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ADC081C027

Isao Takigasaki
Intellectual 2950 points
Other Parts Discussed in Thread: ADC081C027

Hi

My customer is developing their system with ADC081C027.  They found a spike voltage at Vin pin.   

The spike appears at up-edge of CLK #9 of frame3 in "Figure 30. Typical Pointer Set Followed by Immediate Read of a 2-Byte ADC Register" in the datasheet.  The Vin should be about 0.8V constant.  The peak voltage of the spike is about 2.2V and the  width is about 1us. 

The Vin voltage is driven by buffer amp and no spike appears at output of the buffer when the output node is cut.  It's means the spike does not come from the buffer. 

What is the expected as the cause?
Is ICC of the ADC is increased at the up-edge of CLK#9 of frame3?

Best Regards, Taki    

  • 0
    TI__Genius 16890 points
    Hello,

    This is probably an artifact from the I2C communication. At the clock #9 you reference there is a change in the current of the communication. Up to that point the master has been communicating with the ADC081C027. On the 9th clock the master releases the SDA line and the ADC081C027 pulls down the line to ack the master. This change in current is probably causing the spike that you are seeing.

    Mike