ADN2807 查看數據表（PDF） - Analog Devices

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ADN2807

155/622 Mb/s Clock and Data Recovery IC with Integrated Limiting Amplifier

Analog Devices 

Data Sheet

DEFINITION OF TERMS

MAXIMUM, MINIMUM, AND TYPICAL

SPECIFICATIONS

Specifications for every parameter are derived from statistical

analyses of data taken on multiple devices from multiple wafer

lots. Typical specifications are the mean of the distribution of

the data for that parameter. If a parameter has a maximum (or a

minimum) value, that value is calculated by adding to (or

subtracting from) the mean six times the standard deviation of

the distribution. This procedure is intended to tolerate pro-

duction variations. If the mean shifts by 1.5 standard deviations,

the remaining 4.5 standard deviations still provide a failure rate

of only 3.4 parts per million. For all tested parameters, the test

limits are guardbanded to account for tester variation, and

therefore guarantee that no device is shipped outside of data

sheet specifications.

INPUT SENSITIVITY AND INPUT OVERDRIVE

Sensitivity and overdrive specifications for the quantizer involve

offset voltage, gain, and noise. The relationship between the

logic output of the quantizer and the analog voltage input is

shown in Figure 8. For sufficiently large positive input voltage,

the output is always Logic 1; similarly for negative inputs, the

output is always Logic 0. However, the transitions between

output Logic Levels 1 and 0 are not at precisely defined input

voltage levels, but occur over a range of input voltages. Within

this zone of confusion, the output may be either 1 or 0, or it

may even fail to attain a valid logic state. The width of this zone

is determined by the input voltage noise of the quantizer. The

center of the zone of confusion is the quantizer input offset

voltage. Input overdrive is the magnitude of signal required to

guarantee a correct logic level with a 1 × 10–10 confidence level.

OUTPUT

1

NOISE

0

OFFSET

INPUT (V p-p)

OVERDRIVE

SENSITIVITY

(2× OVERDRIVE)

Figure 8. Input Sensitivity and Input Overdrive

ADN2807

SINGLE-ENDED VS. DIFFERENTIAL

AC coupling typically drives the inputs to the quantizer. The

inputs are internally dc-biased to a common-mode potential of

~0.6 V. Driving the ADN2807 single-ended and observing the

quantizer input with an oscilloscope probe at the point

indicated in Figure 9 shows a binary signal with average value

equal to the common-mode potential and instantaneous values

both above and below the average value. It is convenient to

measure the peak-to-peak amplitude of this signal and call the

minimum required value the quantizer sensitivity. Referring to

Figure 8, since both positive and negative offsets need to be

accommodated, the sensitivity is twice the overdrive.

10mV p-p

VREF

SCOPE

PROBE

ADN2807

PIN

+

QUANTIZER

VREF

50Ω 50Ω

Figure 9. Single-Ended Sensitivity Measurement

5mV p-p

VREF

SCOPE

PROBE

ADN2807

PIN

+

QUANTIZER

NIN

VREF

50Ω 50Ω

Figure 10. Differential Sensitivity Measurement

Driving the ADN2807 differentially (Figure 10), sensitivity

seems to improve by observing the quantizer input with an

oscilloscope probe. This is an illusion caused by the use of a

single-ended probe. A 5 mV p-p signal appears to drive the

ADN2807 quantizer. However, the single-ended probe

measures only half the signal. The true quantizer input signal is

twice this value since the other quantizer input is

complementary to the signal being observed.

Rev. B | Page 9 of 21

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