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LMX2594: Default state of the LMX2594 when powered up

Vinayak Chabbi
Expert 1100 points
Part Number: LMX2594
Other Parts Discussed in Thread: USB2ANY, LM2594, MSP430F5528

Hi,

I want to know the default output status of the LMX2594, when it is powered up first.

I'm using 100MHz TCXO with 7833 MHz loop filter components.

Thanks in advance.

Regards,

Vinayak

  • 0
    TI__Guru* 81580 points
    Hi Vinayak,

    After Vcc power up, the internal POR will bring the device to the silicon default setting.
    In this state, Channel B is powered down; Channel A is div/2 output. Internal LDOs are turned ON but most of the functional blocks are powerdown, so you would not get any signal output from Channel A.
  • 0 in reply to Noel Fung
    Expert 1100 points

    Hello Fung,

    Thanks for the reply.

    One more query, I need to test the LMX2594 board, which is designed by me, is there any precaution we need to take for testing by default? If yes please give me the details.

    Thanks in advance.

    Regards,

    Vinayak 

  • 0 in reply to Vinayak Chabbi
    TI__Guru* 81580 points
    Hi Vinayak,

    If you have a USB2ANY or the Reference Pro board, program your board with one of them + TICS Pro. This will eliminate any software issue so that you can focus on the hardware.
  • 0 in reply to Noel Fung
    Expert 1100 points

    Hello Fung,

    Thanks for the reply and valuable info.

    Regards,

    Vinayak

  • 0 in reply to Vinayak Chabbi
    Expert 1100 points

    Hello Fung,
    As you said I'm trying to program my LM2594 using USB2ANY, I'm able to send the data , but how do I confirm that, am I writing or not? TICS Pro sending data even if I don't connect my LMX2594 board to USB2ANY. I'm keeping both outputs off. I can't turn it on right now because of my hardware constraints. Please help me through this.


    Thanks in advance.

  • 0 in reply to Vinayak Chabbi
    TI__Mastermind 27581 points

    Vinayak,

    To test that the LMX2594 is actually understanding commands from USB2ANY, try some of these  tricks:

    1.   Use the powerdown bit to power the device up and down.  You should see the current change.  If you can't measure current, look at the DC bias level at the OSCin pin.   It should be about 1.5V when powered up, 0V when powered down.

    2.  TICSPro allows you to read back registers.  To do so, set LD_MUXOUT_SEL to "ReadBack" and go to the "registers" tab and type in a register to readback.

    3.  If programming our EVM, the green light should come out when the PLL is locked.

    Regards,
    Dean

  • 0 in reply to Dean Banerjee
    Expert 1100 points

    Hello Dean,

    Thanks for the answer. It resolved my problem.

    Regards,

    Vinayak

  • 0 in reply to Dean Banerjee
    Expert 1100 points

    Hello Dean ,
    I'm trying to read the Register values from LMX2594, using my on board MSP430F5528 controller. Since I'm new to embedded coding I'm unable figure out, in which format does LMX2594 will send the data back? Is there any easiest way to communicate with LMX2594 other than using US2ANY with TICS PRO.

    Thanks,
    Vinayak

  • 0 in reply to Vinayak Chabbi
    TI__Guru* 81580 points
    Hi Vinayak,

    The readback data will come out from the MUXout pin after the 8th CLK.
    Before you do the readback, set R0 to make MUXout as register readback output.
    To read back, the MSB should be 1. You should program "1" + 7-bit address + 16-bit don't care. Use the CLK signal to sample the readback data.
  • 0 in reply to Noel Fung
    Expert 1100 points
    Hi Fung,
    Thanks for the reply, it didn't work.
    Right now I'm writing all the 113 registers in descending order (these all reg values taken from TICS pro, which locked at exact 7833MHZ) by making CSB low at starting of the write operation. Will this be fine ? (I also tried by making CSB LOW for every transaction starting and making it HIGH end of the transaction). My LMX2594 is enabling and giving me the output but LOCK is not happening.
    I'm using MSP430F5528, with UCB0 port for SPI communication.
    It will be very helpful if I get some example code for LMX2594.

    Thanks,
    Vinayak
  • 0 in reply to Vinayak Chabbi
    TI__Genius 9920 points

    Highlight some tips in yellow background for readback. I think you had done it as datasheet recommended.

  • 0 in reply to Vinayak Chabbi
    TI__Guru* 81580 points
    Hi Vinayak,

    Unfortunately, we do not have a sample code with the MSP controller.
    My suggestion is, run it at a slower SPI rate first, say 1MHz.
    CSB cannot be kept LOW throughout the 113 register write. CSB must be LOW at the beginning of a register write and must be HIGH after the register is written. So you should see 113 pulses in CSB.
    Also make sure you have the reference ready before you program the device.
    Suggested sequence:
    1. Vcc power up
    2. Provide a valid reference clock
    3. Program RESET=1
    4. Program RESET=0 (optional)
    5. Program all the registers in descending order
    6. Program R0 again (optional)