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LMX2492: Flat ramp

Jason Tandy
Prodigy 80 points
Part Number: LMX2492
Other Parts Discussed in Thread: CODELOADER

Dear Ti,

I am setting up a two ramp example, sweeping up and down in frequency.

Using code loader:

The second ramp stays at the same frequency rather than sweeping back to the start frequency.

I hit return in one of the parameters, with out changing the value and then it starts to work as expected.

Dumping the registers in both cases shows no difference in values.

What is happening?

I get this on the eval board.

On my board, I have not been able to get the second ramp to sweep.

I would upload the images, but can't get it to work in this window.

Thanks, Jason.

Thanks, Jason.

  • 0
    TI__Expert 5370 points
    Dear Jason,

    I would start by upgrading your software to TiCS PRO available on ti.com. It might be the root cause of your issue.

    Regards, Simon.
  • 0 in reply to Simon Damphousse
    Prodigy 80 points

    Thanks Simon,

    I will try that at some point.

    But I am seeing this on my own board, which does not use TI software, so I don't think it is just that.  Any other thoughts

    Regards, Jason.

    7536.flat top.pdf

  • 0 in reply to Jason Tandy
    TI__Mastermind 27851 points

    Jason,

    If I understand correctly, you get stuck on the last ramp and it doesn't repeat, but then you press enter and then it works on CodeLoader.  If this is the case, sounds like an update issue with CodeLoader.  Pressing enter programs a register, so perhaps what you were seeing on the ramp GUI on CodeLoader is not the same as what is on the registers.  TICSPro is much more elegant and much faster, especially for this ramp GUI.

    It sounds like you are also having issues with your software.  Assuming that you have the RAMPx_NEXT set up, the other thing to consider is the RAMP_EN bit.  The action of programming the RAMP_EN bit to 1 or programming the PLL_N value starts the ramp.  So the way it should be done is set up the ramp as it should be with RAMP_EN=0.  Then when everything is right, then set RAMP_EN=1.  Is it possible that you are setting up the ramp while RAMP_EN=1?

    Regards,
    Dean

  • 0 in reply to Dean Banerjee
    Prodigy 80 points

    Hi Dean,

    I have tried setting RAMP_EN to zero and then putting is back to a one, but the flat top is still there when it starts up again.  I am only changing this one register.

    So from power on,

    - I load the register set (R141 to R0) and get the flat top

    - RAMP_EN to zero

    - RAMP_EN to one

    flat top is still there.

    RAMPx_NEXT is set to '1' for RAMP0 and set to '0' for RAMP1.8078.flat top.pdf

    Regards, Jason.

  • 0 in reply to Jason Tandy
    TI__Mastermind 27851 points
    Jason,

    If I call the upward ramp "RAMP0" and the downward ramp "RAMP1" then it seems that in the non-desired flat top case is that RAMP0 is running as intended, but instead of RAMP1 downward ramping, it is not going at all. It is as if RAMP1_INC=0. Then when RAMP1 is finished, we see an abrupt correction back to the starting point of RAMP0, as would be the case if RAMP0_RST=1.

    I suspect that in CodeLoader, perhaps RAMP1 is not getting updated with teh gui until you press return.

    Regards,
    Dean
  • 0 in reply to Dean Banerjee
    Prodigy 80 points

    Dear Dean,

    I have found that CodeLoader is sending '0' data for the ramp increment and then correcting itself with a later set of transfers.  That explains the EVAL board behaviour.

    I still can't get the second ramp to ramp down on my board (I need the ramp down to improve the undershoot).

    Please see attached the register set being uploaded and a screen shot of the resultant wave form.  I may have changed the down ramp width by a single command in the screen shot compared to the file register set.

    The loading is done from R141 to R0.

    Any thoughts on why my down ramp is not working?

    Thanks, Jason.

    1800MHz_dual.txt
    Fullscreen
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    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
    R98,0x006202
    R97,0x0061FA
    R96,0x00603F
    R95,0x005FFD
    R94,0x005EF3
    R93,0x005DB6
    R92,0x005C24
    R91,0x005B04
    R90,0x005Ae2
    R89,0x005900
    R88,0x005800
    R87,0x005768
    R86,0x0056DB
    R85,0x005500
    R84,0x005400
    R83,0x005300
    R82,0x0052FF
    R81,0x0051FF
    R80,0x0050FF
    R79,0x004FFE
    R78,0x004EFF
    R77,0x004DFF
    R76,0x004CFF
    R75,0x004BFE
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

  • 0 in reply to Jason Tandy
    Prodigy 80 points

    Today I have repeated the flat top issue with the TICS Pro software on the EVAL board and currently am unable to clear it.

    Please see below images and the register set used.

    There must be something I am missing?


    EVAL flat top HexRegisterValues.txt
    Fullscreen
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    R141 0x008D00
    R140 0x008C00
    R139 0x008B00
    R138 0x008A00
    R137 0x008900
    R136 0x008800
    R135 0x008700
    R134 0x008600
    R133 0x008527
    R132 0x008410
    R131 0x008300
    R130 0x008200
    R129 0x008100
    R128 0x008000
    R127 0x007F00
    R126 0x007E27
    R125 0x007D10
    R124 0x007C00
    R123 0x007B00
    R122 0x007A00
    R121 0x007900
    R120 0x007800
    R119 0x007727
    R118 0x007610
    R117 0x007500
    R116 0x007400
    R115 0x007300
    R114 0x007200
    R113 0x007100
    R112 0x007027
    R111 0x006F10
    R110 0x006E00
    R109 0x006D00
    R108 0x006C00
    R107 0x006B00
    R106 0x006A00
    R105 0x006927
    R104 0x006810
    R103 0x00673F
    R102 0x0066FF
    R101 0x0065EC
    R100 0x006457
    R99 0x006340
    R98 0x006227
    R97 0x006110
    R96 0x006000
    R95 0x005F00
    R94 0x005E06
    R93 0x005D8E
    R92 0x005C24
    R91 0x005B27
    R90 0x005A10
    R89 0x005900
    R88 0x005800
    R87 0x00570D
    R86 0x00561B
    R85 0x005500
    R84 0x005400
    R83 0x005300
    R82 0x005218
    R81 0x005100
    R80 0x005000
    R79 0x004F00
    R78 0x004E7A
    R77 0x004D00
    R76 0x004C00
    R75 0x004B00
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

  • 0 in reply to Jason Tandy
    Prodigy 80 points
    Looks like the RAMP_LIMIT_LOW and RAMP_LIMIT_HIGH registers are getting bad values. More to come ...
  • 0 in reply to Jason Tandy
    TI__Mastermind 27851 points

    Jason,

    OK,  I'll wait for your response. 

    Regards,

    Dean

  • 0 in reply to Dean Banerjee
    Prodigy 80 points

    I have got the circuit performing as I expect.

    I used the CodeLoader program to generate a default file with settings that worked on the EVAL board and used this to set up my board.  Somewhere along the line the RAMP_LIMIT_LOW and _HIGH  registers were changed from there power on reset values.  This could stop the negative ramp I was after from working.  Changing the registers back to their power on value makes the ramp work.  These registers would appear to be changed when loading default configurations in CodeLoader and TICS Pro, leading to my confusion.  I believe that somehow CodeLoader changes these registers, so sometimes the negative ramp worked and sometimes it didn't.  I guess the TICS Pro Default Configuration file can have a similar effect.

    Regards, Jason.