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DS90UH947-Q1: There is no signal on the LF pin of ds90uh947.

choi jeongho
Prodigy 160 points
Part Number: DS90UH947-Q1


I am developing using ds90uh947 and ds90uh948.
The LF pin of the ds90uh947 is "FPD-Link III Loop Filter", which connects 10nF to GND. The oscilloscope is supposed to show the signal, but I can't see any signal. How many volts should a signal be normal?

  • 0
    TI__Mastermind 30515 points

    Jeongho,

    we'll check it later, thank you to touch us for it.

    best regards,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    Prodigy 160 points

    Steven. Thanks for the answer.

    I have a board that works fine, not something I developed. LF signal comes out about 1 volt. The PLL of FPD Link III seems to work normally.

    By the way, the board I am developing has LF signal of 0volt. FPD Link III does not seem to work. Actually, ds90uh947 and ds90uh948 of the board under development are connected and the video is received and ds90uh948 is outputting normally.
    However, some boards show instability, such as flickering. I think the signal on the LF pin is important.

    The resolution used is 1920x720 (PCLK = 89MHz) and "OpenLDI Dual" and "FTD LINK III Single" are used.

    Please let me know how the output of LF pin is normal.

    Thank you.

  • 0 in reply to choi jeongho
    TI__Mastermind 30515 points

    Hi,

    We just check the LF pin20 in our EVM. the voltage is different for diff. use case such as temp., PCLK freq., etc., generally it is about several hundreds mV level.

    But this voltage should not impact on your the flickering issue. Please check if the link has bit error and unlock issue. If yes, please check the link analysis, such as FPD-Link channel single/dual setting, PCLK jitter, cable / connector S11/S21 parameters, etc.

    best regards,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    Prodigy 160 points

    Hi, Steven

    Thank you for your quick response.

    I need to check what you said about the issues that flicker.

    But I still don't understand the LF pin. If the LF pin acts as a loop filter for the FPD-LINK PLL, then it is thought that the VCO will work when the output is hundreds of millivolts.
    Does outputting zero volts mean the PLL is not working properly?

    And I wonder if there are registers that configure the FPD-LINK PLL. Is there "FPD3 TX Registers" in "Analog register select". Do I have to set these registers so that I can see the output of the LF pin?

    best regards,

  • 0 in reply to choi jeongho
    TI__Mastermind 30515 points

    Hi,

    Regarding the LF pin, it has wide operation range. generally this pin is used one 0.01uf cap. for filter. Yes, it has some registers for the PLL, but unfortunately, these registers are not released.

    For your issue, how many boards record the LF pin as 0v? whether the link is working when you measure it? thanks.

    best regards,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    Prodigy 160 points

    Hi.

    I made five boards, three with blinking symptoms and two with no blinking symptoms. But all five LF pins come out 0v.

    A 0.01uF capacitor is connected to GND on the LF pin.

    The chip is set as follows. HDCP is also on.

    Reg0x40 = 0x10 // select OLDI register
    Reg0x41 = 0x49 // force PLL controller in PPM reset state
    Reg0x42 = 0x16
    Reg0x41 = 0x47 // force PLL LOCK Low
    Reg0x42 = 0x20
    Reg0x42 = 0xA0 // reset PLL divider
    Reg0x42 = 0x20
    Reg0x42 = 0x00 // release PLL LOCK control
    Reg0x41 = 0x49 // release PLL state control
    Reg0x42 = 0x00

    Below is a dump of the data on the chip.
    addr: data
    00h: 18h
    01h: 00h
    02h: 00h
    03h: D2h
    04h: 80h
    05h: 00h
    06h: 58h
    07h: 00h
    08h: 00h
    09h: 00h
    0Ah: 00h
    0Bh: 00h
    0Ch: 05h
    0Dh: 00h
    0Eh: 00h
    0Fh: 00h
    10h: 00h
    11h: 00h
    12h: 00h
    13h: B8h
    14h: 00h
    15h: 01h
    16h: FEh
    17h: 1Eh
    18h: A1h
    19h: A5h
    1Ah: 00h
    1Bh: 00h
    1Ch: 00h
    1Dh: 00h
    1Eh: 01h
    1Fh: 00h
    20h: 0Bh
    21h: 00h
    22h: 25h
    23h: 00h
    24h: 00h
    25h: 00h
    26h: 00h
    27h: 00h
    28h: 00h
    29h: 20h
    2Ah: 00h
    2Bh: 80h
    2Ch: 00h
    2Dh: 00h
    2Eh: A5h
    2Fh: 5Ah
    30h: 00h
    31h: 00h
    32h: 00h
    33h: 00h
    34h: 00h
    35h: 00h
    36h: 00h
    37h: 00h
    38h: 00h
    39h: 00h
    3Ah: 00h
    3Bh: 00h
    3Ch: 00h
    3Dh: 00h
    3Eh: 00h
    3Fh: 00h
    40h: 00h
    41h: 00h
    42h: 00h
    43h: 00h
    44h: 80h
    45h: 00h
    46h: 63h
    47h: 00h
    48h: 00h
    49h: 00h
    4Ah: 00h
    4Bh: 00h
    4Ch: 00h
    4Dh: 00h
    4Eh: 00h
    4Fh: C0h
    50h: 16h
    51h: 00h
    52h: 00h
    53h: 00h
    54h: 02h
    55h: 00h
    56h: 00h
    57h: 00h
    58h: 00h
    59h: 00h
    5Ah: CDh
    5Bh: 20h
    5Ch: 02h
    5Dh: 26h
    5Eh: 44h
    5Fh: 3Fh
    60h: 00h
    61h: 00h
    62h: 00h
    63h: 00h
    64h: 10h
    65h: 00h
    66h: 00h
    67h: 00h
    68h: 00h
    69h: 00h
    6Ah: 00h
    6Bh: 00h
    6Ch: 00h
    6Dh: 00h
    6Eh: 00h
    6Fh: 00h
    70h: 00h
    71h: 00h
    72h: 00h
    73h: 00h
    74h: 00h
    75h: 00h
    76h: 00h
    77h: 00h
    78h: 00h
    79h: 00h
    7Ah: 00h
    7Bh: 00h
    7Ch: 00h
    7Dh: 00h
    7Eh: 00h
    7Fh: 00h
    80h: C3h
    81h: CAh
    82h: 47h
    83h: E0h
    84h: 3Bh
    85h: 00h
    86h: 00h
    87h: 00h
    88h: 00h
    89h: 00h
    8Ah: 00h
    8Bh: 00h
    8Ch: 00h
    8Dh: 00h
    8Eh: 00h
    8Fh: 00h
    90h: 20h
    91h: D6h
    92h: CFh
    93h: 4Fh
    94h: 51h
    95h: 00h
    96h: 00h
    97h: 00h
    98h: B3h
    99h: 92h
    9Ah: 46h
    9Bh: CFh
    9Ch: 42h
    9Dh: 41h
    9Eh: 40h
    9Fh: CAh
    A0h: 13h
    A1h: 00h
    A2h: 00h
    A3h: 00h
    A4h: 00h
    A5h: 00h
    A6h: 00h
    A7h: 00h
    A8h: 00h
    A9h: 00h
    AAh: 00h
    ABh: 00h
    ACh: 00h
    ADh: 00h
    AEh: 00h
    AFh: 00h
    B0h: 00h
    B1h: 00h
    B2h: 00h
    B3h: 00h
    B4h: 00h
    B5h: 00h
    B6h: 00h
    B7h: 00h
    B8h: 00h
    B9h: 00h
    BAh: 00h
    BBh: 00h
    BCh: 00h
    BDh: 00h
    BEh: 00h
    BFh: 00h
    C0h: 00h
    C1h: 00h
    C2h: 80h
    C3h: 01h
    C4h: 3Ah
    C5h: 80h
    C6h: 00h
    C7h: 68h
    C8h: C0h
    C9h: 00h
    CAh: 00h
    CBh: 00h
    CCh: 00h
    CDh: 00h
    CEh: 00h
    CFh: 00h
    D0h: 00h
    D1h: 00h
    D2h: 00h
    D3h: 00h
    D4h: 00h
    D5h: 00h
    D6h: 00h
    D7h: 00h
    D8h: 00h
    D9h: 00h
    DAh: 00h
    DBh: 00h
    DCh: 00h
    DDh: 00h
    DEh: 00h
    DFh: 00h
    E0h: 00h
    E1h: 00h
    E2h: 80h
    E3h: 01h
    E4h: 2Ah
    E5h: B8h
    E6h: 00h
    E7h: 00h
    E8h: 00h
    E9h: 00h
    EAh: 00h
    EBh: 00h
    ECh: 00h
    EDh: 00h
    EEh: 00h
    EFh: 00h
    F0h: 5Fh
    F1h: 55h
    F2h: 48h
    F3h: 39h
    F4h: 34 h
    F5h: 37h
    F6h: 00h
    F7h: 00h
    F8h: 00h
    F9h: 00h
    FAh: 00h
    FBh: 00h
    FCh: 00h
    FDh: 00h
    FEh: 00h
    FFh: 00h

    Should the LF pin respond with this setting?

    thanks.

  • 0 in reply to choi jeongho
    TI__Mastermind 30515 points

    Hi Choi,

    From your reg. of UH947, it doesn't have some issues here. How about the UB948's board? Please check the LOCK pin, does it have toggled issue? if yes, it is link connection issue. what is the cable in your case? if it is STQ cable, you can try dual FPD-Link test. it should be ok.

    best regards,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    Prodigy 160 points

    Hi steven,

    I checked the LOCK pin but it doesn't toggle it.

    I changed the chip from DS90UH947 to DS90UB947. And tested. All settings are the same, only the chip was changed to DS90UB947.

    Since then, all issues have been resolved. LF PIN signal is also output normally, and flickering symptom disappears. As I changed the pixel clock frequency, I saw that the level of the LF PIN also changed.

    The same test was done with five boards. All boards were operating normally.

    As a result of this, there seems to be no problem with the board.

    I think there is a difference between the DS90UH947 and DS90UB947. Are there any differences except HDCP? I have no idea how to solve this problem.

    I must use the DS90UH947. Please help.

    best regards,

  • 0 in reply to choi jeongho
    TI__Mastermind 30515 points

    Choi,

    The UH947 has same feature and design as UB947 if the HDCP is not enabled. For your issue, if your UH947 chip has issue you can check the LOT number in the top of UH947? also, what is the part number in your test, is it UH948?

    best regards,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    Prodigy 160 points

    Hi, Steven

    I have attached a photo of the DS90UH947 parts I am using. Please check.

    And I used UH948 as the chip used in the test.

    best regards,

  • 0 in reply to choi jeongho
    TI__Mastermind 30515 points

    Choi,

    it sounds this sample is not good. For TI, the P in the "PUH" means this is one engineering sampling NOT released to market. Also the manufacture time is 2014yr. Please try to get the new released UH947 devices from your distributor.

    best regards,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    Prodigy 160 points

    Hi Steven

    I purchased a DS90UH947 part and tested it. The LF PIN works fine, and most boards have solved the problem.

    Thank you.

    best regards,