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DS125DF410 question

Other Parts Discussed in Thread: DS125DF410, DS100BR410

Dear all:

We are designing a Display Port cable with using DS125DF410 chip, the cable length is (5-15)m/28AWG,and the lost is (10-34)db for 2.7Ghz. The Display Port work frequency is 1.62Ghz or 2.7Ghz. For example, configure mode2 or mode3(adaptive),but it was unlock at all. it was no image at any time. I thought that the CDR lock time is very slow when DP is traning. So I setup at mode 0, and then setup CTLE(0x03 0x3a 0x40) for manual and setup VCO frequency, I thought the CDR lock time is fast. This chip can output singal and locking(0x02=0xdc), but somting have unstable or boost is slow. Finally I setup raw data, it alway can be output normal signal and display is OK at any timing. do you have any suggestion about the CDR lock to give me or do you have any applications for the Display Port?


The manually register was setup below
//mode 0 //manual mode
{0x36,0x31}, //with a 25Mhz reference clock,reference clock mode[5:4],field=3[1:0]
{0x2f,0x66}, //{0x2f,0x62}, //Divider ratios 8/or 4/ or 2/or 1/,10.8Ghz/4=2.7Ghz,false lock detector is enable[1]=0
{0x60,0xcd}, //{0x60,0x00}, //PPM count,group 0, divider ratio 8, 10.8Ghzx1280=13824(0x3600)
{0x61,0xc0}, //{0x61,0xb0}, //PPM count,group 0, divider ratio 8, bit7=1(manual load)
{0x62,0x00}, //PPM count,group 1,divider ratio 8, 12.96Ghzx1280=16589(0x40CD)
{0x63,0xb0}, //PPM count,group 1,divider ratio 8, bit7=1(manual load)
{0x64,0xff}, //PPM count tolerance,(1x0.000001xNtol)/Nppm=TOLppm,=1085
{0x31,0x00}, //mode0,adapt CTLE until lock,then DFE, then EQ until optimal
{0x1e,0x29}, //retimer data
{0x3a,0xc5}, //EQ
{0x03,0xc5},
{0x40,0xc5},

best regard!

Bob Yang

  • Hi Bob,

    From your email I'm not sure exactly which datarates you need to support?  Displayport has many possible rates including 1.62, 2.7, 5.4 and 8.1 Gbps.

    For the DS125DF410 to lock it will need to be programmed with the exact datarate that it is receiving.  Also, some of these data rates are outside the VCO operating range.  The DS125DF410 VCO range is 9.8 - 12.5 GHz, this VCO range allows the device to lock within the ranges shown below.

    VCO        9.8 Gbps - 12.5 Gbps

    VCO/2     4.9 Gbps - 6.25 Gbps

    VCO/4     2.45 Gbps - 3.125 Gbps

    VCO/8     1.225 Gbps - 1.5625 Gbps

    The DS100BR410 offers a similar footprint and uses linear equalization to compensate for cable loss.  It is likely a better choice.

    Regards,

    Lee

  • Hi Lee:
    Thanks very much. I see. That is to say, it is OK if working frequency is 2.7Ghz or 5.4Ghz. I will setup these to do. Thanks.

    have a nice weekend,

    Bob Yang