210kW

T

SET

OUT

V+

HYST

SET

V

TEMP

TMP300

3 A

m

Proportional

toT

A

AnalogOut

OPA335

-

50

-

25

0

1.00

0.75

0.50

0.25

0

-

0.25

-

0.50

-

0.75

-

1.00

25

50

75

100

125

Temperature( C)

°

210kW

T

SET

OUT

V+

HYST

SET

V

TEMP

TMP300

3 A

m

Proportional

toT

A

Open-DrainControl

Voltagesource

totesttrippoint.

DAC8560

TMP300

www.ti.com

SBOS335C – JUNE 2005 – REVISED JANUARY 2011

ANALOG TEMPERATURE OUTPUT

USING A DAC TO SET THE TRIP POINT

The trip point is easily converted by changing the

(210k

Ω). Avoid loading this pin to prevent degrading

digital-to-analog

converter

(DAC)

code.

This

the analog out value or trip point. Buffer the output of

technique can be useful for control loops where a

this pin when using it for direct thermal measurement.

large thermal mass is being brought up to the set

Figure 9 shows buffering of the analog output signal.

temperature and the OUT pin is used to control the

heating element. The analog output can be monitored

in a control algorithm that adjusts the set temperature

to prevent overshoot. Trip set voltage error versus

temperature is shown in Figure 10, which shows error

in °C of the comparator input over temperature. An

alternative method of setting the trip point by using a

DAC is shown in Figure 11.

Figure 9. Buffering the Analog Output Signal

Figure 10. Trip Set Voltage Error vs Temperature

Copyright © 2005–2011, Texas Instruments Incorporated

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