INL and DNL validation of AD5668

Question

Hi 
 
 We are developing a system to rigorously test the AD5668, a crucial component in industrial control applications. Our primary objective is to thoroughly test and validate the device's performance against its datasheet specifications before proceeding with board assembly. 
 An evaluation board has been successfully developed and is currently functional. However, we are encountering challenges in accurately calculating the Integral Non-Linearity (INL) and Differential Non-Linearity (DNL) of the AD5668. 
 Could you please provide guidance on the established methods for calculating these critical parameters? 
 
 Thanks 
 Lokesha

dendalisay · Accepted Answer

Hi ReVxEnergyPrivateLimited , 
 Apologies for the late reply. To measure the INL and DNL, we use endpoint straight-line method for INL and standard step-size analysis for DNL. Could you share details about your test setup, like the precision of your voltmeter, settling time, and whether you&rsquo;re using a reduced code range? 
 For INL, you can use the endpoint method, which involves drawing a straight line between the DAC&rsquo;s output at the start and end of the tested code range. For example in a 16-bit DAC, it&rsquo;s common to exclude the zero-scale codes to minimize anomalies, typically focusing on a range like Codes 512 to 65,535. Measure the DAC output for each code and calculate its deviation from the ideal line. The maximum deviation across the range defines the INL. 
 For DNL, evaluate the step size between consecutive codes. Ideally, this step should equal 1 LSB. Any deviation from the expected step size (values commonly not just from a theoretical computed value but from a datasets from actual testing) represents the DNL error. If DNL is less than -1 LSB, it can indicate non-monotonic behavior. 
 Ensure you use a high-precision measurement devices, a stable and accurate voltage reference, and a controlled temperature environment. The DAC output should remain unloaded and allowed sufficient time to settle before taking measurements. 
 Br, 
 Den)

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INL and DNL validation of AD5668