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LMK04828: about Direct SYSREF distribution

user5983069
Intellectual 320 points
Part Number: LMK04828
Other Parts Discussed in Thread: LMK04803,

Hello

Now I try to "direct sysref mode" but It doesnt work (no output and signal fixed to LOW . input SYNC signal is High.)

My Configuration is as below. (SYSREF signal is conected  to Clkin0 )

0x143   0x10    SYNC_MODE

0x139   0x04     SYSREF_MUX,SYSREF CLKin0_MUX

0x147   0x18    CLKin0_OUT_MUX

0x104   0x20    SDCLKoutY_DDLY

0x140   0x07    SYSREF_DDLY_PD,PLSR,PD

0x106   0x30   SDCLKoutY_PD

0x107  0x55    SDCLKoutY_FMT

Would you please tell me something wrong point?

Takeshi

  • 0
    TI__Mastermind 28530 points

    Hello Takeshi-san,

    Do you have a full .tcs file or programming I could load?  I could confirm tomorrow.

    73,
    Timothy

  • 0 in reply to Timothy T
    Intellectual 320 points

    Hello Timothy

    I dont have tcs file . Full programming is below.

    0X0000 0X0080
    0X0000 0X0000
    0X0002 0X0000
    0X0100 0X0004
    0X0101 0X0056
    0X0103 0X0000
    0X0104 0X0020
    0X0105 0X0000
    0X0106 0X0030
    0X0107 0X0055
    0X0108 0X000A
    0X0109 0X0056
    0X010B 0X0000
    0X010C 0X0020
    0X010D 0X0000
    0X010E 0X00F1
    0X010F 0X0011
    0X0110 0X0004
    0X0111 0X0056
    0X0113 0X0000
    0X0114 0X0020
    0X0115 0X0000
    0X0116 0X00F0
    0X0117 0X0055
    0X0118 0X0010
    0X0119 0X0055
    0X011B 0X0000
    0X011C 0X0020
    0X011D 0X0000
    0X011E 0X00F0
    0X011F 0X0011
    0X0120 0X000A
    0X0121 0X0089
    0X0123 0X0000
    0X0124 0X0020
    0X0125 0X0000
    0X0126 0X00F0
    0X0127 0X0011
    0X0128 0X000A
    0X0129 0X0056
    0X012B 0X0000
    0X012C 0X0020
    0X012D 0X0000
    0X012E 0X00F0
    0X012F 0X0011
    0X0130 0X0004
    0X0131 0X0089
    0X0133 0X0000
    0X0134 0X0020
    0X0135 0X0000
    0X0136 0X00F0
    0X0137 0X0055
    0X0138 0X0005
    0X0139 0X0004
    0X013A 0X0005
    0X013B 0X0000
    0X013C 0X0000
    0X013D 0X0008
    0X013E 0X0000
    0X013F 0X0000
    0X0140 0X0007
    0X0141 0X0000
    0X0142 0X0000
    0X0143 0X0010
    0X0144 0X0000
    0X0145 0X007F
    0X0146 0X0008
    0X0147 0X0018
    0X0148 0X0033
    0X0149 0X0033
    0X014A 0X0002
    0X014B 0X0002
    0X014C 0X0000
    0X014D 0X0000
    0X014E 0X0000
    0X014F 0X007F
    0X0150 0X0000
    0X0151 0X0002
    0X0152 0X0000
    0X0153 0X0000
    0X0154 0X0005
    0X0155 0X0000
    0X0156 0X0005
    0X0157 0X0000
    0X0158 0X0096
    0X0159 0X0000
    0X015A 0X0001
    0X015B 0X00DF
    0X015C 0X0008
    0X015D 0X0099
    0X015E 0X0000
    0X015F 0X000B
    0X0160 0X0000
    0X0161 0X0001
    0X0162 0X00A0
    0X0163 0X0000
    0X0164 0X0000
    0X0165 0X000C
    0X0171 0X00AA
    0X0172 0X0002
    0X017C 0X0015
    0X017D 0X0033
    0X0166 0X0000
    0X0167 0X0000
    0X0168 0X0010
    0X0169 0X0059
    0X016A 0X0020
    0X016B 0X0000
    0X016C 0X0000
    0X016D 0X0000
    0X016E 0X0013
    0X0173 0X0000

    Takeshi 

  • 0 in reply to user5983069
    TI__Mastermind 28530 points

    Hello Takeshi-san,

    Thank-you for the full programming.  I was able to confirm operation.  The settings you are using appear correct.

    Can you please check that pin 5, the reset pin is in a LOW state.  If the device is held in reset, then your programming wouldn't take effect.

       - Have you been able to confirm programming?  You could do this by toggling the POWERDOWN bit R2[0] to 1, if device current reduces then programming is working.  You could also toggle the polarity of the output PLL1_LD or PLL2_LD pin by using the PLLx_LD_TYPE to toggle to an output inverted setting to confirm those pins respond to the inversion.

    If further investigation is needed, can you share your schematic?  What is the schematic of your input to CLKin0?  What type of signal are you providing to CLKin0?

    73,
    Timothy

  • 0 in reply to Timothy T
    Intellectual 320 points

    Hello Timothy

    I checked that pin 5 is  in a LOW state. And another 614MHz CLK is outputted so no reset state.

    I input LVDS(output from LMK04803 and 100Ω terminated and AC coupled) signal to CLKin0 . input voltage Vpp is 844mV measured at Device pin.

    Frequency is 1.92MHz.

    Takeshi

  • 0 in reply to user5983069
    Intellectual 320 points

    Hello Timothy

    Sorry I checked output SYSREF signal again and it was outputted  .

    But output frequency is 10 Hz,1KHz,,,not stable..

    When I stopped SYSREF Which is inputed Clkin0 ,still SYSREF is outputted .

    so it doesnt works.

    .

  • 0 in reply to user5983069
    TI__Mastermind 28530 points

    Hello Takeshi-san,

    How many boards have you tested this on?

    Can you confirm 3.3 V at each Vcc pin?

    73,
    Timothy

  • 0 in reply to Timothy T
    Intellectual 320 points

    Hello Timothy

    I checked 2 devices and confirmed that all Vcc pin is3.3V.

    Takeshi

  • 0 in reply to user5983069
    TI__Mastermind 28530 points

    Hello Takeshi-san,

    Can you share the schematic?  Particularly the CLKin0 section?

    You mention getting getting some output when no CLKin0 is driven.  I presume you are AC coupling and there is no 100 ohm resistor on the IC side of the CLKin0?  Change the input type to (CLKin0_TYPE = 1: MOS).  This is register 0x146[0] = 1.

    73,
    Timothy

  • 0 in reply to Timothy T
    Intellectual 320 points

    Hello Timothy

    I added schematics.  I changed input signal and CLOCKin0_TYPE =1,but  sysref was not outputted.(see. schematic 2)

    In Schematic.3  I could output SYSREF.

    When I didnt input SYSREF signal inSchematic 3  CLKin0 pin,sysref was not outputted ,so Direct sysref distribution function  works.

     The diffrence between Schematic 1 and 3 is using PLL1 or not.

    Are there some conditions to stop output SYSREF?? for example if pll1 is unlocked,then stopping output sysref or etc...?

    I add configuration for Schematic3 below.

    Takeshi 

    0 0X0000 0X0080
    0 0X0000 0X0000
    0 0X0002 0X0000
    0 0X0100 0X000A
    0 0X0101 0X0023
    0 0X0103 0X0000
    0 0X0104 0X0020
    0 0X0105 0X0000
    0 0X0106 0X0030
    0 0X0107 0X0011
    0 0X0108 0X0004
    0 0X0109 0X0023
    0 0X010B 0X0000
    0 0X010C 0X0020
    0 0X010D 0X0000
    0 0X010E 0X00F0
    0 0X010F 0X0055
    0 0X0110 0X0004
    0 0X0111 0X0023
    0 0X0113 0X0000
    0 0X0114 0X0020
    0 0X0115 0X0000
    0 0X0116 0X00F0
    0 0X0117 0X0055
    0 0X0118 0X000A
    0 0X0119 0X0023
    0 0X011B 0X0000
    0 0X011C 0X0020
    0 0X011D 0X0000
    0 0X011E 0X00F0
    0 0X011F 0X0011
    0 0X0120 0X0008
    0 0X0121 0X0045
    0 0X0123 0X0000
    0 0X0124 0X0020
    0 0X0125 0X0000
    0 0X0126 0X00F0
    0 0X0127 0X0011
    0 0X0128 0X0004
    0 0X0129 0X0045
    0 0X012B 0X0000
    0 0X012C 0X0020
    0 0X012D 0X0000
    0 0X012E 0X00F0
    0 0X012F 0X0055
    0 0X0130 0X000A
    0 0X0131 0X0045
    0 0X0133 0X0000
    0 0X0134 0X0020
    0 0X0135 0X0000
    0 0X0136 0X00F0
    0 0X0137 0X0011
    0 0X0138 0X0005
    0 0X0139 0X0004
    0 0X013A 0X0005
    0 0X013B 0X0000
    0 0X013C 0X0000
    0 0X013D 0X0008
    0 0X013E 0X0000
    0 0X013F 0X0000
    0 0X0140 0X0007
    0 0X0141 0X0000
    0 0X0142 0X0000
    0 0X0143 0X0010
    0 0X0144 0X0000
    0 0X0145 0X007F
    0 0X0146 0X0008
    0 0X0147 0X0018
    0 0X0148 0X0033
    0 0X0149 0X0033
    0 0X014A 0X0002
    0 0X014B 0X0002
    0 0X014C 0X0000
    0 0X014D 0X0000
    0 0X014E 0X0000
    0 0X014F 0X007F
    0 0X0150 0X0000
    0 0X0151 0X0002
    0 0X0152 0X0000
    0 0X0153 0X0000
    0 0X0154 0X0005
    0 0X0155 0X0000
    0 0X0156 0X0005
    0 0X0157 0X0000
    0 0X0158 0X0096
    0 0X0159 0X0000
    0 0X015A 0X0001
    0 0X015B 0X00DF
    0 0X015C 0X0008
    0 0X015D 0X0099
    0 0X015E 0X0000
    0 0X015F 0X000B
    0 0X0160 0X0000
    0 0X0161 0X0001
    0 0X0162 0X00A0
    0 0X0163 0X0000
    0 0X0164 0X0000
    0 0X0165 0X000C
    0 0X0171 0X00AA
    0 0X0172 0X0002
    0 0X017C 0X0015
    0 0X017D 0X0033
    0 0X0166 0X0000
    0 0X0167 0X0000
    0 0X0168 0X0010
    0 0X0169 0X0059
    0 0X016A 0X0020
    0 0X016B 0X0000
    0 0X016C 0X0000
    0 0X016D 0X0000
    0 0X016E 0X0013
    0 0X0173 0X0000

  • 0 in reply to user5983069
    TI__Mastermind 28530 points

    Hello Takeshi-san,

    user5983069 said:
    I added schematics.  I changed input signal and CLOCKin0_TYPE =1,but  sysref was not outputted.(see. schematic 2)

    Note, it is acceptable to use the MOS mode with Schematic 1.  MOS mode has a larger (50 mV) threshold wwhich will prevent noise from oscillating the input buffer when no input is present.  This is important given the AC coupling to CLKin0.  It is recommended to use MOS mode for AC coupled inputs which may be turned off.  (As for LOS detect note).

    user5983069 said:
    In Schematic.3  I could output SYSREF.

    When SYSREF was output, this was a well behaved 1.92 MHz signal?  I am concerned your capacitors may be too small.

    There is no difference in your schematic 1 vs. schematic 3 which should change behavior.   PLL lock should not have an impact.  In my test neither PLL1 or PLL2 is locked.

    user5983069 said:
    When I didnt input SYSREF signal inSchematic 3  CLKin0 pin,sysref was not outputted ,so Direct sysref distribution function  works.

    user5983069 said:
    I add configuration for Schematic3 below.

    It appears this config is using bipolar input.  If you do not use MOS  mode and stop the signal, there is a risk that it may output noise.

    user5983069 said:
     The diffrence between Schematic 1 and 3 is using PLL1 or not.

    Are there some conditions to stop output SYSREF?? for example if pll1 is unlocked,then stopping output sysref or etc...?

    There are no conditions that would stop output of SYSREF.  There are bits to enable sync if PLL1 or PLL2 is unlocked, but SYSREF would not be impacted by these SYNC.

    --

    One suggestion I have is to use a higher value capacitor for CLKin0 AC coupling.  0.1 uF is quite small for 1.92 MHz.

  • 0 in reply to Timothy T
    Intellectual 320 points

    Hello  Timothy

    Im so Sorry.when I changed bipolar ⇒ mos , I changed   ClKin enable bit  as 0 too.that was my mistake,So,It works in Schematic 2.

    In schematic 1 it didnt work .Maybe the reason is input wave edge is not good by reflection.(there isnt figure in figure1, but I used 3  receive  (fanout 3 LM04828×1 FPGA×2))

    I  changed　input signal as CMOS and CLKin buffer type as mos then input wave was improved and  it works.Sysref output signal frequency is no problem.

    This circuit is tempolary ,so I will change LMK04803 to LMK04828 and SYSREF signal connect 1 on 1.

    And by your suggestion, I want to optimaize value of AC coupling capacitor .

    Do you have reccomend value?

    Takeshi  

  • 0 in reply to Timothy T
    Intellectual 320 points

    Hello Timothy

    Im so Sorry.when I changed bipolar ⇒ mos , I changed   ClKin enable bit  as 0 too.that was my mistake,So,It works in Schematic 2.


    In schematic 1 it didnt work .Maybe the reason is input wave edge is not good by reflection.(there isnt figure in figure1, but I used 3  receive  (fanout 3 LM04828×1 FPGA×2))

    I  changed　input signal as CMOS and CLKin buffer type as mos then input wave was improved and  it works.Sysref output signal frequency is no problem.

    This circuit is tempolary ,so I will change LMK04803 to LMK04828 and SYSREF signal connect 1 on 1.


    And by your suggestion, I want to optimaize value of AC coupling capacitor .

    Do you have reccomend value?

    Takeshi

  • 0 in reply to user5983069
    TI__Mastermind 28530 points

    Hello Takeshi-san,

    Yes, please confirm using one LVDS output to one LVDS input.  I expect it will work.

    As for needing a larger value capacitor.  I was examining my setup, the 0.1 uF is acceptable.  I was originally testing using a balun to convert a single ended signal to differential for testing.  The balun was causing my excessive droop, not the capacitors.

    73,
    Timothy