Remote Diode Temperature (qC)

-40

-25

-10

5

20

35

50

65

80

95

110 125

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

D001

Mean

Mean

66

Mean + 66

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

±1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Time (s)

C007

25

TMP451-Q1

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SLOS877B – OCTOBER 2014 – REVISED JUNE 2019

Product Folder Links: TMP451-Q1

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Typical Application (continued)

Figure 20. TMP451-Q1 Remote Diode Temperature Drift

(Diode-Connected 2N3906)

Figure 21. Temperature Step Response

9 Power Supply Recommendations

The TMP451-Q1 device operates with a power supply range of 1.7 V to 3.6 V. The device is optimized for

operation at 3.3-V supply but can measure temperature accurately in the full supply range.

A power-supply bypass capacitor is recommended. Place this capacitor as close as possible to the supply and

ground pins of the device. A typical value for this supply bypass capacitor is 0.1 μF. Applications with noisy or

high-impedance power supplies may require additional decoupling capacitors to reject power-supply noise.

10 Layout

10.1 Layout Guidelines

Remote temperature sensing on the TMP451-Q1 device measures very small voltages using very low currents;

therefore, noise at the device inputs must be minimized. Most applications using the TMP451-Q1 have high

digital content, with several clocks and logic level transitions creating a noisy environment. Layout should adhere

to the following guidelines:

1. Place the TMP451-Q1 device as close to the remote junction sensor as possible.

2. Route the D+ and D– traces next to each other and shield them from adjacent signals through the use of

ground guard traces; see Figure 22. If a multilayer PCB is used, bury these traces between ground or V+

planes to shield them from extrinsic noise sources. 5 mil (0.127 mm) PCB traces are recommended.

3. Minimize additional thermocouple junctions caused by copper-to-solder connections. If these junctions are

used, make the same number and approximate locations of copper-to-solder connections in both the D+ and

D– connections to cancel any thermocouple effects.

4. Use a 0.1μF local bypass capacitor directly between the V+ and GND of the TMP451-Q1 device. For

optimum measurement performance, minimize filter capacitance between D+ and D– to 1000 pF or less .

This capacitance includes any cable capacitance between the remote temperature sensor and the TMP451-

Q1 device.

5. If the connection between the remote temperature sensor and the TMP451-Q1 device is less than 8-in (20,32

cm) long, use a twisted-wire pair connection. For lengths greater than 8 in, use a twisted, shielded pair with

the shield grounded as close to the TMP451-Q1 device as possible. Leave the remote sensor connection

end of the shield wire open to avoid ground loops and 60-Hz pickup.

6. Thoroughly clean and remove all flux residue in and around the pins of the TMP451-Q1 device to avoid

temperature offset readings as a result of leakage paths between D+ and GND, or between D+ and V+.