REV. B

–5–

TMP12

SUPPLY VOLTAGE (V)

500

0

450

400

350

300

250

200

150

100

50

0

12345678

NO LOAD

HEATER OFF

TPC 10. Supply Current vs. Supply

Voltage

TEMPERATURE ( C)

0.5

–75

0.4

0.3

0.2

0.1

0

–25

25

75

125

175

V+ = 4.5V TO 5.5V

NO LOAD

HEATER OFF

TPC 11. VPTAT Power Supply

Rejection vs. Temperature

TEMPERATURE ( C)

40

–75

36

32

28

24

20

–25

25

75

125

175

38

34

30

26

22

V+ = 5V

TPC 12. Open-Collector Output Sink

Current vs. Temperature

APPLICATIONS INFORMATION

A typical application for the TMP12 is shown in Figure 2. The

TMP12 package is placed in the same cooling airflow as a high

power dissipation IC. The TMP12’s internal resistor produces a

temperature rise that is proportional to air flow, as shown in

Figure 3. Any interruption in the air flow will produce an addi-

tional temperature rise. When the TMP12 chip temperature

exceeds a user-defined setpoint limit, the system controller can

take corrective action, such as reducing clock frequency, shutting

down unneeded peripherals, turning on additional fan cooling,

or shutting down the system.

PGA

PACKAGE

PGA

SOCKET

POWER IC

AIR FLOW

PC BOARD

TMP12

Figure 2. Typical Application

TEMPERATURE ( C)

700

–75

500

300

100

–25

25

75

125

175

600

400

200

0

LOAD = 10mA

LOAD = 5mA

LOAD = 1mA

TPC 13. Open-Collector Voltage vs.

Temperature

65

60

35

0

250

50

100

150

200

55

50

45

40

A

B

C

D

E

A. TMP12 DIE TEMP NO AIR FLOW

B. HIGH SETPOINT

C. LOW SETPOINT

D. TMP12 DIE TEMP MAX AIR FLOW

E. SYSTEM AMBIENT TEMPERATURE

Figure 3. Choosing Temperature Setpoints

Temperature Hysteresis

The temperature hysteresis at each setpoint is the number of

degrees beyond the original setpoint temperature that must be

sensed by the TMP12 before the setpoint comparator will be

reset and the output disabled. Hysteresis prevents chatter and

motorboating in feedback control systems. For monitoring tem-

perature in computer systems, hysteresis prevents multiple

interrupts to the CPU which can reduce system performance.