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  • TI Thinks Resolved

TPD12S016: SDA/SCL_B pin capacitance

Prodigy 70 points

Replies: 13

Views: 1634

Part Number: TPD12S016

Greetings,

We just had some HDMI compliance tests run on our unit which incorporates your TPB12S016.  We failed DDC/CEC Line Capacitance and Voltage.  The Capacitance is too high 650p on SDA  and 950p on SCL. 

While I do not have a LCR bridge that can be set per the test procedure (bias 2.5V, AC voltage 3.5V, Freq 100K) using my LCR bridge (10K, 1V, no bias)  I measure a total Jig+unit capacitance of ~30p without the chip, and 120/190p with the chip (Jig capacitance ~12p). 

We are connected as a sink, SDA/SCL go to port B.  My interpretation of your data sheet shows input C at 15p.  My measured connector/track capacitance is ~18p, so 18p + your 15p  would be 33p and within the speced 50p max...  

Any feedback would be helpful

Thanks

Ed

  • In reply to Ed Judziewicz:

    The reduction of amplitude was their suggestion. They said that if we reduce the sine wave to below the trigger threshold of the edge rate enhancement, we should be able to measure the capacitance,
  • In reply to Chuck Branch:

    The HDMI spec requires the measurement be performed with a 3.5V p-p signal biased at 2.5V. How would that help me pass compliance?
  • In reply to Ed Judziewicz:

    Other companies have passed compliance with this ic. I assume that they have received a waiver for an alternative measurement technique because the edge rate enhancer will interfere with the measurement as defined.

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