AD7927 VDRIVE-restriction

What’s the secret about the restriction in the abs. max. ratings of AD7927: “VDRIVE to AGND must be −0.3V to AVDD + 0.3V” and what happens if you don’t take care, e.g. if VDRIVE is powered up before AVDD? Could this damage the ADC?

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  • 0
    •  Analog Employees 
    on Jul 25, 2017 1:27 AM

    Hi matno2,

       The supplies for analog and digital circuitry in the IC are separate. There are circuitry inside the pat that needs to power up first before the other circuit. Like in the case of the AD7927. Need to power up the AVdd then the Vdrive.

       Each pin has a ESD protection diode. An overvoltage to the pin will forward bias the diode. This was explained on the AN932. This diodes are ESD protection diodes to protect the part from voltage spikes or an overvoltage on the pins. When this happen the part will be in unknown state. The performance of the part is not guaranteed at this state and high possibility that the part will be damaged when exposed for longer period of time.

    Regards,

    Jonathan

Reply
  • 0
    •  Analog Employees 
    on Jul 25, 2017 1:27 AM

    Hi matno2,

       The supplies for analog and digital circuitry in the IC are separate. There are circuitry inside the pat that needs to power up first before the other circuit. Like in the case of the AD7927. Need to power up the AVdd then the Vdrive.

       Each pin has a ESD protection diode. An overvoltage to the pin will forward bias the diode. This was explained on the AN932. This diodes are ESD protection diodes to protect the part from voltage spikes or an overvoltage on the pins. When this happen the part will be in unknown state. The performance of the part is not guaranteed at this state and high possibility that the part will be damaged when exposed for longer period of time.

    Regards,

    Jonathan

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