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TPD12S521

Michael Rourke
Intellectual 350 points
Other Parts Discussed in Thread: TPD12S521

Is there any particular reason 47K ohm pull-up resistors are shown on the DCLK_IN and DDAT_IN lines? Shouldn't these typically be around 1.7K ohms (depending on the I2C driver)?

  • 0
    TI__Genius 12190 points
    Michael,

    The HDMI spec requires 1.7 k-ohm pull-ups on SCL and SDA for the source. The TPD12S521 pull-ups on the connector side match that, which is the correct way to look at it. The reason 47 k-ohm pull-ups between the core chip and the TPD12S521 were chosen is that we would consider the core chip was designed to drive a sink with 47 k pull-ups.

    Regards,
  • 0 in reply to Guy Yater
    Intellectual 350 points
    Guy, thanks for the quick reply.

    So the 47k ohm pull ups were just place holders? Since our I2C interface already has its own pull-ups on the clk and data lines, then I take it we don't need the 47k's?
  • 0 in reply to Michael Rourke
    TI__Genius 12190 points

    Hi Michael,

    That's correct, if you already have pull-ups don't use more as long as you have 47k or less already. If you have, say 100k internal, you should put 89k pull-ups as shown in the data sheet where the 47k are. This would give 47k from 100k||89k. 

    Regards,