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LMT70A: Suggestion for temeperature monitoring wearable band

Part Number: LMT70A
Other Parts Discussed in Thread: LMT70, TMP117

Hi Team 

We are making  a wearable  band withing the range of  +-0.1 degree centigrade to  measure  body  temperature by sensing temperature  on wrist.

1) Does  TI has  any design for  same/ Similar  application?

2) Please  suggest which part we should  proceed as we  have to make very cheap band 

3) We are thinking of mounting a metal part/ thick pogo pin on bottom side  PCB in such a manner that  it come out  of  mechanical surface and tough skin. Do you have any suggestion for such part ? Does  TI used any such part off the shelf  part in there  internal testing while  making probe  of  any  wearable  heart  rate  monitor/ECG, if  so please suggest part  no 

4) while  going through  http://www.ti.com/lit/an/snia021b/snia021b.pdf on page  no  4 it is  mentioned that "Better results can be obtained if underfill material is added surrounding the LMT70 die (package) as shown in Figure 4." Can you please  tell any example of  material which can be used  ?

5) We have one  concern that suppose  user didn't tied his wearable we  may not able to measure temp  properly . Do you have any suggestion how  we  can give  notification that probe not properly touching hand ?

we  are  thinking of proximity sensor( not sure  about sensitivity)  and SPO2 sensor  (disadvantage is high  current consumption and cost ).

6) How sweat under the probe can impact temperature  measurement. Consider use case  person is in 40 degree  ambient and  we  need  to measure  temperature  every 30 min.

  • Hi Abhishek,

    Below is my feedback.

    1) Does TI has any design for same/ Similar application?

    Please see this FAQ for design information on this topic. e2e.ti.com/.../895494

    2) Please suggest which part we should proceed as we have to make very cheap band

    For 0.1 °C applications I would suggest either TMP117 or LMT70.

    3) We are thinking of mounting a metal part/ thick pogo pin on bottom side PCB in such a manner that it come out of mechanical surface and tough skin. Do you have any suggestion for such part ? Does TI used any such part off the shelf part in there internal testing while making probe of any wearable heart rate monitor/ECG, if so please suggest part no

    Please see these reference designs for reference:    

    4) while going through www.ti.com/.../snia021b.pdf on page no 4 it is mentioned that "Better results can be obtained if underfill material is added surrounding the LMT70 die (package) as shown in Figure 4." Can you please tell any example of material which can be used ?

    Let me check to see what underfill material was used in that app note.

    5) We have one concern that suppose user didn't tied his wearable we may not able to measure temp properly . Do you have any suggestion how we can give notification that probe not properly touching hand ?

    we are thinking of proximity sensor( not sure about sensitivity) and SPO2 sensor (disadvantage is high current consumption and cost ).

    You could try using TI CapTIvate technologies for low power contact detection: 6) How sweat under the probe can impact temperature measurement. Consider use case person is in 40 degree ambient and we need to measure temperature every 30 min.

    Sweat will have a different thermal conductivity than your skin, but as long as there is a good thermal path from the wrist to the temperature sensor and the temperature sensor is not exposed to sweat directly there shouldn't be any concerns.

  • Hi Abhishek,

    As for the underfill, E1216M is a common underfill material that is used in assembly houses.

    Thanks,

    David