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Introduction
1.4 Product Family
Samsung ASIC
1-9
STDM110
(over a given temperature range) is sometimes substituted for a differential
nonlinearity specification since differential nonlinearity less than 1LSB is a suffi-
cient condition for monotonic behaviour.
2. Analog-to-Digital Converter
1. ILE (Integral Linearity Error: INL)
- Integral nonlinearity refers to the deviation
of each individual code from a line drawn from "zero" through "full scale". The
point used as "zero" occurs
1
/
2
LSB before the first code transition. "Full scale" is
defined as a level 1
1
/
2
LSB beyond the last code transition. The deviation is
measured from the center of each particular code to the true straight line.
2. DLE (Differential Linearity Error: DNL)
- An ideal ADC exhibits code
transitions that are exactly 1LSB apart. DNL is the deviation from this ideal value.
It is often specified in terms of the resolution for which no missing codes are
guaranteed.
3. Offset Error
- The first transition should occur at a level 1/2LSB above "zero".
Offset is defined as the deviation of the actual first code transition from that point.
4. Gain Error
- The first code transition should occur for an analog value 1/2LSB
above nominal negative full scale. The last transition should occur for an analog
value 1
1
/
2
LSB below the nominal positive full scale. Gain error is the deviation
of the actual difference between first and last code transitions and the ideal
difference between the first and last code transitions.
5. Pipeline Delay (Latency)
- The number of clock cycles between conversion
initiation and the associated output data being made available. New output data
is provided every clock cycle.
6. Effective Number of Bits (ENOB)
- This is a measure of a device's dynamic
performance and may be obtained from the SNDR or from a sine wave curve test
fit according to the following expression:
ENOB = SNDR - 1.76/6.02
ENOB = N-log2[RMS error (actual) / RMS error (ideal)]
7. Analog Bandwidth
- The analog input frequency at which the spectral power
of the fundamental frequency, as determined by FFT analysis is reduced by 3dB.
8. Aperture Delay
- The delay between the sampling clock and the instant the
analog input signal is sampled.
9. Aperture Jitter
- The sample to sample variation in aperture delay.
10. Bit Error Rate (BER)
- The number of spurious code errors produced for any
given input sine wave frequency at a given clock frequency. In this case it is the
number of codes occurring outside the histogram cusp for a 1/2 FS sine wave.
11. Signal to Noise Ratio
- This signal to noise ratio depends on the resolution
of the converter and automatically includes specifications of linearity, distortion,
sampling time uncertainty, glitches, noise, and settling time. Over half the
sampling frequency, this signal to noise ratio must be specified and should ideally
follow the theoretical formula;
S/N
max
= 6.02N + 1.76dB