ADC12D040

SNAS171E – JUNE 2002 – REVISED MARCH 2013

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AC Electrical Characteristics (continued)

Unless otherwise specified, the following specifications apply for AGND = DGND = DR GND = 0V, VA = VD = +5V, VDR =

+3.0V, PD = 0V, INT/EXT = VD, VREF = +2.0V,OEA, OEB = 0V, fCLK = 40 MHz, tr = tf = 3 ns, CL = 20 pF/pin. Boldface limits

apply for TJ = TMIN to TMAX: all other limits TJ = 25°C

(1)(2)(3)(4)

Typical

Limits

Units

Symbol

Parameter

Conditions

(5)

(5)

(Limits)

tDIS

Data outputs into TRI-STATE Mode

4

ns

tEN

Data Outputs Active after TRI-STATE

4

ns

tPD

Power Down Mode Exit Cycle

500

ns

Figure 2.

Specification Definitions

APERTURE DELAY is the time after the rising edge of the clock to when the input signal is acquired or held for

conversion.

APERTURE JITTER (APERTURE UNCERTAINTY) is the variation in aperture delay from sample to sample.

Aperture jitter manifests itself as noise in the output.

CLOCK DUTY CYCLE is the ratio of the time during one cycle that a repetitive digital waveform is high to the

total time of one period. The specification here refers to the ADC clock input signal.

COMMON MODE VOLTAGE (VCM) is the d.c. potential present at both signal inputs to the ADC.

CONVERSION LATENCY See PIPELINE DELAY.

CROSSTALK is coupling of energy from one channel into the other channel.

DIFFERENTIAL NON-LINEARITY (DNL) is the measure of the maximum deviation from the ideal step size of 1

LSB.

EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE BITS) is another method of specifying Signal-to-Noise

and Distortion or SINAD. ENOB is defined as (SINAD - 1.76) / 6.02 and says that the converter is equivalent to a

perfect ADC of this (ENOB) number of bits.

FULL POWER BANDWIDTH is a measure of the frequency at which the reconstructed output fundamental

drops 3 dB below its low frequency value for a full scale input.

GAIN ERROR is the deviation from the ideal slope of the transfer function. It can be calculated as:

Gain Error = Positive Full Scale Error

− Negative Full-Scale Error

(1)

Gain Error can also be separated into Positive Gain Error and Negative Gain Error, which are.

PGE = Positive Full-Scale Error

− Offset Error

(2)

NGE = Offset Error

− Negative Full-Scale Error

(3)

GAIN ERROR MATCHING is the difference in gain errors between the two converters divided by the average

gain of the converters.

10

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