TMP007 datasheet(44/55 Pages) TI

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OBJ

30 nW

140 mK

213 nW/K

OUT

OBJ B OBJ

det

OBJ

NEP

1 cos

213

rms noise

OBJ

OUT

Sensor

0.25 9

110 mK

2 3 9.

SENSOR

OBJ

2 3

cos

OUT

OBJ B OBJ

det

OBJ

cos

0 800

TMP007

SBOS685C – APRIL 2014 – REVISED JULY 2015

www.ti.com

The value of cos

θ is shown in Equation 21:

where

•

r is the distance between the detector and the object (10 mm).

•

D is the diameter of the object (15 mm).

(21)

Differentiating with respect to object temperature, a small change in temperature creates a small change in the

measured voltage given by Equation 22:

(22)

Substituting values for the parameters yields Equation 23:

(23)

Based on Figure 4, the sensor rms noise at TDIE = 25°C is ~0.25 µV; thus, the rms variation in temperature

measurement is as shown in Equation 24:

(24)

The peak-to-peak noise is approximately six times the rms noise; therefore, estimate an accuracy of

approximately ±0.33°C.

This estimate can also be made using the noise-equivalent power (NEP), noting that NEP is the ratio of noise to

responsivity, as shown in Equation 25:

(25)

Assuming the system is sensor-noise limited, then from Figure 5, the NEP is ~30 nW at 25°C, as shown in

Equation 26:

(26)

Again, the peak-to-peak noise is approximately 6X the rms noise; therefore estimate an accuracy of

approximately ±0.42°C.

The different results from these two techniques is because of estimated values used for some parameters. The

purpose of these techniques is not to obtain exact answers, but rather to quickly estimate the feasibility of a

system implementation based on basic system parameters. These examples are intended only as guidelines; the

specific values for the parameters depend on the specific system details.

9 Power-Supply Recommendations

The TMP007 is designed to operate with a power supply voltage (VS) of between 2.5 V and 5.5 V. This input

supply must be well regulated. The die temperature measurement (TDIE) dependence on supply voltage is

typically 20 m°C/V for TDIE > 0°C (see Figure 9). The power-on reset (POR) has a nominal value of 1.9 V at TDIE

= 25°C. The POR increases with decreasing die temperature (see Figure 12). Place the decoupling capacitor

(0.1 µF recommended) as close as possible to the device without obstructing the field of view.

As an aid to designing the power supply and estimating power and energy requirements, a number of typical

curves are supplied. The typical characteristics for supply current vs TDIE (Continuous Conversion) are given in

Figure 15. Typical values for shutdown current as a function of TDIE and supply voltage are given in Figure 14.

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