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SN65DP159 Device Protection?

juho kim
Prodigy 160 points
Other Parts Discussed in Thread: SN65DP159

Hello... 

We use SN65DP159 in redriver mode... and the device often dies, which means one of TMDS Output Channel does not working..

I connected TMDS output directly to the HDMI Connector with no termination and 3.3V Termination is on the Receiver Side.. and do not use auto power down.

My guess is

    (1) SN65DP159 is damaged when HDMI Cable Connects on and off.. (since there is no ESD protection diode)

    (2) if  one of TX and RX Board is not powered on,  the chip is damaged by current injection.

    (3) TMDS Output driving with no termination may damage the chip. (when cable is not connected..)

I wonder what is the main reason of the chip damage.. Is there any experience about this ?

What is the correct connection of the chip to be protected safely?

One more question is as below :

   According to the datasheet, input signal is terminated on Vbias inside chip and it looks like 0.7V... but when I monitored with oscilloscope, VCM of input signal is almost 0V. Is that right?? I thought it would be higher then 0V, some level between 0V and 0.7V..  (input signal is ac-coupled.)

  • 0
    TI__Guru* 76130 points
    Sorry for the delay, we have assigned this to the appropriate support engineer and he will respond soon.
    Regards
  • 0 in reply to Elias Villegas M.
    TI__Mastermind 23815 points
    Hi Juho,

    We haven't seen this behavior, could you share schematics for review?

    Regards
  • 0
    TI__Mastermind 23815 points

    Hi Juho,

    I'm reviewing your schematics.

    Since this is a public forum I will delet your previous post with your files.

    Regards

  • 0 in reply to Moises Garcia
    TI__Mastermind 23815 points
    Hi Juho,

    Could you elaborate about your application and failing behavior?
    I see you have two boards, Tx with DP159 and Rx with an FPGA and a display?

    When the device dies, you say so because there is no video or you don't even have access to internal registers?
    are you able to measure output HDMI signals? selecting a small resolution and slow refresh rate could lead to frequencies that can be measured with a not so advance scope.

    From the display control, do you still see listed the display?

    Why you have routed DDC from connector to FPGA(eith level shifter) and from connector to FPGA through DP159?
    DP159 requires 2k pullups on SCL_SNK/SDA_SNK to do snooping when changing to HDMI2.0 data rates

    Regards
  • 0 in reply to Moises Garcia
    Prodigy 160 points

    Hello...

    We use SN65DP159 as a redriver IC... We don't follow HDMI protocol...

    When it fails, one of the 4 TMDS channel doesn't send output signals..  there is no differential signals..  

    and we don't use DDC channel of SN65DP159...    

    There is no display because we use the channel as a datapath..

    To summarize, 

             (1) We use SN65DP159 as a Re-Driver IC of our own signal protocol, and do not use DDC of SN65DP159.

    (2) When it fails, one of the 4 output of SN65DP159 is dead, which means no differential output signal even though input signal is alive..

    (internal register access is ok..)

    Regards,

  • 0 in reply to juho kim
    TI__Mastermind 23815 points

    Hi Juho,

    Since this is not a DP/HDMI application it will be hard to debug the problem.

    What is the data rate of your protocol?

    Receiver has 50ohms resistors(RES510)?

    Caps are 100nf(CAP104)?

    The failing channel is always the same?

    In HDMI CLK lanes has a data rate 10 times slower, to support higher data rate there you need to configure it in x-mode.

    Could you measure the current in output pins?

    Regards

  • 0 in reply to Moises Garcia
    Prodigy 160 points

    Hello, Garcia .

    Receiver has 50 ohms(RES510) and 100nF(CAP104) Caps..

    Datarate of each channel is 2.5GBps(or 3.125 GBps).

    When I measure the voltage on the 50 ohm pull-up resistor, the voltage swing is about 400 ~ 500mVpp .. and I think this is less than what I expected..

    (1) How can I increase the output voltage swing? 

    (2) What is x-mode in HDMI CLK lane? How can I configure? Can I use HDMI CLK lane as 2.5GBps data channel??

    (3) What is the VCM of Input port? Datasheet says that it's 0.7V and My measurement shows about 0V..  SN65DP159 has input pullup resistor inside of the chip, right?

    I'm not sure what is the correct status of input and output voltage.. it's VCM and Vdiff is less than that of datasheet... 

    Regards,

  • 0 in reply to juho kim
    TI__Mastermind 23815 points

    Hi Juho,

    1) You can reduce the value of Rvsadj, refer to datasheet figure 19

    2) Check DP159 as DP retimer application note http://www.ti.com/lit/pdf/slla358

    3) I would say it has pullups, I would say it has terminations to bias voltage.

    So let's recapitulate,

    You want to use DP159 in a non DP/DP++_HDMI application

    Data rate is 3.125Gbps top

    Input signals are AC coupled, desired output signals are AC coupled too.

    You have DP159 in I2C mode, with default configuration?

    We cannot provide support for this kind of applications, but I think you are using the wrong device.

    DP159 is intended as DP++ to HDMI2.0(6Gbps) level shifter, this is HDMI signal AC coupled at the input and TMDS signals at the output. In HDMI1.4 clock lane has a frequency ten times slower than data lines data rate, in HDMI2.0 clock lane has a frequency forty times slower than data rate.

    By default DP159 works as DP++ to HDMI level shifter, it will expect a clock signal on clock lane, by default DP159 will switch to retimer mode at 1Gbps, the clock in clock lane will be recovered, and there will be a ratio between data lanes rate and clock frequency of x10 before 3.4Gbps and x40 from 3.4 to 6 Gbps.

    If you are looking for a general purpose redriver with characteristics similar to video transmission, you may want to check DP130, this device is a DP redriver, input and output signals are AC coupled, all lanes have the same data rate, there is no clock recovery, supports up to 5.4Gbps, you just have to configure it by I2C using the available application note.

    Regards