TMP007 datasheet(45/55 Pages) TI1

45 / 55 page

Field of View

Target Object

PCB Copper Ground

Empty FR-4 Material

TMP007

IR Sensor

SENSOR_PCB

TMP007

Electrically

Connected

Thermally

Isolated

BOARD

TMP007

www.ti.com

SBOS685C – APRIL 2014 – REVISED JULY 2015

Product Folder Links: TMP007

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10 Layout

10.1 Layout Guidelines

The IR thermopile sensor in the TMP007 is as susceptible to conducted and radiant IR energy from below the

sensor on the PCB as it is to the IR energy from objects in its forward-looking field of view. When the area of

PCB below the TMP007 is at the same temperature as the die or substrate of the TMP007, heat is not

transferred between the IR sensor and the PCB. However, temperature changes on a closely-placed target

object or other events that lead to changes in system temperature can cause the PCB temperature and the

TMP007 temperature to drift apart from each other. This drift in temperatures can cause a heat transfer between

the IR sensor and the PCB to occur. Because of the small distance between the PCB and the bottom of the

sensor, this heat energy will be conducted (as opposed to radiated) through the thin layer of air between the IR

sensor and the PCB below it. This heat conduction causes offsets in the IR sensor voltage readings and

ultimately leads to temperature calculation errors. To prevent and minimize these errors, the TMP007 layout

must address critical factors:

Thermally isolate the TMP007 from the rest of the PCB and any heat sources on it. Provide a stable thermal

environment to reduce the noise in the measurement readings

Figure 60 illustrates the concept of thermally isolating the TMP007 from the PCB and external heat sources such

as other components, air currents, and so on.

Figure 60. Principle of TMP007 Thermal Isolation

TMP007 Datasheet(PDF) 45 Page - Texas Instruments