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10 • 400 Hot Springs Road, Carson City NV 89706 • (775) 883-0820 • Fax (775) 883-0827 • www.hytek.com

HY5600B

TEC Controller Evaluation Board

Figure 1

Procedure for Setting Up the

HY5600 Evaluation Board

1. Connect a Thermoelectric Cooler and a

Thermistor to the evaluation board as shown in

the schematic diagram. A phone jack along

with interconnect cables are provided for

interfacing the Evaluation Board to the Ther-

moelectric Cooler and Thermistor.

2. Select a Temperature set resistor (R

) that will

program the HY5600 to regulate the TEC to

the desired temperature. For example: A

56K

Ω

resistor will set the TEC to a tempera-

ture of –10°C if Dale 1M1002, 10K

Ω

thermistor

is used. See the "Set Temperature vs. Pro-

gram Resistor (R

)" curve in HY5600 Data

Sheet to determine the correct value of R

for

your application.

Caution: The HY5600

controller will supply maximum programmed

cooling current to the TEC if R

is not present.

The thermoelectric cooler could be damaged if

this condition exists for a prolonged period of

time.

3. A 1 µF capacitor and a 6.8M

Ω

resistor have

been selected for the loop stabilization

components C

and R

. These values will

more than likely be satisfactory for most

applications. They can easily be changed if

they are not. (Reference the HY5600 Data

Sheet.)

4. There is a position for R

, the loop gain

control resistor, on the evaluation board.

However, this resistor has been omitted. This

is because there is 10M

Ω

resistor internal to

the HY5600 that is in parallel with R

that

will, in most cases, provide sufficient loop

gain.

Thermoelectric Cooler Controller Evaluation Board

TEC

Controllers

Laser

iode

Drivers

Micro-heaters

The HY5600 Evaluation Board

is a printed

circuit board containing the HY5600 TEC Controller

plus other components required to make an evalua-

tion temperature controller for Thermoelectric Cool-

ers. This evaluation board provides the means to

quickly interface the HY5600 with a Thermoelectric

Cooler and to evaluate performance before designing

a printed circuit board. A schematic diagram for the

test board is shown. The evaluation board contains

loop compensation components of 1µF and 6.8 M

Ω

and R

). These components can easily be re-

placed if it is found that other values are more suit-

able. Terminals for the temperature set resistor (R

)

are provided on the Evaluation Board for the user to

set the desired TEC temperature.

400 Hot Springs Road, Carson City NV 89706 • (775) 883-0820 • Fax (775) 883-0827 • www.hytek.com • 11

HY5600B

TEC Controller Evaluation Board

5. Connect the V

and V

power supplies to the test

board. The desired values for these supplies should be

set before the power supplies are connected to the

evaluation board. Note that V

should be able to supply

more than 2 Amperes of current. Before turning off the

power supplies, make certain the TEC, the Thermistor

and the temperature set resistor (R

) are connected to

the Evaluation Board. In addition, SW1 should be in the

“off” position.

6. Turn on the power supplies. Maximum current will flow

through the TEC as long as the temperature set resistor

is greater than the resistance of the Thermistor. The

HY5600 will continue to supply maximum cooling current

until the resistance of the Thermistor increases to a value

equal the R

. The current supplied by the HY5600 will

Procedure for Setting Up the HY5600 Evaluation Board

(continued)

then decrease to a value required to maintain the TEC at

the set temperature.

7. Potentiometer R

controls the maximum current that the

HY5600 can supply to the TEC. The Evaluation Board

has been adjusted at the factory so that a maximum of

0.8 Amperes flows through the Thermoelectric Cooler. If a

higher or lower value of cooling current is desired, push

Switch #1 to the “on” position. This action will force the

HY5600 to supply maximum cooling current to the TEC.

This maximum cooling current can be adjusted to the

desired value with the potentiometer labeled R

. Do not

exceed the maximum current specification for the TEC.

Return SW1 to the “off” position for normal operation.

Figure 2

12 • 400 Hot Springs Road, Carson City NV 89706 • (775) 883-0820 • Fax (775) 883-0827 • www.hytek.com

HY5600B

TEC Controller Evaluation Board

The output of the temperature measuring circuit of the

HY5600 is Pin 4. Test Point 4 on the evaluation board corre-

sponds to this output. The temperature measurement circuit

of the HY5600 is illustrated in Figure 3 where R

is the ther-

mistor that measures the temperature of the Thermoelectric

Cooler and R

is the temperature set resistor. The output

voltage (E

) at Test Point 4 is given by the equation below.

This output feeds the integrator portion of the HY5600 which

in turn applies power to the TEC. Cooling of the TEC results

The temperature controlling stability of the HY5600 vs. Ther-

moelectric Cooler (TEC) drive current is measured using the

test setup illustrated in Figure 4. The thermoelectric cooler

and temperature sensing thermistor are placed in a tem-

perature chamber. An identical thermistor is mounted in inti-

mate contact with the sensing thermistor. Both thermistors

are embedded in an aluminum block that is attached to the

top surface of the TEC. The bottom face of the TEC is at-

tached to a heat sink. The temperature of the controlling

Measuring the Temperature Regulating Performance of the HY5600

until R

equals R

. This produces a voltage (E

) of 2.500

Volts between TP 4 and signal ground. The Voltage/Tem-

perature coefficient at TP 4 is approximately 50 mVolts per

°C when this occurs. Monitoring Test Point 4 will tell the

user when the loop is stabilized and how accurately the

temperature is controlled. When the loop has stabilized, the

voltage at TP 4 will be stable to better than 1 mVolt. This

equates to a temperature stability of better than .02 °C.

Figure 3

thermistor is set to approximately 25°C by selecting an R

value of 10K

Ω

. R

is a precision temperature stable resistor.

TEC drive current is monitored as the Temperature of the

chamber is increased above 25°C. Resistance of the sec-

ond thermistor is recorded and converted to temperature for

various TEC drive currents. A typical plot of Temperature

stability vs. TEC Drive Current is shown in Figure 6.

Figure 4

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The temperature controlling stability of the HY5600 vs. Base

Temperature* is measured using the test setup illustrated in

Figure 5. The HY5600 is placed inside the temperature

chamber. The thermoelectric cooler / thermistor assembly

is placed outside the chamber. In addition, the 13K

Ω

tem-

perature set resistor R

is located outside the chamber to

eliminate any temperature effects due to this resistor. This

* Base Temperature is the temperature of the aluminum

heat spreader (Base) of the HY5600. In the experiment il-

lustrated in Figure 5, the programmed temperature to the

TEC assembly and its ambient temperature are almost

equal. The TEC current is therefore almost zero amperes

thus eliminating any self heating effects in the HY5600. In

HY5600B

TEC Controller Evaluation Board

value of R

sets the temperature of the controlling ther-

mistor to approximately 18°C. The temperature of the test

chamber is varied from –55°C to +110°C. Resistance of the

temperature measuring thermistor is recorded and con-

verted to temperature. A typical plot of Temperature stability

vs. Base temperature of the HY5600 is shown in Figure 7.

this case, the temperature of the HY5600 is virtually equal

to the temperature of the chamber. In practice, the tem-

perature of the base of the HY5600 is a function of the TEC

drive current, the HY5600 heat sink size, the air flow

across the heat sink and the temperature of the surround-

ing air.

Figure 5

Figure 6

Figure 7