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LMX2594: LMX2594 DOESN'T WORK

FRANCESCO FIUME
Prodigy 170 points
Part Number: LMX2594
Other Parts Discussed in Thread: USB2ANY, LMX2595

Good morning, I write this email to ask for explanations on the fact that, for the second time, the board LMX2594 had problems. I have used it several times being careful to feed it correctly and gradually. Unfortunately, once again, it happened that suddenly it no longer works. What to do? I state that the use of the board in question is bound to the only purpose of carrying out measurements in the laboratory through the use of instruments such as spectrum analyzers and oscilloscopes for the Master's degree thesis. We have time constraints and the need to use LMX2594. Now the problem is that neither board works. We await clarification from you.

  • 0
    TI__Guru** 106870 points
    Hi Francesco,

    Could you describe a bit more in detail what is not working? For example, no outputs; low output power; cannot change frequency; etc.
  • 0 in reply to Noel Fung
    Prodigy 170 points
    I state that the board worked but suddenly showed this great inconvenience.The main problem is related to the fact that all outputs do not produce anything when they are enabled (no signal on the spectrum analyzer). There are no short circuits on the inputs and outputs. Previously when I enabled the ramp function, I could display a ramp on the oscilloscope on the external VP_Tune pin. The only thing I can see on the VP_Tune pin is an increase in an offset when I increase the supply voltage from 0 to 3.3 volts No sign of life at the outputs becouse the powers are null. For example, when the board was working and I applied a simple signal of 9000 MHz, on the VP_Tune pin the offset went up and when I turned it off the offest went down.
  • 0 in reply to FRANCESCO FIUME
    TI__Mastermind 27981 points
    Francesco,
    Here's a few things to try.

    1. Establish Communication
    a. If you are using USB2ANY or Reference pro board and TICSPro, then in TICSPro go:
    USB Communications -> Interface, and then click the "identify" button. This establishes TICSPro is talking to USB2ANY/Reference Pro, but does NOT verify that the TICSPro/USB2ANY is being understood by the LMX2594
    b. Use low level serial commands to test communication that do no depend on the PLL locking such as POWERDOWN or RESET and look for the current to change in response to these.
    c. Make sure the device is powered down. There is a bit and a CE pin. I think on the EVM, the CE pin is tied high, but good to check.

    2. Establish Lock
    Apply valid reference, preferably 100 MHz as this is default. Under Default Configuration, Choose the appropriate Default Mode.

    Regards,
    Dean
  • 0 in reply to Dean Banerjee
    Prodigy 170 points
    Good morning, the problem persists even after carrying out the steps you have described to me. The CE is high when the circuit is powered the power supply on the Vtune_TP pin increases linearly with the power supply. I tried repeatedly to uninstall and install TICS Pro but no improvement. I tried to write the registers individually to give test commands but the system does not respond.
  • 0 in reply to FRANCESCO FIUME
    TI__Guru** 106870 points
    Hi Francesco,

    Something I don't understand - "the power supply on the Vtune_TP pin increases linearly with the power supply" and "The only thing I can see on the VP_Tune pin is an increase in an offset when I increase the supply voltage from 0 to 3.3 volts".
    In a normal operation, all necessary power supplies should exist before programming the device. Once it is locked, Vtune voltage should be a stable DC voltage. Were you able to simply make it lock to a certain frequency? What is the current consumption right now?
  • 0 in reply to Noel Fung
    Prodigy 170 points

    hi noel,

    the problem is that nothing works in the circuit anymore. It was working when suddenly it stopped working.

    When it still worked, under normal conditions ('device on' and 'output enabled') on the Vtune_TP pin there was an offset while when the "ramp" function was activated there was a ramp as shown in the figure. Now, the only thing I can notice is the presence of an offset on the Vtune_TP pin that grows in step with the power supply but nothing happens on the RFOUTa and RFOUTb outputs. In this last case the current absorption is about 200 mA. In normal conditions, in the case of an output signal at 9000 MHz, the absorption was equal to 400 mA, whereas in the presence of the ramp signal it was 430 mA. I tried to do all the tests that Dean suggested to me, but I can not solve the problem anyway.

  • 0 in reply to FRANCESCO FIUME
    TI__Mastermind 27981 points
    Francesco,
    Just to clarify, have you been able to to program the device with low level rudimentary commands like POWERDOWN and get it to respond? Have you been able to get it to lock in any state?

    Ramping (RAMP_EN=1) adds one more layer of potential things to go wrong.

    With 200 mA, this sounds like what you might get with the device powered up but both outputs powered down. But you should be able to change this to 0 mA by sending POWERDOWN=1. If this doesn't work, then we need to take a step back.

    Here's some things to try:
    1. For the MUXoutPin, set to lock detect. Does the PLL indiccate it is locked.

    2. If you can read bac, readback R110,R111,and R112 and get rb_VCO_SEL, rb_VCO_CAPCTRL, rb_VCO_DACISET, and rb_LD_VTUNE

    3. Make sure that OUT_MUTE=0 and OUT_FORCE=1

    Regards,
    Dean
  • 0 in reply to Dean Banerjee
    Prodigy 170 points
    Dean I put into practice everything you suggested but unfortunately does not change anything. I tried to write the registers in low-level but I have no positive feedback, I tried to enable and disable the POWERDOWN but the absorption in current always remains the same, I tried to perform the calibration as described but nothing yet one time .
  • 0 in reply to FRANCESCO FIUME
    TI__Mastermind 27981 points

    Francesco,

    OK, so what this means is that there's no point about talking about outputs or spectrum as there seems to be a more basic problem that the device is not responsive to programming at all.  Assuming that you are using TICSPro software, here's a few to do in this order.

    1.  Make sure it is not in "Demo Mode" and it says the USB2ANY board is detected. 

    2.  On TICSPro software, go menu commands to "USB Communications" -> "Interface", and then click the "Identify" button.  The green LED on the USB2ANY or ReferencePro board should blink.

    3.  On the 10 pin header cable between USB2ANY/ReferencePro board and the LMX2595 board, make sure this is securely plugged in.  It's a keyed connector, so it shouldn't be backwards, but sometimes this cable wears out.  You might want to ensure that an actual signal is coming out and getting to our board.  There are test points for this.

    4.  Ensure that you are not current limited on your power supply as the current consumption is likley more than 200 mA.

    5.  Ensure that there is a valid reference to the device.  I think that there is a 100 MHz XO on board, but ensure that the resistor (R10 I think ) that suppies power to this is placed and it is hooked up to the device.  If it's not hooked up, ensure a valid reference to our device.

    6.  Restore the default setup under "Default Configuration" -> Default Mode 2018-8-7 (or whatever the most current mode is).  Push Ctrl+L to load all registers.  If that doesn't work, try togging the RESET bit then pushing Ctrl+L to load all registers.  IF that still doesn't work, try cycling power, toggling the RESET bit, then pressing Ctrl+L

    7.  If still no success, tell us on which one of the 6 steps above there was not the expected result.

    Regards,

    Dean

  • 0 in reply to Dean Banerjee
    Prodigy 170 points

    Hi,

    I tried to run all 6 steps but nothing happens. Up to step number 5 everything is ok and I also tried to test the 10-pin connector. When I did the number 6 I did not notice any change. My doubt is: how is it possible that the system was damaged if everything worked correctly being subjected to an external power supply within the limits and a correct setting of the parameters?

  • 0 in reply to FRANCESCO FIUME
    TI__Guru** 106870 points
    Hi Francesco,

    I think it would be hard for us to give a conclusion here why it is not working now, unless we do the debug by ourselves.
    If you are in hurry getting it work again, I suggest you order a free sample right now and replace the old one.
  • 0 in reply to Noel Fung
    Prodigy 170 points

    Hi Noel,

    Can you explain to me what is the procedure to get the free sample? What are the times to be able to receive it? For sample you mean the entire circuit or the integrated component LMX2594? Thanks so much.

  • 0 in reply to FRANCESCO FIUME
    TI__Guru** 106870 points
    Hi Francesco,

    You can go to store.ti.com to get free sample (the IC).
  • 0 in reply to Noel Fung
    Prodigy 170 points
    Hi, I would like to ask if there is a chance to send you the damaged boards. Are you able to repair them?
  • 0 in reply to FRANCESCO FIUME
    TI__Mastermind 27981 points
    Francesco,

    I think that it unlikely that we sent you two defective boards and there are company policies that would interfere with shipping the board back to you. So we are not set up very well to do this.

    A few questions for you:
    1. Have you made any hardware changes to the board?
    2. Have you changed the TICSPro settings from default mode. If so, can you save a *.tcs file and we can look at that. Are you using TICSPro to program it?
    3. Can you elaborate on "doesn't work"? Does it mean ...
    a. Can not program the board. Even changing the POWERDOWN bit on the board does not cause the current to change
    b. Don't see any output at all
    c. See an output, but at the wrong frequency
    4. If using Reference pro or USB2ANY, can you communicate with this board? In TICSPro, you can try USB Communications -> Interface . In this, make sure you have the radio button for "USB2ANY" and also click the "Identify" button and it should blink the LED on the board.

    Regards,
    Dean