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DAC Linearity error variance chip to chip

David Mittmann
Prodigy 130 points
Other Parts Discussed in Thread: DAC8581

I was looking at the DAC8581 Datatsheet  and I have a question about Figure 2. Linearity error vs. input code - pg. 5.

How is this graph created. Is this an average of several chips.  Can I assume most (if not all) 8581 with have a positive linearity error in the 32468 to 40960?

Thanks.

  • 0
    TI__Mastermind 43915 points

    David, 

    Figure 2 on page 5 is the behavior of one DAC8581 device and is considered a typical characteristic. The spec for the linearity error tested over a large number of devices during characterization is found on page 2 in the Electrical Characteristics. It is specified as typical +/-0.05% FSR. 

    The linearity behavior between codes 32468 and 40960 should not be assumed to be a positive error in all devices. Linearity error is a results of internal matching components (resistors, internal op amps, etc.). The DAC8581 is a String DAC architecture that is heavily dependent on the matching of the resistors in the string. Every resistor in the string will have some tolerance to it stating that its value may vary from its defined value by some percentage. So maybe in one device two resistors in the design are very closely matched but in another those same resistors have a little more variance creating a larger linearity around certain codes. For that reason we cannot guarantee a positive linearity error or negative linearity error around certain code ranges in all devices. We can only guarantee a range that the linearity error will stay within.

    Regards,

    Tony Calabria