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Original question:

ADC32J25: JESD204B Configuration

ADC32J25: ADC32J25: JESD204B Configuration (Part 2)

Andrew Baek
Intellectual 915 points
Part Number: ADC32J25
Other Parts Discussed in Thread: LMK04828,

Hello,

I'm including the previous thread here for background.

ADC32J25: JESD204B Configuration - Data converters forum - Data converters - TI E2E support forums

Also attached are

  1. TICS Pro file for LMK04828
  2. Schematic 
    1. LMK04828 circuit is on Sheet 18
    2. ADC32J25 circuit is on Sheet 15
  3. Photos of SYSREF outputs
    1. SDCLKOUT1_sysref.jpg: sysref signal that goes to the FPGA
    2. SDCLKOUT3_sysref.jpg: sysref signal that goes to the ADC
  4. FPGA capture
    1. the waveform is continuous for 32 samples and goes thru a jump
    2. F=2 and K=32.  Is there any conflict with SYSREF = 8 MHz (20x_?

Issues

  • SDCLKOUT3 looks like a constant voltage at 2 volts.  There is no 8MHz sysref observed.
  • SDCLKOUT1: I changed  to 0x139[1:0] = 00 from 11 but the sysref is still repetitive at 8MHz.

We have verified sending the commands to the ADC and the FPGA is working.

  • We can read back the ADC commands.  We can make changes and the read back shows correctly
  • LMK04828: DCLKOUT12 and SDCLKOUT13 are brought out to MMCX connectors for monitoring purpose.  We can change the frequency from 160 MHz to 10 MHz or other frequency.

Could you advise on the issues with the SYSREF?

  • no clock/pulse on SDCLKOUT1
  • not being able to change to one-time on SDCLKOUT3)

Regards,

Andrew

tics_pro_v090823a.tcs

8625.fibersense_v1p23.pdf

  • 0
    TI__Mastermind 29542 points

    Hi Andrew,
    To test your config I will need to rework EVM given input isn't supported by onboard VCXO. 

    I'll update you accordingly. 

    Regards, 

    Vicente 

  • 0 in reply to vicente flores prado
    TI__Mastermind 29542 points

    Hi Andrew, 
    I was able to successfully see a continuous 8 MHz SYSREF output on SDCLKOUT1 & SDCLKOUT3 using config you provided after reworking LMK04828EVM. 

    I also changed SYSREF mode Pulser Mode: This results in SYSREF_ MUX (R313) = SYSREF PULSER (0x02) & SYNC_MODE = SYNC Pin (Pulser)

    You must also set SYSREF_PULSR_PD from H -> L 

    I set SYSREF_PULSE_CNT = 1 and observed a single pulse for both SDCLKOUT1/3 every time I clicked "send pulses" button in TICSpro GUI. 

    From schematic please note 100 ohm differential termination should be near Tx side before AC coupling caps. 

    One question - what is purpose of these 75 Ohm Resistors? 

    Regards, 

    Vicente

  • 0 in reply to vicente flores prado
    Intellectual 915 points

    HI Vicente,

    Would you review the .tcs attached here?

    I am still getting the continuous sysref.

    As for 75R, I'm also trying to track down the rationale.

    Thanks again for your support

    Regards,

    Andrew

    tics_pro_v092523b.tcs

  • 0 in reply to Andrew Baek
    TI__Genius 10995 points

    Hello Andrew,

    After loading the .tcs file you attached (attached below), the SYSREF_MUX is still set to continuous, which is why you are still seeing a continuous 8-MHz SYSREF signal.

    To change it, select the value of 0x139[0:1] to your desired SYSREF_MUX state. Note that the SYSREF_MUX state is the type of SYNC signal that you want to pass that resets your dividers and phase aligns your outputs.

    Let me know if I have missed any other questions you have.

    Good luck,

    Andrea

  • 0 in reply to Andrea Vallenilla
    Intellectual 915 points

    Hi Andrea,

    Can you load the attached tcs file below?

    It does clearly shows SYSREF Pulser.

    And the exported register shows 0x013902.

    However, the SYSREF received by the FPGA is still continuous.

    Is there another register that needs to be set to enable the pulse sysref?

    Regards,

    Andrew

    tics_pro_v092623a.tcs

    Fullscreen pll_regi_092623b.txt Download 
    R0 (INIT)	0x000090
R0	0x000010
R2	0x000200
R3	0x000306
R4	0x0004D0
R5	0x00055B
R6	0x000600
R12	0x000C51
R13	0x000D04
R256	0x01000F
R257	0x010155
R258	0x010255
R259	0x010301
R260	0x010422
R261	0x010500
R262	0x010670
R263	0x010711
R264	0x01080F
R265	0x010955
R266	0x010A55
R267	0x010B00
R268	0x010C22
R269	0x010D00
R270	0x010E70
R271	0x010F66
R272	0x01100F
R273	0x011155
R274	0x011255
R275	0x011300
R276	0x011402
R277	0x011500
R278	0x0116F0
R279	0x011711
R280	0x01180F
R281	0x011955
R282	0x011A55
R283	0x011B00
R284	0x011C02
R285	0x011D00
R286	0x011EF0
R287	0x011F17
R288	0x012018
R289	0x012155
R290	0x012255
R291	0x012300
R292	0x012402
R293	0x012500
R294	0x0126F1
R295	0x012711
R296	0x012808
R297	0x012955
R298	0x012A55
R299	0x012B00
R300	0x012C02
R301	0x012D00
R302	0x012EF9
R303	0x012F00
R304	0x01300F
R305	0x013155
R306	0x013255
R307	0x013300
R308	0x013422
R309	0x013500
R310	0x0136F0
R311	0x013766
R312	0x013805
R313	0x013902
R314	0x013A01
R315	0x013BE0
R316	0x013C00
R317	0x013D08
R318	0x013E00
R319	0x013F00
R320	0x014000
R321	0x014101
R322	0x014200
R323	0x014311
R324	0x0144FF
R325	0x01457F
R326	0x014600
R327	0x01471A
R328	0x014802
R329	0x014942
R330	0x014A02
R331	0x014B16
R332	0x014C00
R333	0x014D00
R334	0x014EC0
R335	0x014F7F
R336	0x015003
R337	0x015102
R338	0x015200
R339	0x015300
R340	0x015478
R341	0x015500
R342	0x015664
R343	0x015700
R344	0x015896
R345	0x015900
R346	0x015A64
R347	0x015BD4
R348	0x015C20
R349	0x015D00
R350	0x015E00
R351	0x015F0B
R352	0x016000
R353	0x016101
R354	0x016225
R355	0x016300
R356	0x016400
R357	0x01650F
R369	0x0171AA
R370	0x017202
R380	0x017C15
R381	0x017D33
R358	0x016600
R359	0x016700
R360	0x01680F
R361	0x016959
R362	0x016A20
R363	0x016B00
R364	0x016C00
R365	0x016D00
R366	0x016E13
R371	0x017300
R386	0x018200
R387	0x018300
R388	0x018400
R389	0x018500
R392	0x018800
R393	0x018900
R394	0x018A00
R395	0x018B00
R8189	0x1FFD00
R8190	0x1FFE00
R8191	0x1FFF53

  • 0 in reply to Andrew Baek
    Intellectual 915 points

    Hi Andrea,

    What voltage type should be used for the ADCCLK and SYSREF?

    The ADC also has AC caps and 100 Ohm across the P/N pins.

    Initially I used LCPECL on both but SYSREF did not show a signal.  

    So updated to LVDS and can observe the SYSREF showed the correct clock frequency (5 MHz in the particular case).

    Regards,

    Andrew

  • 0 in reply to Andrew Baek
    TI__Genius 10995 points

    Hello Andrew,

    I downloaded your newest file and that one did show SYSREF Pulser.

    Andrew Baek said:
    Is there another register that needs to be set to enable the pulse sysref?

    Yes, I just realized you were setting the SYNC_MODE register incorrectly. Set register 0x143 = 13. This allows you to get the pulser signal from the SYNC SPI command. I have attached this .tcs file below (sorry for not attaching the one I used yesterday to that reply).

    4828_SYSREF_Pulser.tcs

    If you want to obtain the pulser signal from the SYNC Pin, then set 0x143 = 12.

    Andrew Baek said:
    What voltage type should be used for the ADCCLK and SYSREF?

    The common mode voltage of the ADC32J25 is 0.95-V with the below amplitudes for each clock format. In general, ADCs can accept LVDS, LVPECL, and CML from TI's clocking devices.

    Andrew Baek said:
    So updated to LVDS and can observe the SYSREF showed the correct clock frequency (5 MHz in the particular case).

    LVDS is an accepted signal to the ADC based on it's swing characteristics, so using LVDS will work. However, form the picture above, you have terminated the LMK outputs as LVPECL outputs. I would suggest to change the SYSREF outputs to LVPECL, and if you still encounter a problem, make sure to have any LVDS outputs from the LMK to match the following topology:

    Hope this helps and let me know if you need anything else.

    Good luck,

    Andrea

  • 0 in reply to Andrea Vallenilla
    Intellectual 915 points

    Hi Andrea,

    The SYSREFs are still continous.

    Could you take a look at the attached .tcs?

    Regards,

    Andrewtics_pro_v092723a.tcs

  • 0 in reply to Andrew Baek
    TI__Genius 10995 points

    Hello Andrew,

    I was able to get the Pulser mode with your same config except setting 0x143 = 13 to set the pulser in to be sent via SPI (which is the mode I prefer), is there a reason why you are using the SYNC Pin? Also, to sent the pulses via SPI, all you need is to send the command 0x13E = 0 and the pulse(s) should be sent. Please find the waveform I saw on the scope below and the config I used:

    4828_SYSREF_Pulser_9-28.tcs

    Let me know if you have any other questions.

    Good luck,

    Andrea