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Original question:

DP141RLJEVM: I2C_EN setting for GPIO mode

DP141RLJEVM: how to use DRV_PK?

Gang Feng1
Prodigy 65 points
Part Number: DP141RLJEVM
Other Parts Discussed in Thread: SN65DP141

Hi,

In the EVM board, the J1 was used to "Disable/Enable Driver peaking". In what situations should I enable it?

I check the data sheet of sn65dp141, which only mentioned that "LOW: enables Driver 6-dB AC peaking". I don't know what it means. In my application, I have a 5m long passive DP cable that can pass 4K@60Hz video signals. I want to add a 3m~5m long cable with SN65DP141 EVM board, so that a 8m~10m long link is obtained. Should I enable the DRV_PK? 

Btw, can I get a schematic of the evm board? I couldn't find a download link of it.

thanks

  • 0
    TI__Guru**** 177726 points

    Hi,

    DRV_PK applies a AC gain on the TX side.

    I would put the DP141 on the far side of the 8m-10m cable so you can use the DP141 RX equalizer to compensate for the total insertion loss as much as possible. Please refer to table 3 in the DP141 datasheet for the proposed EQ setting.

    Attached is the DP141 schematic.

    INT029A_schematic.pdf

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 65 points

    Hi, David,

    The schematic really helps a lot to understand the settings.

    Is the AC gain means that the TX side will amplify the signals about 6dB over some frequency range?

    For the EQ gain mentioned in the date sheet, are they all measured at 6GHz? 

    In table 2 / table 3, the max gain range is 7~17dB. However, in the first page of the data sheet, it says "15-dB Analog Equalization at 6 GHz". I am confusing how much EQ gain can this chip achieve, 15 or 17 dB?

    Thanks,

  • 0 in reply to Gang Feng1
    TI__Guru**** 177726 points

    Hi,

    Yes, DRV_PK 6dB amplifies the signal at high frequency range.

    Yes, EQ gain is measured at 6GHz.

    The datasheet should clarify the difference between the 15dB and 17dB. The 15dB is at 6GHz, but the 17dB is measured at ~7GHz.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 65 points

    Hello,

    There is a signal chain gain control diagram (Figure 16 in page 14 of the data sheet). It shows that RX dc gain and TX dc gain are configurable. Since the total dc gain should be 0dB, there are actually only two possible configurations with the dc gains: (1) Rx dc gain = -6dB and TX dc gain=6dB; (2) Rx dc gain = 0dB and Tx dc gain = 0dB. Is this understanding correct?

    I didn't see the DRV_PK 6dB AC gain in this diagram. Can this Tx side 6dB AC gain stack on the EQ_AC_GAIN? Or, they are effective in different frequency range and won't affect each other?

    If the DP141 is put on the far side of the 8m-10m cable,  it is a long input cable case. According to Table 3, the Rx gain should be set to -6dB to get the 7-17 EQ AC gain. I guess in this case, the input swing may not be large. But there seems no setup method for long input cable small input swing?

    Thanks

  • 0 in reply to Gang Feng1
    TI__Guru**** 177726 points

    Hi,

    Please see my response in this e2e thread: .

    Thanks

    David