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URGENT: getting started with LMX2492EVM, no output

Babu Devnarayan Choudhary
Prodigy 150 points
Other Parts Discussed in Thread: LMX2492, LMX2492EVM, CODELOADER, USB2ANY

Hello,

I have recently purchased following LMX2492 evaluation board from TI, and want to get going with it quickly.

I am thoroughly following this user guide and the youtube video.

I couldn't figure out what is the Red-Probe in the video. But by close watch, it seems to be supply to Trig1, so I connected Trig1 to 5V. As per guide, this is not required, but I imagined it could be trigger. After all possible efforts,  I couldn't make it work. I don't see any output on oscilloscope. Even if my oscilloscope is not able to sample directly at RF frequency (samples upto 1 GPS ),  I believe I should see some output atleast.I am using CodeLoader for programming it as described.

Best Regards,

Babu Devnarayan

  • 0
    TI__Expert 4085 points

    Hi Babu,

    Please look at this post:

    By default, it doesn't seem the on-board XO is receiving power. Without the on-board XO you will not get an output.

    Please populate the resistors R21 and R28 with the values indicated on the User's Guide Schematic, to power the XO.

    The red probe seems to be connected to TRIG1 Test point.

    Best Regards,

    Julian

    If my post answers your question, please click on "Verify Answer" button.

  • 0 in reply to Julian Di Matteo
    Prodigy 150 points

    Hi Julian,

    Thanks a lot...I have soldered SMD resisters R21 = 18ohm and R28 = 10ohm, and oscillator seems to be up now as I can see 100MHz output from Oscin Pin. However, still I don't see any output on RFout, RFout/2 or RFout/4 except some apparent noise. 

    What's missing ?

    I am using this oscilloscope -Picotech 5444B

    https://www.picotech.com/oscilloscope/5000/flexible-resolution-oscilloscope

  • 0 in reply to Babu Devnarayan Choudhary
    TI__Expert 4085 points

    Hi Babu,

    When you pre Ctrl+L to program the device, do you see a small change in current coming from the power supply? if so it's likely that the device is being programmed.

    Also did you set your scope termination to 50 ohm?

    Thanks,

    Julian

    If my post answers your question, please click on "Verify Answer" button.

  • 0 in reply to Julian Di Matteo
    TI__Expert 4085 points

    Hi Babu,

    Also please provide a screenshot of the PLL tab settings in code loader and the bits/pins tab. Please go to the registers tab please export the register settings into a text file and attach it.

    Thanks,

    Julian

    If my post answers your question, please click on "Verify Answer" button.

  • 0 in reply to Julian Di Matteo
    Prodigy 150 points
    Hi Julian,

    Thanks a lot. I have left office before your message arrived...so I will try your suggestions tomorrow. Can we do a Skype tomorrow to sort this out, because I have wasted whole day on this...and thinking of waiting for 1 more day for this is killing me due to time constraint.

    Best Regards,

    Babu
  • 0 in reply to Babu Devnarayan Choudhary
    TI__Expert 4085 points

    Does your scope have enough bandwidth for this?

    By default RFout/4 is turned off. Look at the schematic on the LMX2492 User's guide. Switch L5p to l5 to enable it.

    In default code loader settings VCO frequency is 9600 MHz. So RFout=9600MHz and RFout/2=4800MHz.

    Again, just provide your code loader configuration tomorrow.

    Thanks,

    Julian

  • 0 in reply to Julian Di Matteo
    Prodigy 150 points
    Hi Julian,

    My scope picotech 5444B got 200 MHz bandwidth with max 1GSPS (10 GSPS in ETS mode).

    Even if it does not have enough bandwidth to capture the signal...it should show some distorted signal, which should change when changing PLL settings....but right now it doesn't show any output.
  • 0 in reply to Babu Devnarayan Choudhary
    Prodigy 150 points

    Hi Julian,

    When you pre Ctrl+L to program the device, do you see a small change in current coming from the power supply? if so it's likely that the device is being programmed.

    YES, It increases from 0.20Amp to 0.23Amp

    Also did you set your scope termination to 50 ohm?

    My Scope doesn't have any feature like that, I am simply putting probes into RF ports of the board.

    I am attaching other things.

    Register.txt 
    R141	0x008D00
R140	0x008C00
R139	0x008B00
R138	0x008A00
R137	0x008900
R136	0x008800
R135	0x008700
R134	0x008600
R133	0x008500
R132	0x008400
R131	0x008300
R130	0x008200
R129	0x008100
R128	0x008000
R127	0x007F00
R126	0x007E00
R125	0x007D00
R124	0x007C00
R123	0x007B00
R122	0x007A00
R121	0x007900
R120	0x007800
R119	0x007700
R118	0x007600
R117	0x007500
R116	0x007400
R115	0x007300
R114	0x007200
R113	0x007100
R112	0x007000
R111	0x006F00
R110	0x006E00
R109	0x006D00
R108	0x006C00
R107	0x006B00
R106	0x006A00
R105	0x006900
R104	0x006800
R103	0x006700
R102	0x006600
R101	0x006500
R100	0x006400
R99	0x006300
R98	0x006200
R97	0x006100
R96	0x006000
R95	0x005F00
R94	0x005E00
R93	0x005D00
R92	0x005C00
R91	0x005B00
R90	0x005A00
R89	0x005900
R88	0x005800
R87	0x005700
R86	0x005600
R85	0x005500
R84	0x005400
R83	0x005300
R82	0x005200
R81	0x005100
R80	0x005000
R79	0x004F00
R78	0x004E00
R77	0x004D00
R76	0x004C00
R75	0x004B00
R74	0x004A00
R73	0x004900
R72	0x004800
R71	0x004700
R70	0x004600
R69	0x004500
R68	0x004400
R67	0x004300
R66	0x004200
R65	0x004100
R64	0x004000
R63	0x003F00
R62	0x003E00
R61	0x003D00
R60	0x003C00
R59	0x003B00
R58	0x003A00
R57	0x003900
R56	0x00380F
R55	0x00376F
R54	0x00366F
R53	0x00350F
R52	0x00348F
R51	0x00330F
R50	0x00320F
R49	0x0031AF
R48	0x00300F
R47	0x002F4F
R46	0x002E30
R45	0x002D00
R44	0x002C00
R43	0x002B00
R42	0x002A00
R41	0x002900
R40	0x002800
R39	0x002752
R38	0x002618
R37	0x002510
R36	0x002408
R35	0x002341
R34	0x002204
R33	0x002120
R32	0x002000
R31	0x001F2E
R30	0x001E04
R29	0x001D00
R28	0x001C1F
R27	0x001B08
R26	0x001A00
R25	0x001901
R24	0x001800
R23	0x001703
R22	0x0016E8
R21	0x001500
R20	0x001400
R19	0x001300
R18	0x00122C
R17	0x001100
R16	0x001060
R15	0x000F00
R14	0x000E00
R13	0x000D00
R12	0x000C00
R11	0x000B00
R10	0x000A00
R9	0x000900
R8	0x000800
R7	0x000700
R6	0x000600
R5	0x000500
R4	0x000400
R3	0x000300
R2	0x000201
R1	0x000100
R0	0x000018

    Also, here is one more thing I figured out. After launching Code Loader, I see spikes amidst noise like this...if I close it, spikes disappear.

    This may be genuine signal from PLL but this doesn't change at all when I change PLL settings...which makes me believe this isn't

  • 0 in reply to Babu Devnarayan Choudhary
    Prodigy 150 points
    Hi Julian,

    I have been eagerly waiting for your response...I want to sort this out today before leaving for home in 30min. Can we have a call please.

    Thanks a lot in advance.
  • 0 in reply to Babu Devnarayan Choudhary
    TI__Mastermind 27581 points
    Babu,

    I am sorry that you are having issues getting this board running, but I do not think that the board is defective. I recently posted a blog at (e2e.ti.com/.../what-to-do-when-your-pll-does-not-lock) that goes into a systematic debugging process that is good for our boards.

    For the LMX2492, the VCO draws a lot of current (about 200-250 mA) and the LMX2492 itself draws somewhere in the ballpark of 40 mA. So if you change the POWERDOWN word, you will likely see a change on the order of 40 mA or so.

    The board has many components and options, but not all components are placed. For instance, the 100 MHz XO is on the board to be available to experiment with, but the default is not hooked up or powered on. This is to allow a higher quality external signal source to be used.

    There is a 100 MHz XO on the board, but the power to this is disconnected; this allows a higher quality reference to be used.

    For instuctions, rely on the EVM instructions at (www.ti.com/.../snau160d.pdf), specifically the figure 2.1 that shows the required hookup. I saw some mention of using an oscilloscope to see the output of the VCO, but it is unlikely to see it as the output is 9.8 GHz, or 4.9 GHz with divide by 2. As mentioned already, divide by 4 is disabled. Maybe you can see the 100 MHz XO (as it looks like you ahve hooked it up), but you could also look at the tuning voltage of the VCO as well.

    As for the red wire, this is for triggering purposes for the ramping feature. But right now, it seems that you are having issues getting the part to lock, so don't get distracted by this. The connections are 5V supply to the SMA and normally would need 100 MHz input, but it seems that you have connected that already.

    REgards,
    Dean
  • 0 in reply to Dean Banerjee
    Prodigy 150 points

    Hello Dean,

    Thanks a lot for your detailed response. I also figured out that there is not active filter on board...amplifiers are missing.

    I will send you snaps,  but  I believe you might be  aware about it. I connected oscilloscope to charge pump output but no change. I suspect communication between us baby and PLL as well.

  • 0 in reply to Dean Banerjee
    Prodigy 150 points
    Hello Dean,

    Thanks a lot for your detailed response. Just to point, both the links you referred do not exist, but I have figured them out correctly at following locations...

    e2e.ti.com/.../what-to-do-when-your-pll-does-not-lock

    www.ti.com/.../snau160d.pdf


    What I have figured out while tracing the cause on my own is that, the board does not have components of the active filter populated....I don't see op-amp as detailed in the schematic. This is completely contrary to expectations...as it as many more components not-populated as per schematic, it's quite hard to figure out what is essential and what is optional in order to make it working.

    Also, I tried tapping charge-pump output on oscilloscope, but it doesn't change at all when I change the configuration using Code-Loader...so I suspect the communication between USB2ANY and the board as well.

    I have ordered this board believing a ready-to-go solution, and we don't have SMD soldering facilities for the missing stuffs.

    Is there a possibility of shipping a fully functional board ?

    Best Regards,

    Babu
  • 0 in reply to Babu Devnarayan Choudhary
    TI__Expert 4085 points

    Hi Babu,

    I'm sorry you are having trouble getting started with this board.

    Here is a picture of the LMX2492EVM that I use, which I ordered from ti.com.

    As you can see there are some components that are in the schematic but are not placed in the board because they are optional, or are for user configuration as Dean explained earlier. 

    The only modification I did to this board was to place the two resistors(R28 &R21) to connect and power the on-board XO and I was able to get an output.

    From your codeloader tab it seems that your PC recognizes the USB2ANY. You mentioned when you pressed CTRL+L you noticed the current changed. 

    That means that you are communicating with the device. As Dean mentioned, when you go into the bits/pins tab, and change it from "powered up" to "powered down" do you see a change in the current supplied from the power supply?

    Also I believe for 4.8GHz and 9.6GHz a spectrum analyzer would be better. Do you have access to one?

    Thanks,

    Julian

  • 0 in reply to Julian Di Matteo
    Prodigy 150 points

    Hi Julian,

    Thanks a lot...still no luck. I do have a spectrum analyzer HyperLOG 7040 from Aaronia, but it covers 700MHz to 4GHz only.

    What's the way to enable RF/4 to see something.

    Also, I am puzzled where are filter components on the board...it seems Op-Amp of the filter and some 0ohm bridging resistors   R3aLF, R55 are missing. If that is true, expecting output on VCO terminals is madness. But I tried to tap onto CPOUT as well on TP_vtune, it shows some DC signal on oscilloscope, but don't show any change when changing PLL settings....frequency change, ramping etc.

     

    Best Regards,

    Babu

  • 0 in reply to Babu Devnarayan Choudhary
    Prodigy 150 points
    Hi Julian,

    I ordered one replacement board of same PLL from mouser believing that current board might be faulty....but have not opened it yet as suggested by mouser. If you believe current board is faulty, I can open the new one and do the same testing on that.

    Best Regards,

    Babu
  • 0 in reply to Babu Devnarayan Choudhary
    Prodigy 150 points
    Hi Julian,

    In order to enable RF/4, I have unsoldered L5p, and soldered at L5 as mentioned in the datasheet. Also, I have made soldered 0ohm connections in place of R55 and R3aLF as active filter part of the board seemed to be disconnected to me from the PLL.

    Despite all this effort, I don't see any output on my Spectrometer, which covers the range of RF/4 adequately (700MHz to 4GHz)....I have exhausted all the options now.

    What do you suggest ???

    Best Regards,

    Babu
  • 0 in reply to Babu Devnarayan Choudhary
    TI__Mastermind 27581 points

    Babu,

    Have you first tried to get the board working in the default configuration?   By changing the board, this adds more degrees freedom for things to go wrong.   Also you might find this blog I wrote on getting the PLL to lock useful:

    https://e2e.ti.com/blogs_/b/analogwire/archive/2016/07/12/what-to-do-when-your-pll-does-not-lock

    In the case here, changing the inductor L5 should create an ouptut around 2.4 GHz at the RF/4 output and the span you have should be wide enough to see it, regardless of if the PLL is locked or not.   The VCO on this board consumes on the order of 40 mA and the VCO is about 250 mA, so you would see the current of the VCO if it is running.

    For the active filter, you need to also disconnect R3_LF and also ensure that power is to the op amp supply.  Ensure that R54 and R36 are placed.

    Regards,
    Dean

    Lik

  • 0 in reply to Dean Banerjee
    Prodigy 150 points

    Hi Dean,

    Could you precisely tell me following. Where is the Op Amp chip on the board ?...I see empty slot in place of it, please see in the pics I posted in earlier post.

    Where is R36 which you are referring ?

    I had high opinion of TI in terms of products but it has been big disappointment this time. Why all the wiring things one after other I am being told, not part of the datasheet...this is annoying me as I have wasted several weeks just in getting started, which should be a straight forward thing.

    Could you ship me a fully tested board...I can ship back mine one to you.

    Best Regards,

    Babu