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ADS7066: SPI Hardware

David Nestler
Prodigy 40 points
Part Number: ADS7066
Other Parts Discussed in Thread: DAC70508,

Tool/software:

We are using your ADS7066IRTER and DAC70508ZYZFR in a design.  The ADS7066 and DAC70508 devices are on their own independent spi busses with an RFSoC serving as the SPI master for both devices.  The ADS7066 and DAC70508 devices are going to power on before the SPI Master powers on.  I want to know if there are any internal pull-ups on the SPI lines, Reset lines, or other digital IO that will connect to the RFSoC.  My concern is that, for example, if the MISO lines get pulled high by default by the ADS7066 or DAC70508 devices then this could inadvertently apply power through a GPIO port to the RFSoC and cause problems or damage.  I want to avoid placing buffers on these digital interfaces except for where I need to have it in order to protect the RFSoC. 

  • 0
    TI__Intellectual 1630 points

    Hello David, 

    As far as the ADS7066, this shouldn't be a concern, SPI pins are usually push-pull. The only pin the ADS7066 will drive would be the SDO, but only when CS is forced low. Weak pull-up resistors can be used on these lines to avoid accidentally driving the CS low at start up. The GPIO pins on the ADS7066 are accessed through the AIN pins, but they have to configured through the SPI bus, at power-up these pins are analog inputs and shouldn't drive anything either. 

    One of my counterparts in the DAC team can answer otherwise but it should be a similar case for the DAC70508. For this device the SDO pin can be configured as open drain (requiring a pull up) if it will be used as an alarm pin, but this would also have to be configured through the SPI communication. 

    Best regards,

    Yolanda