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ADS8900B: How to correctly exit reset state with CS_N and CONVST connected together

Niels Leijen
Prodigy 10 points
Part Number: ADS8900B

Tool/software:

Good morning,

For a project, I need to minimize connections to and from the ADS8900. As there is no requirement for a specific conversion start time, I wanted to connect CS_N and CONVST together as shown in the minimum pin example in the datasheet:

However, later in the datasheet the following statement is made to exit the reset state:

This seems impossible with both connected to a single tra

Even further in the datasheet, the state machine is shown:

The state machine of the ADC seems to have no problem with connecting the signals together. As it only responds to edges of the CONVST signal so possibly the first sample is wrong, which is totally ok for the application.

Now the question remains:

is it possible to connect the pins together, even though the datasheet mentions that the CONVST needs to be low whilst keeping the CS_N high?

  • +1
    TI__Expert 7432 points

    Hi Niels,

    Thanks for your question, and patience as we were out of office for Thanksgiving holiday. I understand your confusion. From a previous E2E post, here is the answer:

    "Holding CONVST low when RST transitions from low-to-high is not a hard requirement, just a recommendation.

    In the case of a single control line for both /CS and CONVST, to exit the RESET state, the host controller can pull the /RST high, with SCLK held low and both /CS, CONVST pins held high."

    Hope that helps.

    Best regards,

    Samiha