AS1419A AUSTIN [Austin Semiconductor], AS1419A Datasheet - Page 9

• Manufacturer Part Number: AS1419A
• Description: 14 Bit, 800ksps Sampling A/D Converter with Shutdown
• Manufacturer: AUSTIN [Austin Semiconductor]

Signal-to-Noise Ratio
ratio between the RMS amplitude of the fundamental input
frequency to the RMS amplitude of all other frequency
components at the A/D output. The output is band limited to
frequencies from above DC and below half the sampling
frequency. Figure 2 shows a typical spectral content with a
800kHz sampling rate and a 100kHz input. The dynamic
performance is excellent for input frequencies up to and
beyond the Nyquist limit of 400kHz.
Effective Number of Bits
the resolution of an ADC and is directly related to the S/(N + D)
by the equation:
where N is the effective number of bits of resolution and
S/(N + D) is expressed in dB. At the maximum sampling rate of
800kHz, the AS1419 maintains near ideal ENOBs up to the
Nyquist input frequency of 400kHz (refer to Figure 3).
AS1419 & AS1419A
Rev. 1.5 08/09
(Noise+Distortion) vs. Input Frequency
FIGURE 3:
The signal-to-noise plus distortion ratio [S/(N + D)] is the
The effective number of bits (ENOBs) is a measurement of
N = [S/(N + D) – 1.76]/6.02
Effective Bits and Signal/
Austin Semiconductor, Inc.
9
Total Harmonic Distortion
sum of all harmonics of the input signal to the fundamental
itself. The out-of-band harmonics alias into the frequency band
between DC and half the sampling frequency. THD is expressed
as:
where V1 is the RMS amplitude of the fundamental frequency
and V2 through Vn are the amplitudes of the second through
nth harmonics. THD vs Input Frequency is shown in Figure 4.
The AS1419 has good distortion performance up to the Nyquist
frequency and beyond.
FIGURE 4:
FIGURE 5:
Plot
Total harmonic distortion (THD) is the ratio of the RMS
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
Distortion vs. Input Frequency
Intermodulation Distortion
AS1419A
AS1419
ADC
ADC
ADC
ADC
ADC