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LMX2594: Chip not responding to SPI commands

Pierre Gellie
Prodigy 10 points
Part Number: LMX2594

Hi, I implemented a LMX2594 on a prototype board following closely the reference design and the EVM. Beside the 100MHz XO everything is identical. My XO is tested and works fine and is connected singled ended to the LMX2594.

My problem is that the chip does not responds to any SPI commands. Originally is used a STM microcontroller to program the chip, this was tested and proved on the LMX2594 EVM but no response from the chip on my board. I then tried to use the Reference pro board that came with the EVM to program my board but again not response.

Hardware wise, the chip when powered up takes 180mA on the 3.3V power supply so seems just about right for standby mode.

Any clues or test that I can perform?

Thanks

  • 0
    TI__Mastermind 28011 points
    Pierre,

    180 mA seems about right for power on reset current. For SPI testing, you can look at current consumption and try powering the device up and down.

    Normally, the things that one would think would be related to programming like:
    1. RESET bit is always 1
    2. CSB or CLK line is always high
    3. Logic levels
    4. Programming speed/timing wrong

    Now I am perplexed why your programming would work on our EVM, so this points to some hardware issue on your board.
    I'm not sure what hardware issues could cause this, but things that come to mind are:
    1. SPI lines crossed.
    2. SPI line missing: Are you sending all 4 lines: SDA, SCK, CSB, and GND
    3. Voltage divider or something reducing SPI voltages on your board.


    Regards,
    Dean