Remote Diode Temperature (GC)

-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

Mean6$

Mean + 6$

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

TMP451

SBOS686A – JUNE 2013 – REVISED DECEMBER 2014

www.ti.com

Typical Application (continued)

Figure 44. Temperature Step Response

Figure 43. TMP451 Remote Diode Temperature Drift

(Diode-Connected 2N3906)

9 Power Supply Recommendations

The TMP451 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 device measures very small voltages using very low currents;

therefore, noise at the device inputs must be minimized. Most applications using the TMP451 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 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 45. 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 0.1

μF local bypass capacitor directly between the V+ and GND of the TMP451 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

device.

5. If the connection between the remote temperature sensor and the TMP451 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 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 device to avoid

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

32

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