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IC has pull-down resistors on SMBus lines?



The Next CEO of Stack OverflowMOSFET and clamp on I2C interface lines as level tranlastorSMBus with AVR?i2C : pull-up resistors “design pattern”, Shielded cable and connector?I2C protocol debugging using oscilloscopePS2 / SMBus communicationDoes SMBus spec lie about I2C?If a datasheet doesn't state I2C address pins have pull-up/down resistors, does that mean I must connect them?I2C device lists 20mA max current on AD, CL, and DA pins. Do I need a resistor between it and Arduino?SMBus Address and BaudRateSMBus v1.1 voltage threshhold value










3












$begingroup$


The datasheet of TI bq40z50-R2 (Li-Ion Battery Pack Manager) tells that "The SMBus clock and data lines have internal pulldown".



Pin equivalent Diagram is in image below:
Pin equivalent Diagram



Aren't usually the SMBus Data and Clock lines to be connected to pull-up resistors?



I'd like to connect this IC and a Battery Charger IC to same SMBus, but the latter requires pull-up resistors for the SMBus lines.



Would this work anyway?



Thanks










share|improve this question









$endgroup$
















    3












    $begingroup$


    The datasheet of TI bq40z50-R2 (Li-Ion Battery Pack Manager) tells that "The SMBus clock and data lines have internal pulldown".



    Pin equivalent Diagram is in image below:
    Pin equivalent Diagram



    Aren't usually the SMBus Data and Clock lines to be connected to pull-up resistors?



    I'd like to connect this IC and a Battery Charger IC to same SMBus, but the latter requires pull-up resistors for the SMBus lines.



    Would this work anyway?



    Thanks










    share|improve this question









    $endgroup$














      3












      3








      3





      $begingroup$


      The datasheet of TI bq40z50-R2 (Li-Ion Battery Pack Manager) tells that "The SMBus clock and data lines have internal pulldown".



      Pin equivalent Diagram is in image below:
      Pin equivalent Diagram



      Aren't usually the SMBus Data and Clock lines to be connected to pull-up resistors?



      I'd like to connect this IC and a Battery Charger IC to same SMBus, but the latter requires pull-up resistors for the SMBus lines.



      Would this work anyway?



      Thanks










      share|improve this question









      $endgroup$




      The datasheet of TI bq40z50-R2 (Li-Ion Battery Pack Manager) tells that "The SMBus clock and data lines have internal pulldown".



      Pin equivalent Diagram is in image below:
      Pin equivalent Diagram



      Aren't usually the SMBus Data and Clock lines to be connected to pull-up resistors?



      I'd like to connect this IC and a Battery Charger IC to same SMBus, but the latter requires pull-up resistors for the SMBus lines.



      Would this work anyway?



      Thanks







      i2c smbus






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 1 hour ago









      haku15haku15

      726




      726




















          1 Answer
          1






          active

          oldest

          votes


















          5












          $begingroup$

          The internal pull-downs in question are very weak, 1 MΩ. They are not meant to be "operational", and won't have any effect on normal I2C data transactions when the standard (10k-5k or 2k) pull-ups are attached to the I2C system bus. The reason for weak pull-downs is to provide well-defined bus state during power-on transients, when not all parts of the system are yet powered up.



          The initial state with pull-downs is used by internal logic of the IC, per datasheet P.34:




          When the gas gauge senses that both lines are low (such as during
          removal of the pack),the device performs auto-offset calibration and
          then goes into SLEEP mode to conserve power"







          share|improve this answer











          $endgroup$












          • $begingroup$
            Just a tip: you can use HTML symbols in the posts. &Omega;, &mu;, &deg;, etc. For superscripts and subscripts use HTML <sup>...</sup> and <sub>...</sub>. They don't work in the comments.
            $endgroup$
            – Transistor
            46 mins ago










          • $begingroup$
            Ok, thanks for the explanation!
            $endgroup$
            – haku15
            2 mins ago











          Your Answer





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          1 Answer
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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          5












          $begingroup$

          The internal pull-downs in question are very weak, 1 MΩ. They are not meant to be "operational", and won't have any effect on normal I2C data transactions when the standard (10k-5k or 2k) pull-ups are attached to the I2C system bus. The reason for weak pull-downs is to provide well-defined bus state during power-on transients, when not all parts of the system are yet powered up.



          The initial state with pull-downs is used by internal logic of the IC, per datasheet P.34:




          When the gas gauge senses that both lines are low (such as during
          removal of the pack),the device performs auto-offset calibration and
          then goes into SLEEP mode to conserve power"







          share|improve this answer











          $endgroup$












          • $begingroup$
            Just a tip: you can use HTML symbols in the posts. &Omega;, &mu;, &deg;, etc. For superscripts and subscripts use HTML <sup>...</sup> and <sub>...</sub>. They don't work in the comments.
            $endgroup$
            – Transistor
            46 mins ago










          • $begingroup$
            Ok, thanks for the explanation!
            $endgroup$
            – haku15
            2 mins ago















          5












          $begingroup$

          The internal pull-downs in question are very weak, 1 MΩ. They are not meant to be "operational", and won't have any effect on normal I2C data transactions when the standard (10k-5k or 2k) pull-ups are attached to the I2C system bus. The reason for weak pull-downs is to provide well-defined bus state during power-on transients, when not all parts of the system are yet powered up.



          The initial state with pull-downs is used by internal logic of the IC, per datasheet P.34:




          When the gas gauge senses that both lines are low (such as during
          removal of the pack),the device performs auto-offset calibration and
          then goes into SLEEP mode to conserve power"







          share|improve this answer











          $endgroup$












          • $begingroup$
            Just a tip: you can use HTML symbols in the posts. &Omega;, &mu;, &deg;, etc. For superscripts and subscripts use HTML <sup>...</sup> and <sub>...</sub>. They don't work in the comments.
            $endgroup$
            – Transistor
            46 mins ago










          • $begingroup$
            Ok, thanks for the explanation!
            $endgroup$
            – haku15
            2 mins ago













          5












          5








          5





          $begingroup$

          The internal pull-downs in question are very weak, 1 MΩ. They are not meant to be "operational", and won't have any effect on normal I2C data transactions when the standard (10k-5k or 2k) pull-ups are attached to the I2C system bus. The reason for weak pull-downs is to provide well-defined bus state during power-on transients, when not all parts of the system are yet powered up.



          The initial state with pull-downs is used by internal logic of the IC, per datasheet P.34:




          When the gas gauge senses that both lines are low (such as during
          removal of the pack),the device performs auto-offset calibration and
          then goes into SLEEP mode to conserve power"







          share|improve this answer











          $endgroup$



          The internal pull-downs in question are very weak, 1 MΩ. They are not meant to be "operational", and won't have any effect on normal I2C data transactions when the standard (10k-5k or 2k) pull-ups are attached to the I2C system bus. The reason for weak pull-downs is to provide well-defined bus state during power-on transients, when not all parts of the system are yet powered up.



          The initial state with pull-downs is used by internal logic of the IC, per datasheet P.34:




          When the gas gauge senses that both lines are low (such as during
          removal of the pack),the device performs auto-offset calibration and
          then goes into SLEEP mode to conserve power"








          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 42 mins ago

























          answered 50 mins ago









          Ale..chenskiAle..chenski

          28.9k11866




          28.9k11866











          • $begingroup$
            Just a tip: you can use HTML symbols in the posts. &Omega;, &mu;, &deg;, etc. For superscripts and subscripts use HTML <sup>...</sup> and <sub>...</sub>. They don't work in the comments.
            $endgroup$
            – Transistor
            46 mins ago










          • $begingroup$
            Ok, thanks for the explanation!
            $endgroup$
            – haku15
            2 mins ago
















          • $begingroup$
            Just a tip: you can use HTML symbols in the posts. &Omega;, &mu;, &deg;, etc. For superscripts and subscripts use HTML <sup>...</sup> and <sub>...</sub>. They don't work in the comments.
            $endgroup$
            – Transistor
            46 mins ago










          • $begingroup$
            Ok, thanks for the explanation!
            $endgroup$
            – haku15
            2 mins ago















          $begingroup$
          Just a tip: you can use HTML symbols in the posts. &Omega;, &mu;, &deg;, etc. For superscripts and subscripts use HTML <sup>...</sup> and <sub>...</sub>. They don't work in the comments.
          $endgroup$
          – Transistor
          46 mins ago




          $begingroup$
          Just a tip: you can use HTML symbols in the posts. &Omega;, &mu;, &deg;, etc. For superscripts and subscripts use HTML <sup>...</sup> and <sub>...</sub>. They don't work in the comments.
          $endgroup$
          – Transistor
          46 mins ago












          $begingroup$
          Ok, thanks for the explanation!
          $endgroup$
          – haku15
          2 mins ago




          $begingroup$
          Ok, thanks for the explanation!
          $endgroup$
          – haku15
          2 mins ago

















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