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ADS54J60: SPI reads unexpected results

John Polak
Prodigy 141 points
Part Number: ADS54J60

I am having some trouble with SPI reads from the ADS54J60. I get unexpected results, for example general register 0x00 always reads 0x3c and general register 0x05 always reads 0xaa despite the fact that most of those bits should be 0.

From reading other forum posts I have ensured that the DevClk (650MHz) and Sysref (10.15625MHz) are present and SPI clk frequency (2MHz) is less than DevClk frequency/200. PDN pin is connected to GND.

What could be causing this problem?

  • 0
    TI__Guru* 91947 points

    John,

    Make sure to follow the power up sequence shown in section 10.1.Make sure to follow the sequence shown in Table 75 of the data sheet.

    In case this is an issue with your read, power down the device with a SPI command and see if the ADC current is reduced.

    Reset should be pulsed from low to high to low after the clocks are present.

    Regards,

    Jim

  • 0 in reply to jim s
    Prodigy 141 points

    Jim,

    Today I confirmed that we are following power on sequencing, and we are pulsing reset after the clocks are present.

    I wrote to Master Page register 26 to power down the ADS54J60, and I both observed reduced power consumption and I was able to read back that register correctly.

    When I read back the general registers I still get the same (incorrect) values.

    I will continue to investigate this behavior. If I am able to read the paged registers, I may be able to ignore the unexpected General Register reads.

    Best,

    John

  • 0 in reply to John Polak
    TI__Guru* 91947 points

    John,

    Some registers are write only and some require a reset for the values to get loaded (page 0x6800).

    Regards,

    Jim

  • 0 in reply to jim s
    Prodigy 141 points

    Thank you Jim,

    I am able to write to and read from all the relevant registers, so I will ignore the strange reads from the general registers.