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AD7386 ADC Power-Up Sequence

Category: Hardware
Product Number: AD7386

Hello!

I'm planning to design with the AD7386 ADC.  The datasheet says that VCC, VLOGIC power inputs must be applied before the External reference is applied.  Furthermore, it says the External reference must be applied before analog and digital signals are applied. 

Would it be an issue if these are applied concurrently instead of sequenced ?  Is the sequence requirement there because of sneak-paths that could draw lots of current?

Appreciate any help, thanks!

Zackary

  • Hi Zackary,

         The AD7386 internal circuitry is powered up by Vcc and Vlogic. Powering the VCC and Vlogic first ensures that the internal circuitry has settled or has properly powered before driving voltage from external sources. Aside from the mentioned statement in the datasheet, this is also implicitly described in the abs/max rating of AD7386 datasheet. Abs/Max rating says that REFIO input to GND is in the range -0.3 to Vcc+0.3 or 4V. This means that it requires to power up Vcc first to know the range of the REFIO. Powering the external reference (REFIO) before the Vcc violates the Abs/Max rating, it may cause the device malfunction or damage.

          

    Regards,

    Jonathan 

  • Jonathan,

    Thank you for clarifying this.  I'll stick with sequencing the supplies as recommended.

    Appreciate it!

    Zack