ADS6445 datasheet(68/75 Pages) STMICROELECTRONICS

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DEFINITION OF SPECIFICATIONS

SNR + 10Log10

(3)

SINAD + 10Log10

PN ) PD

(4)

ENOB +

SINAD * 1.76

6.02

(5)

ADS6445, ADS6444

ADS6443, ADS6442

SLAS531 – MAY 2007

Analog Bandwidth – The analog input frequency at which the power of the fundamental is reduced by 3 dB

with respect to the low frequency value.

Aperture Delay – The delay in time between the rising edge of the input sampling clock and the actual time at

which the sampling occurs. This delay will be different across channels. The maximum variation is specified as

aperture delay variation (channel-channel).

Aperture Uncertainty (Jitter) – The sample-to-sample variation in aperture delay.

Clock Pulse Width/Duty Cycle – The duty cycle of a clock signal is the ratio of the time the clock signal

remains at a logic high (clock pulse width) to the period of the clock signal. Duty cycle is typically expressed as a

percentage. A perfect differential sine-wave clock results in a 50% duty cycle.

Maximum Conversion Rate – The maximum sampling rate at which certified operation is given. All parametric

testing is performed at this sampling rate unless otherwise noted.

Minimum Conversion Rate –The minimum sampling rate at which the ADC functions.

Differential Nonlinearity (DNL) – An ideal ADC exhibits code transitions at analog input values spaced exactly

1 LSB apart. The DNL is the deviation of any single step from this ideal value, measured in units of LSBs.

Integral Nonlinearity (INL) – The INL is the deviation of the ADC's transfer function from a best fit line

determined by a least squares curve fit of that transfer function, measured in units of LSBs.

Gain Error – The gain error is the deviation of the ADC's actual input full-scale range from its ideal value. The

gain error is given as a percentage of the ideal input full-scale range. The gain error does not include the error

caused by the internal reference deviation from ideal value. This is specifed separately as internal reference

error. The maximum variation of the gain error across devices and across channels within a device is specified

separately.

Offset Error – The offset error is the difference, given in number of LSBs, between the ADC's actual average

idle channel output code and the ideal average idle channel output code. This quantity is often mapped into mV.

Temperature Drift – The temperature drift coefficient (with respect to gain error and offset error) specifies the

change per degree Celsius of the parameter from TMIN to TMAX. It is calculated by dividing the maximum

deviation of the parameter across the TMIN to TMAX range by the difference TMAX–TMIN.

Signal-to-Noise Ratio – SNR is the ratio of the power of the fundamental (PS) to the noise floor power (PN),

excluding the power at DC and the first nine harmonics.

SNR is either given in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the

reference, or dBFS (dB to full scale) when the power of the fundamental is extrapolated to the converter’s

full-scale range.

Signal-to-Noise and Distortion (SINAD) – SINAD is the ratio of the power of the fundamental (PS) to the power

of all the other spectral components including noise (PN) and distortion (PD), but excluding dc.

SINAD is either given in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the

reference, or dBFS (dB to full scale) when the power of the fundamental is extrapolated to the converter's

full-scale range.

Effective Number of Bits (ENOB) – The ENOB is a measure of a converter’s performance as compared to the

theoretical limit based on quantization noise.

Total Harmonic Distortion (THD) – THD is the ratio of the power of the fundamental (PS) to the power of the

first nine harmonics (PD).

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