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AS1545

Data Sheet - Te r m i n o l o g y

Zero Code Error

The Zero Code Error is the deviation of the midscale transition (all 0xFFFh to all 0x000h in 2’s complement output

Zero Code Error =

Zero Code Error Match

Fully Differential Mode (2’s complement output coding).

Positive Gain Error

The Positive Gain Error is the deviation last code transition (0x7FEh) to (0x7FFh) in 2’s complement output coding

Differential Mode.

Positive Gain Error =Zero Code Error –

Negative Gain Error

The Negative Gain Error is the deviation first code transition (0x800h) to (0xFFFh) in 2’s complement output coding

Differential Mode.

Negative Gain Error =

Positive / Negative Gain Error Match

The Positive / Negative Gain Error Match defines the maximum deviation of the Positive / Negative Gain Errors across

Signal-to-Noise Plus Distortion (SINAD)

The Signal to Noise Plus Distortion Ratio defines the ratio between the RMS value of the fundamental (input signal)

and the equivalent RMS value of all other spectral components below one-half the sampling frequency, including

harmonics but excluding DC. SINAD will be equal to SNR in an distortion free ADC.

Effective Number of Bits (ENOB)

The Effective Number of Bits indicates the actual resolution of the converter. The ENOB can be calculated from the

Signal to Noise Plus Distortion Ratio (SINAD).

ENOB =

Signal-to-Noise Ratio (SNR)

The Signal to Noise Ratio defines the ratio between the RMS value of the fundamental (input signal) to the RMS value

of the sum of all other spectral components below one-half of the sampling frequency, excluding harmonics and DC.

The theoretical SNR for an ideal N bit ADC is limited by the quantization error and is described by the formula:

SNR = 6.02*N +1.76 (dB)

Therefore, for a 12-bit ADC, the maximum SNR is 74dB.

VINP

VINN

–

VREF

-----------------------------------

4096

2048

+

×

AVG MeasuredCodes

()

–

VINP

VINN

–

VREF

-----------------------------------

4096

2048

+

×

AVG MeasuredCodes

()

–

⎩⎭

⎨⎬

⎧⎫

VINP

VINN

–

VREF

-----------------------------------

4096

2048

+

×

AVG MeasuredCodes

()

–

⎩⎭

⎨⎬

⎧⎫

ZeroCodeError

–

SINAD

1,76

–

6,02

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