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ADS8689: spec check

GARETH OU
Mastermind 9295 points
Part Number: ADS8689
Other Parts Discussed in Thread: ADS1118, ADS1260

Hi

The customer has a problem with the ADS8689. If the input terminal needs to be reset to 0 ohm, the problem can be corrected.

ADS8689 PIN 7,8 SHORT

The software does not receive a value that completely returns to 0.

There will be floating values ​​​​of 0.0033.0013. How should we correct it.

  • 0
    TI__Mastermind 37140 points

    Hi ,

    I'm trying to understand the customer's problem from description:

    "If the input terminal needs to be reset to 0 ohm, the problem can be corrected." I did not see any input terminal in your simple schematic, does this mean shorting "ANALOG_IN" to "PVSS" directly or via 0ohm resistor?

    I would suggest to use 0ohm resistor instead of 1Mohm for R7 and R13 which is critical and too high as front-end circuit.

    Also, 10kohm R15 and R14 will create an additional gain error for the customer, they can use 1kohm resistors.

    A solid ground plane is recommended for AGND and DGND, splitting ground could cause a violation to the voltage restriction between them, it depends on where the connection joint is and also layout design.

    Regards,

    Dale

  • 0 in reply to Dale Li
    Mastermind 9295 points

    Hi Dale

    Tanks for your reply

    customers need to test the voltage of 0-24V, refer to the configuration in PDF, Will the IC be burned if I don't use 1M?

    ADC sbaa244a.pdf

  • 0 in reply to GARETH OU
    TI__Mastermind 37140 points

    Hi ,

    ADS8689 can accept +/-20V input without a damage as long as the input current is limited, however the maximum unipolar input range is 0~12.288V, so a signal conditioning circuit (e.g. resistor divider as introduced in the app note or active circuit) should be used to scale +24V signal down to the normal input range of ADS8689, but a calibration is recommended to remove additional gain error which is caused by the large value series resistor. 

    To address the customer's concern, can you explain the tests they have done and the issue they are facing? It's not clear for me from your description.

    Regards,

    Dale

  • 0 in reply to Dale Li
    Mastermind 9295 points

    Hi Dale

    ADS8689 is mainly developed as EtherCat ADC Input. Customers will use it as an oscilloscope probe. If the input voltage range is allowed, they hope to reach 40+-, but the current application is 24+-. SPI is transmitted to our company through an isolation solution and Ethercat. EX CPU connection control. 3V is the baseboard input of our company's EDGU Goldfinger, and this model is a Goldfinger card application. Up to 4PCS ADC and DAC can be inserted to communicate with each other. ADC currently uses ADS1260, ADS118, and ADS8689. Currently, ADS1260 and ADS1118 are corrected without problems. Only ADS8689 has a problem that it cannot be initialized. The DAC uses the ADS8689.