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Introduction
1.4 Product Family
Samsung ASIC
1-7
STDM110
Figure 1-2.
Error of D/A Converter
3. LSB (Least-Significant Bit)
- In a system in which a numerical magnitude is
representedbyaseriesofbinarydigits,theLSBisthatbitthatcarriesthesmallest
value or weight.
It represents the smallest analog change that can be resolved
by an n-bit converter.
LSB (Analog Value) = FSR/2
n
FSR = Full-Scale Range, n = number of bits
4. MSB (Most-Significant Bit)
- The binary digit with the largest numerical
weighting. Normally, the MSB of a digital word has a weighting of 1/2 the full
range.
5. Compliance-Voltage Range
- For a current output DAC, the maximum range
of(output) terminal voltage for which the device will provide the specified current-
output characteristics.
6. Glitch
- A glitch is a switching transient appearing in the output during a code
transition. Its value is expressed as a product of voltage (V*ns) or current (mA*ns)
and time duration or charge transferred.
7. Harmonic Distortion (and Total Harmonic Distortion)
- The DAC is driven
by the digitized representation of sine wave. The ratio of the RMS sum of the
harmonics of the DAC output to the fundamental value is the THD. Usually only
the lower order harmonics are included, such as second through fifth.
2
------------+
log
=
V1: RMS amplitude of the fundamental
8. Signal-to-Noise Ratio (SNR)
- 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 follows the theoretical formula;
S/N
max
= 6.02N + 1.76dB
9. Slew Rate
- Slew rate of a device or circuit is a limitation in the rate of change
of output voltage, usually imposed by some basic circuit consideration such as
limited current to charge of capacitor. Amplifiers with slew rate of a few V/
μ
s are
common and moderate in cost. Slew rates greater than about 75 V/
μ
s are usually
seen only in more sophisticated (and expensive) devices The output slewing
speed of a voltage-output D/A converter is usually limited by the slew rate of the
amplifier used at its output (if one is used).
Offset Error
Ideal
Actual
Analog
Output
Digital Input
Analog
Output
Digital Input
Ideal
Actual
Gain Error
THD
20
V
3
2
V
4
2
V
1
V
5
2
+
+
)
1 2