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HD3SS215 DDCx pull-up resistor

NAOKI AOYAMA
Guru 11215 points
Other Parts Discussed in Thread: HD3SS215

Hello,

Our customer use the HD3SS215, using 2 sink application like the Figure 7 on the datasheet.

The customer's configuration as follows

 AUX_SEL : M

Dx_SEL : H

OE : H

insert pull-up resistor at port C to +5V as 2kohm

communicate from port C to port B

When the customer input 5V to port C, the output voltage at port B is 4V.

Does it need a pull-up resistor at port B to +5V, too ?

Best Regards,

Naoki Aoyama

  • 0
    TI__Mastermind 23815 points

    Hi Naoki,

    I guess the pullups you mention are the ones on DDC, the idea to have the pull-ups on port C is to just have one pair of pull-ups.

    Do you see the same voltage drop on PORTA?

    Could you measure the voltage drop between PORTC and PORTA/PORTB?

    Could they measure the DC resistance between PORTC and PORTA/PORTB? it should be maximum 40ohms

    Have they tried a different IC?

    Regards

  • 0 in reply to Moises Garcia
    Guru 11215 points
    Hi Moises,

    Thank you for your reply.
    I will ask the customer measure the voltage and resistance.

    Regards,
    Naoki Aoyama
  • 0 in reply to Moises Garcia
    Guru 11215 points
    Hello Moises,

    The customer check the voltage.
    The voltage of port A is 4V.
    The customer could not measure the resistance.

    The customer tried some sink monitor, notice it occur only one manufacture.
    HDMI is standard, so I think there is no difference between manufactures.
    What is consider about this issue?

    Regards,
    Naoki Aoyama
  • 0 in reply to NAOKI AOYAMA
    TI__Mastermind 23815 points

    Hi Naoki,

    I got a little confused, this measurement was done with a monitor connected?

    Have they measured without monitors?

    What is the voltage level on PORTC?

    Could they measure the voltage of DDC lines in failing monitor?

    If there is only one monitor with 4V, this could be because the monitor has a different voltage, maybe 3.3V with 2k pull-ups which would lead to have around 4V on PORTA/PORTB.


    Regards