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TMP103: TMP103AYFF | VIH is failing

felix thomas
Prodigy 80 points
Part Number: TMP103

Hi Team,

Please find the below-summarised table for the temperature sensor values measured.

Here Max VIH is failing, The supply voltage is 1.8V and the waveform seems okay. Could you please tell me why? 

  • Table below shows the summariesed data measured
    Sensor-TMP103
    Signal Symbol Min Max Measured Units Result
    TEMP_EPR_I2C_SCL
    		 VIH 1.26 1.8 2.0188 V FAIL
    VIL -0.5 0.54 -0.147 V PASS
    TEMP_EPR_I2C_SDA
    		 VIH 1.26 1.8 1.9796 V FAIL
    VIL -0.5 0.54 -0.0882 V Pass

  • The image is taken from the datasheet

  • The image below shows the Schematics used. and the waveform is probed from R174 and R175 resistors
  • Below is the probed image from MSO 
  • 0
    TI__Mastermind 39655 points

    Hi Felix,

    I don't see a source of 2V anywhere in your schematic. How are you testing VIH? If you are sourcing current into SCL/SDA pins, you must clamp your instrument at 1.8V. Sourcing current this way would detect the structures responsible for TMP103's unique absolute max spec. TMP103 does not allow SCL/SDA voltages to exceed V+. This limitation comes from the low pin count; other I2C TMP have more pins and don't have this voltage limitation.

    ren

  • 0 in reply to Ren Schackmann
    Prodigy 80 points

    Hi Ren,

    1. Below power scheme is used for VCC_1V8_IO generation 

    2. We use MSO to probe the VIH(from resistor R174 and R175). 

  • 0 in reply to felix thomas
    TI__Mastermind 39655 points

    How do you test VIH?

    thanks,

    ren

  • 0 in reply to Ren Schackmann
    Prodigy 80 points

    Hi Ren, 

    Didn't get what you are asking.

    1. We have used Oscilloscope to probe the VIH(from resistor R174 and R175), which was found higher than supply voltage 1.8.

    2. We are measuring the temperature value and found it to be okay.

    3. Clock and Input waveform is also attached below. From the waveform it is clear that VIH is higher than input voltage

  • 0 in reply to felix thomas
    TI__Mastermind 39655 points

    This voltage level that you show on the oscilloscope is not VIH. VIH is an input specification. The VIH spec is tested by varying the input voltage to see what voltage is needed for TMP103 to detect logic high. 

    The voltage level is determined by your pull-up resistors' supply voltage. Your schematic specifies the voltage as 1.8V. Either your pull-up voltage is not 1.8V, your oscilloscope is not calibrated, or some combination of the two. The only way TMP103 would contribute to voltage level is if the SCL/SDA voltage exceeded TMP103's supply voltage, it would then try to pull down the voltage. That is not the case in your schematic, and the symptom you are reporting is that the voltage is pulled above supply. 

    ren

  • 0 in reply to Ren Schackmann
    Prodigy 80 points

    Hi Ren,

    For the pull-up and supply voltage, there is no change. They are shorted to 1.8V supply. From the above discussion what i understood is that.

    • 1.26 to 2.1V will consider as logic 1
    • -0.5 to 0.56V is considered as logic 0

     Please confirm these values if the supply voltage is 1.8V.

    Figure 1 : From the datasheet

    Figure 2 : Edited for our values.

  • 0 in reply to felix thomas
    TI__Mastermind 39655 points

    Seems reasonable to me.

    ren