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ADS7038: ADS7038IRTER Timing questions

Guangyan Liu
Intellectual 2130 points
Part Number: ADS7038

Dear Team 

Good day!

The ADS7038 datasheet shows the max for tCONV is 600ns.
What is the min for tCONV?
For example, if my tCYCLE is 1000ns and I need 600ns for acquiring the sample (tACQ) then could I make tCONV only 400ns?


Also, when I'm writing to registers like the GENERAL_CFG and SEQUENCE_CFG registers and I want to sample at 1MSPS
then do I still need to meet tCYCLE=1000ns during the register write or can it be 1800ns for example?
In other words can I use 1800ns to write to the GENERAL_CFG register then go back to tCYCLE=1000ns for my sampling and will everything be OK?

Thanks,

Leon.liu

  • +1
    TI__Guru 63905 points

    Hello,

    The maximum tCONV time should be used for all acquisition and timing calculations.  Some devices will convert faster than 600ns, but the maximum timing will ensure that all devices will be able to properly convert.

    In order to meet the 1MSPS (1us/sample) timing requirements the customer will need to configure for a 400ns tACQ and a 600ns tCONV.  

    You can read/write registers at various speeds during operation without issue provided all of the speeds meet the datasheet requirements.  So, there are no issues using a slower SCLK/SPI timing during configuration register read/writes compared with how you're clocking out data in the max 1MSPS operation.

  • 0
    Prodigy 10 points

    Collin,

    Thank you for the information.

    OK I'll use 600ns for tCONV and 615ns for tACQ so my tCYCLE is 1215ns.

    Is 1215ns OK, I don't see 1215ns in Table 4.

    I'm not using averaging.

    I'm using on-the-fly mode.

    My understanding is that I don't need to worry about Table 4 if I'm not using averaging and 

    I don't need to set the CLK_DIV and OSC_SEL registers if I'm not using averaging.

    Thanks,

    Kevin

  • 0 in reply to 6569651
    TI__Guru 63905 points

    Kevin,

    1215ns is fine for an overall cycle time.   You'll achieve a sample rate of roughly 823kSPS.  Table 4 is specifically for averaging mode operation.