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Inquiry regarding quiescent current on TMP112

Atsushi Okui
Genius 4015 points
Other Parts Discussed in Thread: TMP112

Hello, all

Now we are evaluating TMP112, then would like to know the detail on this quiescent current.

Please refer to the item below, and feedback us with your comment.

On page 9 of this datasheet, the active quiescent current during conversion is 40uA.

Meanwhile, on Figure 4 of page 4, this maximum quiescent current is 10uA (120 degree).

Please let us clarify which current value should be referred.

Thank you in advance for your information.

Best regards,

  • 0
    TI__Expert 7945 points

    Hello Atsushi-San,

    7uA is the average quiescent current for the default conversion rate 4Hz while the max average quiescent current is 10uA for the max configurable conversion rate of 8Hz. 

    Let me explain this in detail with an example while referring to the Page 9 of datasheet that you mentioned:

    During the conversion Iq= 40uA  (26mS interval as shown above)

    Between Conversions Iq= 2.2uA

    So for Example lets say we programmed the part to 8Hz- max conversion rate.

    8Hz= 125mS conversion time intervals = 26ms during conversion+99ms time between conversions.

    Therefore                                Iq(Average) =( (26ms*40uA)                    + (99mms*2.2uA))/125mS

                                                                           = 10.062uA

    Hope this clears your doubts on Iq.

    Best Regards,

    Abhi Muppiri

    Applications Engineer

    AIP- Sensing Products

    Texas Instruments

  • 0 in reply to Abhishek Muppiri
    Genius 4015 points

    Hello, thank you for your reply.

    Based on your comment, please let us clarify regarding each items below;

    Q1.

    > Therefore  Iq(Average) =( (26ms*40uA) + (99mms*2.2uA))/125mS = 10.062uA

    => Is it possible for this device to transit into shut down mode without waiting 99ms, after issued the command from CPU and CPU has completed reading temperature data?

    Q2.

    With regard to the description of IQ which is mentioned as "Serial Bus Active, SCL Frequency = 400kHz" on datasheet page 3, is this considered for including current consumption while exchanging data, or only considered for I2C operation?

    We thank you once again for your information.

    Best regards,

  • 0 in reply to Atsushi Okui
    TI__Expert 7945 points

    Question: Is it possible for this device to transit into shut down mode without waiting 99ms, after issued the command from CPU and CPU has completed reading temperature data?

    Yes, it is possible to shut down the device in order to reduce power, its called "One Shot Mode (OS)". By using this mode you can perform a single conversion (40uA current) and then return to a shut down state (1uA current) which is best suited for applications that need low power and doesn't require continuous temperature monitoring. Moreinformation in how to operate in this mode is available on Page 10 of the Data sheet.

    Question: IWith regard to the description of IQ which is mentioned as "Serial Bus Active, SCL Frequency = 400kHz" on datasheet page 3, is this considered for including current consumption while exchanging data, or only considered for I2C operation?

    Iq in this case includes both the current due to conversions(default - 4Hz case) and the current due to SCL and SDA lines toggling during the communication with host. If you are interested in just the current consumed due to I2C  communication, please refer to Shut Down current (Isd)  located below Iq values table in Page 3 of the Data sheet.

    Hope I have answered your questions thoroughly....


    Best Regards,

    Abhi