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About the power supply sequence of AD7656A-1


I have a question about POWER SUPPLY SEQUENCING on page 6 of the AD7656A-1 data sheet.

① How much is the difference in input time between VDD and VSS acceptable?
② Does "VDD must power up before VSS." Mean that the voltage should be applied to the VDD terminals first?
   Or does it mean that VDD must first exceed a certain voltage?
③ Is there a regulation for rise time?
④ Is there a regulation when the power is turned off?
⑤ Are there any rules for turning the power on and off, including AVCC and DVCC?

I would appreciate it if you could reply.

Best Regards,

  • Hi, 

    1, Let me check if we have that data but I guess the important thing as the datasheet mentioned is that the VDD must power up before Vss. 

    2. I think power up means applying a positive voltage at VDD before applying a negative voltage at VSS. 

    3. Again, I'm not sure if this has been characterize. May I know how important this data in your application? Is it difficult from your end to perform the recommended sequence? 

    4. I guess in terms of power off, as a good practice you have to comply with the power up sequence so the last powered on will be the first to turn off. So that the power up sequence is still followed. But I will confirm this too. 

    5. I think the important to note here is to have AVCC and DVCC powered on first before applying any analog or digital inputs. There's no sequence in terms of AVCC and DVCC. But I think the DVCC must powered up first before having Vdrive. 

    We will try to seek more inputs from the responsible engineer handling this product.