for connecting to the negative terminal of the TEC module.
21
PGND
Power ground
Power ground for connecting to the power supply 0V return node.
22
VPS
Power input
Power supply voltage positive node. The normal operating voltage range is 15V
to 50V, the maximum value is 50V.
S1
Dial the code
switch
Set the controller to different states and choose different types of temperature
sensors to use
S4,S5,S6
,S7,S8
Dial the code
switch
Adjustment approach for resistors (Rd, Ri and Rp) and capacitors (Cd and Ci).
See Table 4 for switch function details.

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
Table 2. Electrical characteristics.
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Units
Reference Voltage
V4VRSOUT
TA= 25°C
4.0925
4.096
4.0995
V
Initial Error
VE
TA= 25°C
−0.05
0.05
%
Temperature Coefficient
TC
±3
±8
ppm/°C
Maximum Load Current
I4VRMAX
TA= 25°C
−20
+20
mA
Switch frequency
F4VRS
83
85
87
Hz
Output Voltage (Open circuit)
VSNCOOUT
Open circuit voltage =
0V ~ 4V PWM
0
4
V
Voltage Range (with load)
VSNCOOUT
Open circuit voltage =
0V ~ 4V PWM
0.1
3.9
V
Frequency
FSNCO
Open circuit voltage =
0V ~ 4V PWM
600
kHz
Temperature Good Indication: TMGD pin, pin 2
Voltage Range (Open circuit)
VTMGDOUT
Open circuit voltage =
4V
0
4
V
Voltage Range (with load)
VTMGDOUT
Open circuit voltage =
4V
0
4
V
Maximum Sourcing Current
ITMGDSC
Open circuit voltage =
4V
1
15
mA
Maximum Sourcing Voltage
VTMGDSC
Open circuit voltage =
4V
3.7
4
V
Maximum Sinking Current
ITMGDSK
Open circuit voltage =
4V
3
20
mA
Maximum Sinking Voltage
VTMGDSK
Open circuit voltage =
4V
0
0.6
V
Standby Shutdown Control: SBDN pin, pin 3
Input Current
ISBDNIN
VSBDN = 0V
0.1
0.3
µA
VSBDN = 4V
4
6
VSBDN = 50V
50
50
Input Voltage Range
VSBDNIN
Open circuit voltage =
5V
0
50
V

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
Shutdown Logic Low
VSBDNSDL
Open circuit voltage =
5V
0
V
Shutdown Logic High
VSBDNSDH
Open circuit voltage =
5V
0.7
V
Standby Logic Low
VSBDNSBL
Open circuit voltage =
5V
1.4
V
Standby Logic High
VSBDNSBH
Open circuit voltage =
5V
1.9
V
Operation Logic Low
VSBDNOPL
Open circuit voltage =
5V
2.0
V
Operation Logic High
VSBDNOPH
Open circuit voltage =
5V
5
V
Reference Voltage Output: 4VR pin, pin 5
Output Voltage Range
V4VROUT
TA= 25°C
4.0925
4.096
4.0995
V
Initial Error
VE
TA= 25°C
0.05
%
Temperature Coefficient
TC
TA= −40°C ~ 125°C
3
8
ppm/°C
Maximum Load Current
I4VRMAX
TA= 25°C
−20
+20
mA
Maximum Load Capacitance
C4VRMAX
0.1
1
uF
Temperature Set: TMS pin, pin 6
Input Impedance (See Figure 3 in
Page 8 for input equivalent circuit)
ZTMSIN
5
MΩ
Input Voltage Range
VTMSIN
0
4
V
Open Circuit Voltage
VTMSOP
2
V
Temperature Signal Input: IN+ pin, pin 7
Input Voltage Range
VIN+
0
4
V
Thermistor Connection Port: RTH pin, pin 8, pin 18
Input Voltage Range
VRTHIN
0
4
V
Actual Target Object Temperature Indication: TMO pin, pin 9
Output Voltage Range
VTMOOUT
RLOAD = 10kΩ to 2V
−40°C≤ TA≤ +125°C
0
4
V
Output Current
ITMOOUT
VSS = 0V
−12
12
mA

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
TA= 25°C
Compensation Input: CMIN pin, pin 10
Input Voltage Range
VCMIN
RLOAD = 10kΩ to 2V
−40°C≤ TA≤ +125°C
0
4
V
Input Current
ICMIN
−40°C≤ TA≤ +125°C
90
200
pA
Compensation Output: IDR pin, pin 11
Output Voltage Range
VIDROUT
RLOAD = 10kΩ to 2V
−40°C≤ TA≤ +125°C
0
4
V
TEC Current Limit: ILM pin, pin 12
Input Impedance
ZILM
21
kΩ
Input Voltage Range
VILMIN
0
4
V
TEC Voltage Limit: VLM pin, pin 13
Input Impedance (See Figure 4 in
Page 8 for input equivalent circuit)
ZVLM
10
kΩ
Input Voltage Range
VVLMIN
0
4
V
TEC Current Indication: ITEC pin, pin 14
TEC Voltage Indication: VTEC pin, pin 15
Controller Temperature Indication: CTMO pin, pin 16
Output Voltage Range
VCTMO
TA= 25°C
0
4
V
Maximum Load Current
ICTMOOUT
TA= 25°C
−12
12
mA
TEC+/TEC− pin, pin 19/pin20
Maximum Output Current
|IMAXTEC+|
|IMAXTEC-|
VPS = 50V
TA= 25°C
0
20
A
Maximum Output Voltage
|VOUTMAX|
VVPS = 50V
0
40
V
Power Supply Input: VPS pin, pin 22
Input Voltage Range
VVPS
5
50
V
Input Current
IVPS
Operation mode
0.05
16
A
IVPSSB
Standby mode
5
20
mA
IVPSSD
Shutdown mode
50
µA

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
Temperature Stability
Temperature Error Voltage
VTMO−VTM
S
−0.47
0.02
0.47
mV
Efficiency
η
VVPS = 50V
|VTEC+−VTEC−| = 14V
|ITEC+−ITEC−| = 20A
≥92
%
Case Operating Temperature Range
TCS
−40
110
°C
Ambient Operating Temperature
Range
TA
−40
65
°C
Storage Temp. Range
TSTG
−40
125
°C
Controller Case Thermal
Resistance
RTH
9
°C /W
This TEC controller can only drive the TECs having >1Ω impedance, which equals VMAX / IMAX.
4VR
TMS TEC50V20A
1MΩ1MΩ
Figure 3. TMS Input Equivalent Circuit
4VR
R1
R2
S2
2.2uF
ADC
ADC
Control
C1
RVLM2
VLM
GND
20k
RVLM1
1k
Figure 4. VLM Input Equivalent Circuit
The switch S2 is closed @ heating, and open @ cooling

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
Controller State
Operation
Standby
Shutdown
VSB-OP
VOP-SB
VSD-SB
VSB-SD
Figure 5. Controller States
VSB-SD: Going down logic low from standby to shutdown
VSD-SB: Going up logic high from shutdown to standby
VOP-SB: Going down logic low from operation to standby
VSB-OP: Going up logic high from standby to operation
BLOCK DIAGRAM
The block diagram of the controller is shown in Figure 6.
Temperature
Measurement
Circuit
Bi-directional
Current
Output
H-Bridge
Error
Amplifier
With
Compensation
Network
Output
Voltage
Control
Circuit
Temperature
Monitor
Circuit
Current
Limit
Control
Circuit
TEC
Temperature
Output
Voltage
Current
Control
Output
Set-point Temp. Temp. Good Indication
Temp. Output
Figure 6. TEC Controller Block Diagram

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
APPLICATIONS
TEC controller connections are shown in Figure 7.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
18
17
W1 20k
Clock wise
From microprocessor
To microprocessor
Synchronization output
12V ~ 50V
To power GND
TEC
SNCO
TMGD
SBDN
GND
4VR
TMS
IN+
RTH
TMO
CMIN
IDR
ILM
VLM
ITEC
VTEC
CTMO
PGND
20
19
TEC+
TEC−
VPS
Voltage reference
To external signal
Thermistor
W2 20k
Clock wise
20k
Clock wise
W3
Compensation
network
To ADC
To ADC
To ADC
R1 R2
RI
RP
RD
CI
CD
R3
Figure 7. TEC Controller Connection

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
SBDN
Table 3. External Detector Selection.
No.
Input
Voltage
External Detector
1
SBDN
0V ~ 0.5V
SD
2
SBDN
1.5V ~ 1.9V
SB
3
SBDN
2V ~ 2.3V
Temperature sensor
4
SBDN
2.4V ~ 2.7V
RTD/RTH
5
SBDN
2.8V ~ 4V
RTH (pulse mode)
Temperature Sensor Selections
There are usually three temperature sensors, thermistor,
RTD (Resistance Temperature Detector), and IC
(Integrated Circuit) temperature sensors.
1. Thermistor
+
−
RTH
TMO
4VR
RTH
R2 R3
R1
R5
R4
IRTH
Figure 8. Thermistor
To achieve the required VTMO outputs at the three
different setting point temperatures in the Temperature
Network, use the equation:

MIDLOWHIGH
LOWHIGH
HIGHLOW
MID
MID RRR RRRRR
RR 


2
2
1
(1)
MID
RRR  12
(2)
 
MIDLOW
MIDLOW
RR RRRR
R

11 3
(3)
For example, setting the high set-point temperature at
35°C and the low set-point temperature at 15°C results in
a middle set-point temperature (35 + 15)/2 = 25°C . Use
the R-T table of a thermistor.
RHIGH = 6.9kΩ
RMID = 10kΩ
RLOW = 14.8kΩ
Note that Equation 1 to Equation 3 result in
R1 = 17.5kΩ
R2 = 7.5kΩ
R3 = 81.3kΩ
In order to reduce the injection current to the thermistor
to reduce the errors caused by the self-heating effect, the
injection current is provided in pulse mode, reducing the
current by 10 times as opposed to a continuous current.
It’s recommended to connect R1 to SNCO, and the
controller will measure temperature at intervals that will
reduce the error caused by the RTH self-heating. At the
same time, the SBDN pin should be between 2.8V and
4V. See Table 3.
We can also connect R1 to 4VR, but it may lead to some
errors caused by RTH self-heating. At the same time,
SBDN pin should be between 2.4V and 2.7V. See Table
3.
2. RTD
RTD is short for resistance temperature detector, which
features high accuracy and low drift. It usually generates
heat when the current flows through the RTD, which is
called self-heating effect. Moreover, RTD has an
approximate linear resistance-temperature relationship.

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
RTD R4
R1
4VR
+
−
TMO
IN+
RTH
R3
R2
Figure 9. RTD
VTMO
(V)
3.9
TLTUT
0.1
Figure 10. Linear Relationship between VTMO and
Temperature
RTD = R0×(1+0.00385T)
e.g. R0= 1kΩ
When T = 10°C, RTD(10) = 1.0385kΩ
When T = 40°C, RTD(40) = 1.154kΩ
Choose R1
A. PRTD≤1mW, RTD = 1000Ω
PRTD = (IRTD)2×1000Ω = 0.001W
IRTD = 1mA =
TD
R+R1
4VR
=
1k+R14
R1=3kΩ
B. PRTD≤1mW, RTD = 100Ω
PRTD = (IRTD)2×100Ω = 0.001W
IRTD = 3.16mA =
TD
R+R1
4VR
=
0.1k+R1 4
R1=1.15kΩ
VTMO =
R2
R4×4
R3×R2 R3)(R2×R4
1×
R+R1 R×4
TD
TD 







I. When T = 10°C, R1 = 3kΩ, RTD(TL) = 1.0385kΩ,
0.93 =
R3×R2 1.03R2)(2.97R3×R4 
When T = 40°C, R1 = 3kΩ, RTD(TU) = 1.154kΩ,
2.79 =
R3×R2 2.89R3)(1.11R2×R4 
II. When T = 10°C, R1 = 1.15kΩ, RTD(TL) = 1.0385kΩ,
1.8 =
R3×R2 1.9R2)(2.1R3×R4 
When T = 40°C, R1 = 1.15kΩ, RTD(TU) = 1.154kΩ,
1.9 =
R3×R2 R3)(R2×R4×2 
2. IC
IC temperature sensor has lower self-heating effect.
We use LM62BIM temperature sensor. The temperature
range is from 10°C to 50°C , corresponding to TL= 0.636V,
and TU= 1.260V. R1=16.4k, C1=4.7uF, R2=100k, R3 =
97.8k, R4 = 19.7k, R5 = 100k. See Figure 11.
+
−
RTH
TMO
4VR
R5
IN+
IC
R2
R1
C1 R4
R3
Figure 11. IC temperature sensor
T
V
TU
TL
V(TU)
V(TL)
Figure 12. Temperature sensor IC characteristics

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
VTMO(TL) = 0.1V, VTMO(TU) = 3.9V
)()(
)()( )()(
LU
LTMOUTMO
OTVTV
TVTV
Vi
V
G





4//35
1
2RR R
R
R
G
2)()( TLTU
IM
VV
V

,
V
VV
VOM 2
21.09.3 


IMIVV 
,
VVOM 2
VI is the output voltage of IC, and VO is the voltage of
TMO pin.
imIN V
RR R
V21 2



,

INRTH VV
453
4R V
RVV RVV ININomIN  



R5=100k, R1=R3//R4, R2=R5.
24 400
4

 GVVG
R
ININ
2
400
3

 GVV
R
ININ
SBDN
SBDN is suggested to be pulled up to VPS with a 10µA
current and contains a 1.50V logic threshold. Drive this
pin to a logic-high to enable the TEC50V20AB. Drive to
a logic-low to disable the TEC controller and enter
micro-power shutdown mode.
ITEC and ILM
When the voltage of the ITEC is VITEC = 2V, the current
of the TEC Controller ITEC=0A. When VITEC = 0V, ITEC
has the maximum reverse current, −20A. When VITEC =
4V, ITEC has the maximum forward current, 20A.
TEC controller is working on the cooling region, when it
has forward current. On the opposite, it works on the
heating region when reversing the current, as shown in
Figure 13.
VITEC
ITEC
4V
2V
0
20A
-20A
Cooling
region
Heating
region
TEC
ITEC
−
+
TEC+
TEC−
Figure 13. VITEC vs. ITEC
ITEC
Maximum TEC current
Allowable
TEC
current
VILM
-20A
20A
2V 4V
Figure 14. VILM vs. ITEC
4VR
R1
R2
S2
2.2uF
ADC
ADC
Control
C1
RILM2
ILM
GND
20k
RILM1
1k
Figure 15. ILM vs. Cooling and Heating Control
The switch S1 is closed @ heating, and open @ cooling

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
Calculate the maximum current in cooling and heating
region according to Figure 15.
1. Cooling region
ITEC≥0A, VILM≥ 2V, Cooling region => S1 = Open;
Maximum cooling current:
ITEC≤
20A×
R2+R1R2
=20A×
4V
VILM
2. Heating region
ITEC < 0A, VILM < 2V, Heating region => S1 = Close;
Maximum heating current:
|ITEC|MAX ≤
20A×
R2//R+R1R2//R
=20A×
4V
V
ILM
ILMILM
3. After deciding the heating current shrinking ratio, we
can determine the value for R1 & R2.
Calculate R1 & R2 ratio
ICOOLMAX =
20A×
R2+R1R1
--------------(1)
Calculate R1 & R2 value by deciding the heating
current shrinking ratio:
KHC = maximum heating current / maximum cooling
current
=
MAX)-(CLITEC-
MAX)-(THITEC-
I
I
--------------(2)
=
R2+R1R2
R2//R+R1R2//R
ILM
ILM
=
R2)+(R1200+R2R1 R2)+(R1200


VTEC and VLM
VTEC = VTEC+ −VTEC−, as shown in Figure 17.
Cooling Range
Heating
Range
Maximum TEC Voltage
Range
Allowable
Output TEC
Voltage
range
VVLM
−50V
50V
2V 4V
VTEC
Figure 16. VTEC vs. VVLM
4VR
R1
R2
S2
2.2uF
ADC
ADC
Control
C1
RVLM
VLM
GND
10k
Figure 17. VLM vs. Cooling and Heating Control
The switch S2 is closed @ heating, and open @ cooling
TMGD
4V
150Ω
TMGD
49.9Ω
Figure 18. TMGD Output Voltage Range

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
The TMGD pin outputs the maximum source current
and sink current of 20mA. The output current will cause
voltage drop, see Figure 18.
VLM and ILM
If you want to use this TEC controller for other
applications not discussed here, such as with wave locker
controllers, consult with us. The same for other
customizations, such as setting the ILM and VLM by
using voltage source swings above 4V and/or VPS.
An external voltage connects the ILM pin through a
resistor. This voltage can be used to adjust the voltage
range of cooling or heating, and advice is 1.5V. The
resistor can be used to adjust the difference of cooling
and heating, and advice is 10kΩ. See Figure 19.
For example, the voltage midpoint of the ILM pin (Vm)
is 2V. Adjust the external voltage, and make the voltage
range 1V, but it is only with the center of 2V (Vm). If you
adjust the resistor W2, you can move the limit of the
cooling to be greater than the limit of the heating. It is
shown in Figure 20 and Figure 21.
W1
4VR
S1
2.2uF
ADC
ADC
Control
+
−W2
20k
10k
C1
RILM
10k
Figure 19. ILM vs. Cooling and Heating Control 2
1.4V
2V
1.3V
2.5V
2.7V
0.5V 0.6V 0.7V
0.5V 0.6V 0.7V
1.5V
2.6V
Figure 20. Adjust the External Voltage
1.6V
2V
1.5V
2.3V
2.5V
0.7V 0.6V 0.5V
0.3V 0.4V 0.5V
1.7V
2.4V
1.3V
1.4V
2.6V
2.7V
Figure 21. Adjust the Resistor
VLM/ILM
(V)
T(ms)
Heating
Cooling
Control
Control
Figure 22. The Waveform on the VLM or ILM Pin
@ SB State
Cooling
Heating
Control
Control
VLM/ILM
(V)
T(ms)
Figure 23. The Waveform on the VLM or ILM Pin
@ Operation State

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Analog Technologies
TEC50V20A
High Voltage High Current TEC Controller
We can tell the VLM or ILM voltage in cooling control
or heating control through the waveforms on the VLM or
ILM pin, see Figure 22 and Figure 23. The duty cycle in
Figure 22 is 99% and 1% in Figure 24. We can also
measure both voltages by a multimeter. When the
controller is in the Standby State, the voltage measured
by the multimeter is the VLM or ILM voltage in cooling
control. When the controller is in Operation State, the
voltage measured by the multimeter is the VLM or ILM
voltage in heating control.
Temperature Network
TEC50V20AB comes with a customized internal
compensational network for which the component values
are specified by the customer. See Figure 7.
TEC50V20AB comes with a customized Temperature
network. See Figure 7 and Figure 8.
The resistors and capacitors controlled by the dial switch
are used to adjust the compensation network. The default
values of resistors and capacitors are shown in Table 4
Table 4. Pin Function Descriptions
Parameter
Value
Note
RP
10MΩ
RI
2MΩ
RD
24.9kΩ
CI
100nF
CD
1μF
Table 5 is printed on the actual TEC50V20AB, which
shows the values of VSBDN.
GETTING STARTED
Hook up the power supply, TEC and thermistor. There
are 2 solder pads in the upper right area on the edge for
connecting the DC power supply voltages. The
connection can be done by clipping or soldering on the
pads. Usually the power supply is set from 12V to 50V, a
power supply of about having higher voltage than the
maximum output voltage. There are also 2 solder pads in
the upper right area on the edge for connecting the TEC
terminals in the right polarity as indicated onto the board.
Connect the thermistor terminals to the board, there is no
polarity requirement. On the top of the board, there is the
switch bank S1, which is used for adjusting D1, D2 and
D3 to achieve different functions, in Table 5. At the same
time, adjust the position of S2 with S1. There is an IC
port on the bottom left of the edge for IC temperature
sensor input. The switch of S3 is used to adjust the
compensation network of temperature control loop by
inputting a square wave disturbing signal in temperature
input point, which enables the system to generate
corresponding response waveform. At this time, observe
the waveform change by oscilloscope, and adjust and
optimize the compensation network of the temperature
control loop so as to achieve the best waveform at the
same time. Response waveform is achieved by
measuring IDR with oscilloscope, as shown in Figure 24
and Figure 25. The compensation network components
consist of RI, RD, RP, CD and CI, which will be adjusted
by S4, S5, S6, S7 and S8. These connections can be done
by clipping or soldering on the pads. Check the
evaluation board connections, making sure that they are
all correctly connected.
Figure 24. Rise Waveforms of IDR
Figure 25. Fall Waveforms of IDR
ON=1
D1
D2
D3
VSBDN
0
0
0
0V
OFF
0
0
1
1.8V
SB
OFF=0
0
1
0
2.2V
IC
1
0
0
2.6V
RTD
1
1
1
3.6V
RTH
Best
Slow
Overshooting
Slow
Best
Overshooting

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Analog Technologies
TEC50V20AB
High Voltage High Current TEC Controller
1. Turn on and off the controller. This can be done by either
turning off the power supply or turning off the shut-
down pin of the controller. To do the latter, turn off the
switch D1, D2, D3 in S1 to power off the controller.
2. Check the voltage reference. Use a voltmeter to check
the voltage reference pin SNCO having an accurate
4.096V.
Tune the compensation network. The purpose for this step is
to match the controller compensation network with the
thermal load characteristics thus that the response time and
temperature tracking error are minimized. Adjust the
potentiometer W1 to change the set-point temperature TMS
just a small amount, simulating a step function, or press S3
to simulate a step function. At the same time, connect an
oscilloscope at the IDR test pin (on the left side of the
evaluation board), set it to a scrolling mode (0.2
Second/Division or slower) and monitor the waveform of
IDR as TMS is fed by a step function signal. The circuit in
the compensation network is shown in Figure 26 below.
Figure 26. Compensation Network
H()
Gp

Gd
1
3
2
4
1.41Gp
0.71Gd
Figure 27. Transfer Function of the Compensation Network
The transfer function of the compensation network, defined
as H()=IDR()/TMS(), is shown in Figure 27.
In principle, these are the impacts of the components to the
tuning results:
a. RP/RIdetermines the gain for the proportional
component of the feedback signal which is from the
thermistor, Gp = RP/RI, in the control loop, the higher
the gain, the smaller the short term error in the target
temperature (which is of the cold side of the TEC)
compared with the set-point temperature, but the higher
the tendency of the loop’s instability.
b. RP/RDdetermines the gain for the differential
component, Gd = RP/(RD//RI) RP/RD, where symbol
“//” stands for two resistors in parallel, since RI>> RD,
RD//RIRD. The higher the gain, the shorter the rise
time of the response, the more the overshoot and/or the
undershoot will be.
c. CI×R Pdetermines the corner frequency, 1= 1/(CI×R P),
where the integral component starts picking up, as the
frequency goes down. It determines the cut-off
frequency below which the TEC controller will start
having a large open loop gain. The higher the open loop
gain, the smaller the tracking error will be.
d. CD×R Idetermines the corner frequency, 2=1/(CD×R I),
where the differential component starts picking up (see
Figure 27), as the frequency goes up.
e. CD×R Ddetermines the corner frequency, 3=1/(CD×R D),
where the differential component starts getting flat. It
determines the cut-off frequency above which the TEC
controller will give extra weight or gain in response.
f. 1nF×R Pdetermines the corner frequency,
4=1/(1nF×R P), where the differential component
starts rolling down. Since this frequency is way higher
than being needed for controlling the TEC, 4 does not
need to be tuned. The capacitor is built into the TEC
controller module, not the evaluation board.
To start the tuning, turn off the differential circuit by setting
CDOpen. Turn W1 quickly by a small angle, back and forth,
approximately 5 seconds per change. Set CIto 1uF, set RIto
1M, and increase the ratio of RP/RIas much as possible,
provided the loop is stable, i.e. there are no oscillations seen
in IDR. Then, minimize CIas much as possible, provided the
loop is stable. The next step is to minimize Rd and maximize
CDwhile maintaining about 10% overshoot found in IDR.
Optimum result can be obtained after diligent and patient
tuning. The tuning is fun and important.
When the TEC controller is used for driving a TEC to
stabilize the temperature of a diode laser, there is no need to
turn on the laser diode while tuning the TEC controller. To
simulate the active thermal load given by the laser diode,
setting the set-point temperature lower than the room
temperature is enough.
For a typical laser head used in EDFA’s or laser transmitters
(found in DWDM applications, for instance), RI= 1M,
RP= 1M, CI= 470nF, CD= 2.2F, and RD= 200k. These
values may vary, depending on the characteristics of a
particular thermal load.
To be conservative in stability, use larger CIand larger RI; to
have quicker response, use smaller Rd and larger CD.
The closer to the TEC the thermistor is mounted, the easier

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Analog Technologies
TEC50V20AB
High Voltage High Current TEC Controller
to have the loop stabilized; the shorter the rise time, the
settling time of the response will be.
1. After tuning, the values of the capacitors for CDand CI
can be read off the capacitor selection switches. The
values of the resistors, RI, Rd and RP, can be measured
by an Ohm-meter by connecting to the resistor pins. RI
can be read off between TMS and CMIN test points; RD
can be read off between CMIN and CDRD test points;
RPcan be read off between CMIN and CIRP test points;
CDcan be read off between TMS and CDRD test points;
CIcan be read off between CIRP and IDR test points.
2. After the compensation network is tuned properly, we
can now adjust set-point temperature to see if the TEC
controller can drive the target temperature to a certain
range and with high stability. Turn the temperature set-
point TMS potentiometer W1 while monitoring its
output voltage at TMS test point (2nd row on left side of
the board), watch the LED: when it turns to green, the
target temperature is locked to the set-point temperature
within 0.1C or less. The relationship between the set-
point voltage vs. the set-point temperature is given in the
datasheet. After seeing the LED lock into the set-point
temperature, IDR should be a constant voltage as shown
in the oscilloscope and the voltage between TMS and
TMO should be very small, less than 10mV. When a
standard TEC controller is used, the 10mV represent a
0.07temperature error.
3. Set output voltage limit. Adjust the potentiometer W4 to
set the voltage limit. TP VLIM is the test point for W4.
After the VLM is tuned properly, adjust W5 to achieve
different voltage limit for heating and cooling. TP
VLIMO is the test point for W5. As is shown in Figure
28 and Figure 29.
4. Set output current limit. Adjust the potentiometer W2 to
set the current limit. TP ILIM is the test point for W2.
After the current limit is tuned properly, adjust W3 to
achieve different ILM for heating and cooling. TP
ILIMO is the test point for W3. As is shown in Figure 28
and Figure 29.
The schematic is shown in Figure 30 below.
1.4V
2V
1.3V
2.5V
2.7V
0.5V 0.6V 0.7V
0.5V 0.6V 0.7V
1.5V
2.6V
Figure 28. Adjust W2 or W4
1.6V
2V
1.5V
2.3V
2.5V
0.7V 0.6V 0.5V
0.3V 0.4V 0.5V
1.7V
2.4V
1.3V
1.4V
2.6V
2.7V
Figure 29.Adjust W3 or W5

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Analog Technologies
TEC50V20AB
High Voltage High Current TEC Controller
Figure 30. Schematic of Setting Output Voltage or Current Limit
Figure 31. Schematic of TEC50V20AB

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Analog Technologies
TEC50V20AB
High Voltage High Current TEC Controller
TYPICAL CHARACTERISTICS
Table 6. Measurement Data of Rth vs. Temperature
Temp.
(°C )
Rth
(kΩ)
TMO
(V)
Ideal
Linear
(V)
Error
Temp.
(°C )
Rth
(kΩ)
TMO
(V)
Ideal
Linear
(V)
Error
15
15.7049
0.05
0.1
−0.05
26
9.5718
2.23
2.25
−0.02
16
14.9944
0.24
0.3
−0.06
27
9.1642
2.44
2.44
0
17
14.3198
0.43
0.49
−0.06
28
8.776
2.64
2.64
0
18
13.6792
0.63
0.69
−0.06
29
8.4063
2.85
2.83
0.02
19
13.0705
0.82
0.88
−0.06
30
8.0541
3.05
3.03
0.02
20
12.4922
1.02
1.08
−0.06
31
7.7184
3.25
3.22
0.03
21
11.9425
1.22
1.27
−0.05
32
7.3985
3.46
3.42
0.04
22
11.4198
1.42
1.47
−0.05
33
7.0935
3.66
3.61
0.05
23
10.9227
1.62
1.66
−0.04
34
7.0935
3.86
3.81
0.05
24
10.4499
1.82
1.86
−0.04
35
6.5251
4.06
4.00
0.06
25
10
2.03
2.05
−0.02
Figure 32. TMO Pin Voltage vs. Set-point Temperature