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TMP112D: About Temp sensor application

Jimmy WANG
Genius 3635 points
Part Number: TMP112D
Other Parts Discussed in Thread: TCA9548A, TMP112, TMP275

Tool/software:

Hi team,

The customer wants to use a temperature sensor to detect the temperature of the air blown out by the fan.

Do you recommend using TMP112D for this design? BTW if want to use 8 devices how to define address? thanks 

  • 0
    Genius 3635 points

    Hi team,

    If the customer does not want to use the DIP switch to assign the device address.
    Are there other methods you can recommend? Similar to TCA9548A
    Or there are new temperature sensors that have this function. 

  • 0 in reply to Jimmy WANG
    TI__Intellectual 2405 points

    Hi Jimmy,

    You can use the TMP112D to measure air temperature. Please note there are some PCB design guidelines to keep in mind for air temperature measurements. Most importantly, there should be low thermal conductivity between the PCB and the temperature sensor, to ensure that the sensor reads the ambient air temperature and NOT the temperature of the PCB or nearby components. You may refer to this app note for specific guidelines and suggestions: Temperature sensors: PCB guidelines for surface mount devices.

    The TMP112 "Address Variant" (TMP112D) has an Address Select pin that provides 4 I2C address options. The TMP112 "Alert Variant" (TMP112D0, TMP112D1, TMP112D2, TMP112D3) has an Alert pin instead of the Address Select pin, and has 4 I2C address options. Please see the table below for all of the address options on the TMP112. 

    If the customer requires 8 devices on 1 I2C bus, I recommend to use 4 TMP112D, 1 TMP112D0, 1 TMP112D1, 1 TMP112D2, 1 TMP112D3. The TMP112D devices should have their ADD0 pins configured to use all 4 I2C address options. The other 4 devices may have the Alert pin grounded if it's not needed. Here is an example schematic with a similar device that has 8 temperature sensors: 

    Best,

    Sakeenah 

  • 0 in reply to Sakeenah Khan
    Genius 3635 points

    Hi team,

    But this way will cause many PN in this BOM. Do you have other way to design? thanks 

  • 0 in reply to Jimmy WANG
    TI__Intellectual 2405 points

    Hi Jimmy,

    This is the only way to get 8 address options on TMP112. I am happy to suggest another part number if you want to share your requirements? Such as accuracy, size, package, communication protocol, etc. 

    Best,

    Sakeenah

  • 0 in reply to Sakeenah Khan
    Genius 3635 points

    Hi Sakeenah,

    Spec similar with TMP112 is okay. another question is why temp sensor design many package? will cause heat issue? 

    or any concern? thanks  

  • 0 in reply to Sakeenah Khan
    Genius 3635 points

    Hi Sakeenah,

    Is there any other solution to use I2C to assign addresses? Thanks 

  • 0 in reply to Jimmy WANG
    TI__Intellectual 2405 points

    Hi Jimmy,

    We offer many different device packages because of different # of pins, PCB area concerns, and other customer needs. Whichever sensor you choose, it is still important to follow ensure low thermal conductivity between the PCB and the temperature sensor in order to accurately measure the ambient air temperature. The previously referenced app note has guidance on PCB design for temperature sensors. 

    Digital ICs have address pin(s) to set the I2C bus address. This includes the TCA9548A, which has 3 address pins to support 8 devices on an I2C bus with distinct bus addresses. 

    A similar device to TMP112 is the TMP275. Both devices have 0.5°C accuracy. TMP275 has 3 address pins to support 8 I2C bus addresses. It is mostly software compatible to TMP112, the main difference being that TMP112 has an extended mode (which allows measurement of temperatures above 128°C). TMP275 is a bit larger than TMP112, and comes in VSSOP (3mm x 3mm) or SOIC (4.9mm x 3.91mm) packages. TMP275 also has a different power supply range of 2.7V-5.5V, meanwhile the TMP112 has a power supply range of 1.4-3.6V. 

    You may also check out our portfolio of digital temperature sensors here, and filter by parameters such as addresses, accuracy, package, power supply, etc. 

    Best,

    Sakeenah