【教學】Calculate ENOB of ADC in Cadence - Custom IC Design

各位小夥伴們,當各位設計好ADC或DAC的時候,我們一般都是去計算ENOB或INL,來

去判斷效能是否沒問題。

一般普遍大眾的作法，應該都是將ADC輸出轉出來，再用MATLAB去做運算。

這個方法雖然是沒問題，但是卻很浪費時間。

因此我們建議使用Cadenc內建的計算工具,來去幫我們算出ENOB和FFT。

Dear friends, when you design ADC or DAC, we usually calculate ENOB or INL 

to judge whether the performance is ok.

The general practice of the general public should be to transfer the ADC output, and then 

use MATLAB to do the calculation.This method is fine, but it's a waste of time.

Therefore, we recommend using Cadenc's built-in calculation tools to help us calculate 

ENOB and FFT.

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1.Open ADC Output Wave

下圖為16-bits SAR ADC輸出波形。

The figure below shows the 16-bits SAR ADC output waveform.

2.Open Tool

打開上面的Measure->Spectrum。

Open Measure->Spectrum.

3.Calculate ENOB/FFT

會出現右邊的欄框,按照以下步驟一步接著一步設定。

-設定 FFT Input Method =>Calculate Start Time

-設定結束時間(需要穩態點)

-設定取樣點數和取樣時間

-設定完上述,按遺下Start/End那欄的"s"

-設定Harmonic計算=>15

-設定完上述,按Plot

下圖為 16-bits 500KS/s ADC(取樣點數256點)

The right frame will appear, follow the steps below to set it step by step.

-Set FFT Input Method =>Calculate Start Time

- Set end time (requires steady state point)

- Set the number of sampling points and sampling time

- After setting the above, press the "s" in the Start/End column

- set Harmonic calculation => 15

- After setting the above, press Plot

The picture below shows a 16-bits 500KS/s ADC (256 sampling points)

4.Final Result

按下PLOT,會出現FFT圖形以及ENOB。

Press plot, the FFT graph and ENOB will appear.

ENOB : Effective number of bits

FFT : Fast Fourier Transform