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Original question:

TMP441: Calculating temperature error after NF correction on TMP441/442 and alternatives for I1 and I2

TMP441: values for the currents source

Renan Santos Adriano
Mastermind 22380 points
Part Number: TMP441

Hello Team,

Posting on be half of my customer:

We know that the Remote Sensor Source Currents 6uA (low), 12uA (medium low), 60uA (medium high) and 140uA(high) can't be set to any other values. What does 'medium low' and 'medium high' current mean in this case? The diode I am using can't support the high current. I am trying to see if the part will source lower current and still use this part.  

Regards,
Renan

  • 0
    TI__Mastermind 43875 points

    Slight correction: its 120uA not 140uA. All of the currents are being used as part of the algorithm. The high current can't be avoided or disabled. This is true for all remote sensors on the market that I'm aware of. What is the application and current limit? This feedback will help our future developments.

    thanks,

    ren

  • 0 in reply to Ren Schackmann
    TI__Mastermind 22380 points

    Hello Ren,

    Good day.

    Please see response from my customer:

    Is this part only supposed to interface with remote BJT on a board or platform? What is the remote BJT is part of an IC (SoC)? Is there a specification for the remote BJT? It seems based on the response that the remote BJT is supposed to be handle the above mentioned currents. Is the remote BJT spec a IEEE standard? If the remote BJT is on an IC how do you guarantee that the currents sourced doesn't move the 'region of operation' to somewhere where the 'ideality factor' is not 1?

    Regards,

    Renan

  • 0 in reply to Renan Santos Adriano
    TI__Mastermind 43875 points

    The remote sensors, such as TMP441, are designed to work with both embedded and discrete junctions. TMP441 has the Beta Compensation feature which was specifically created to address an issue in embedded junctions built in <45nm process technology. This feature is proof that we are happy to accommodate the needs of the market. As I stated previously, I'm not aware of junctions that are incompatible with 120uA. If you could please share further detail on your application, it would help our future product definition. Unfortunately, that doesn't change the fact that all of the remote sensors available today produce over 100uA biasing current.

    No, remote BJT is not a IEEE standard. The remote sensor market has standardized around the 2N3906/2N3904 discrete transistors and their variants as well as some specific PC applications with embedded junctions. We can't be accountable for variations in junctions; it's outside our control. In the case of Beta Compensation, we were able to create a work-around for a specific case of bad junction behavior. 

    For more information on our approach to junctions, please see the applications note http://ti.com/lit/sboa433 which has the following criteria for junction selection:

    thanks,

    ren