INA330

9

SBOS260

www.ti.com

FIGURE 6. PID Temperature Control Loop.

25

°C. V

ADJ = 2.5V + 0.9V will change the set-point by 1°C.

A 0V to 5V D/A converter will provide approximately

±2.5°C

adjustment range. A 12-bit D/A converter will allow for

approximately 0.001

°C resolution on the set-point tempera-

ture.

For best temperature stability, the set-point temperature

voltage should be derived ratiometrically from VBIAS. A D/A

converter used to derive the set-point voltage should share

the same reference voltage source as VBIAS. Likewise, the 1V

INA330

+5V(2)

V

2

1V(1)

V

1

2

3

10

1

4

Enable

+5V

I

1

I

2

R

SET

10k

Ω

R

G

200k

Ω

Thermistor

R

SET = 10kΩ

C

FILTER

500pF

I

O = I1 – I2

V

O

8

7

V

ADJUST = 0V to 5V

= 2.5V at 25

°C Set-Point

D/A

Converter

Temperature

Adjust

V

REF

(1) = +5V

R

1

R

3

R

2

OPA348

C

1

C

3

+5V

R

4

10k

Ω

10k

Ω

10k

Ω

OPA569

OPA569

TEC

Cooling

C

2

PID

3.3V

3.3V

10k

Ω

10k

Ω

NOTES: (1) Ratiometrically derived voltages.

(2) The INA330 can also use a 3.3V, supply;

however, components must be chosen appropriate

to the smaller output voltage range.

✻

indicates direction of voltage change for

rising temperature at the thermistor.

TEC DRIVER AMPLIFIER OPTIONS

OPA569

2A Linear Amplifier

DRV591

3A PWM Power Driver

DRV593

3A PWM Power Driver

DRV594

3A PWM Power Driver

4k

Ω

1k

Ω

V

REF

(1)

+5V

10k

Ω

10k

Ω

V

REF

(1)

+5V

95

6

V

BIAS

(1)

2.5V

+

–

✻

✻

✻

✻

source for V1 and V2 should be derived from the same

reference.

The PID loop compensation can be optimized for loop

stability and best response to thermal transients by adjusting

C1, C2, C3, R2, R3, and R4. This is highly dependant on the

thermal characteristics of the temperature-controlled block

and thermistor/TEC mounting. Figure 7 shows a circuit that

can be used as an intermediate circuit to easily adjust

components and determine system requirements.

FIGURE 7. Diagnostic and Optimization PID Temperature Control Loop.

C

2

1

µF

R

7

10M

Ω

R

6

5k

Ω

INA330

+5V

+1V

Enable

+5V

R

SET

10k

Ω

R

G

200k

Ω

Thermistor

R

THERM = 10kΩ

C

FILTER

500pF

V

ADJ

D/A

Converter

Ref

R

4

10k

Ω

R

2

200

Ω

R

1

2k

Ω

V

BIAS

1/4

OPA340

R

3

10k

Ω

C

1

22nF

R

8

10k

Ω

1/4

OPA4340

R

10

100k

Ω

R

11

10k

Ω

1/4

OPA4340

R

9

100k

Ω

C

3

1

µF

V

BIAS

V

BIAS

V

BIAS

R

13

1M

Ω

R

14

10k

Ω

1/4

OPA4340

R

12

100k

Ω

Differentiator

TC: 100ms to 1s

Integrator

TC: 1s to 10s

C

4

0.1

µF

Power

Amplifier

OPA569

DRV591

DRV593

DRV594

To

TEC

1/2

OPA2340

R

15

10k

Ω

Proportional

V

BIAS

R

5

5k

Ω

V

1

V

2

3

2

1

10

75

6

8

7

4

I

1

I

2

This versatile PID compensation circuit allows

independent adjustment of the Proportional,

Integral, and Derivative control signals to

facilitate optimization of loop dynamics. The

results can then be duplicated using the circuit

shown in Figure 6.