Datasheet LTC1419 (Analog Devices) - 8
| Fabricante | Analog Devices |
| Descripción | 14-Bit, 800ksps Sampling A/D Converter with Shutdown |
| Páginas / Página | 20 / 8 — APPLICATIONS INFORMATION. Effective Number of Bits. Figure 2a. LTC1419 … |
| Formato / tamaño de archivo | PDF / 270 Kb |
| Idioma del documento | Inglés |
APPLICATIONS INFORMATION. Effective Number of Bits. Figure 2a. LTC1419 Nonaveraged, 4096 Point FFT,. Input Frequency = 100kHz
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LTC1419
U U W U APPLICATIONS INFORMATION
frequencies outside the fundamental. Figure 2 shows a
Effective Number of Bits
typical LTC1419 FFT plot. The effective number of bits (ENOBs) is a measurement of the resolution of an ADC and is directly related to the 0 fSAMPLE = 800kHz S/(N + D) by the equation: – 20 fIN = 99.804687kHz SFDR = 98dB N = [S/(N + D) – 1.76]/6.02 THD = –93.3dB – 40 where N is the effective number of bits of resolution and – 60 S/(N + D) is expressed in dB. At the maximum sampling – 80 rate of 800kHz, the LTC1419 maintains near ideal ENOBs AMPLITUDE (dB) up to the Nyquist input frequency of 400kHz (refer to –100 Figure 3). –120 –140 14 86 0 50 100 150 200 250 300 350 400 13 80 SIGNAL/(NOISE + DISTORTION) (dB) FREQUENCY (kHz) 12 74 1419 F02a 11 68
Figure 2a. LTC1419 Nonaveraged, 4096 Point FFT,
10 62
Input Frequency = 100kHz
9 8 7 0 EFFECTIVE BITS 6 fSAMPLE = 800kHz 5 – 20 fIN = 375kHz SFDR = 88.3dB 4 SINAD = 80.1 – 40 3 fSAMPLE = 800kHz 2 – 60 1k 10k 100k 1M 2M INPUT FREQUENCY (Hz) – 80 1419 TA02 AMPLITUDE (dB) –100
Figure 3. Effective Bits and Signal/(Noise + Distortion) vs Input Frequency
–120 –140 0 50 100 150 200 250 300 350 400 FREQUENCY (kHz)
Total Harmonic Distortion
1419 F02b Total harmonic distortion (THD) is the ratio of the RMS
Figure 2b. LTC1419 Nonaveraged, 4096 Point FFT,
sum of all harmonics of the input signal to the fundamental
Input Frequency = 375kHz
itself. The out-of-band harmonics alias into the frequency band between DC and half the sampling frequency. THD is
Signal-to-Noise Ratio
expressed as: The signal-to-noise plus distortion ratio [S/(N + D)] is the V22 V32 V42 Vn2 ratio between the RMS amplitude of the fundamental input THD = + + +… Log 20 frequency to the RMS amplitude of all other frequency V1 components at the A/D output. The output is band limited where V1 is the RMS amplitude of the fundamental fre- to frequencies from above DC and below half the sampling quency and V2 through Vn are the amplitudes of the frequency. Figure 2 shows a typical spectral content with second through nth harmonics. THD vs Input Frequency is a 800kHz sampling rate and a 100kHz input. The dynamic shown in Figure 4. The LTC1419 has good distortion performance is excellent for input frequencies up to and performance up to the Nyquist frequency and beyond. beyond the Nyquist limit of 400kHz. 1419fb 8
U U W U APPLICATIONS INFORMATION
frequencies outside the fundamental. Figure 2 shows a
Effective Number of Bits
typical LTC1419 FFT plot. The effective number of bits (ENOBs) is a measurement of the resolution of an ADC and is directly related to the 0 fSAMPLE = 800kHz S/(N + D) by the equation: – 20 fIN = 99.804687kHz SFDR = 98dB N = [S/(N + D) – 1.76]/6.02 THD = –93.3dB – 40 where N is the effective number of bits of resolution and – 60 S/(N + D) is expressed in dB. At the maximum sampling – 80 rate of 800kHz, the LTC1419 maintains near ideal ENOBs AMPLITUDE (dB) up to the Nyquist input frequency of 400kHz (refer to –100 Figure 3). –120 –140 14 86 0 50 100 150 200 250 300 350 400 13 80 SIGNAL/(NOISE + DISTORTION) (dB) FREQUENCY (kHz) 12 74 1419 F02a 11 68
Figure 2a. LTC1419 Nonaveraged, 4096 Point FFT,
10 62
Input Frequency = 100kHz
9 8 7 0 EFFECTIVE BITS 6 fSAMPLE = 800kHz 5 – 20 fIN = 375kHz SFDR = 88.3dB 4 SINAD = 80.1 – 40 3 fSAMPLE = 800kHz 2 – 60 1k 10k 100k 1M 2M INPUT FREQUENCY (Hz) – 80 1419 TA02 AMPLITUDE (dB) –100
Figure 3. Effective Bits and Signal/(Noise + Distortion) vs Input Frequency
–120 –140 0 50 100 150 200 250 300 350 400 FREQUENCY (kHz)
Total Harmonic Distortion
1419 F02b Total harmonic distortion (THD) is the ratio of the RMS
Figure 2b. LTC1419 Nonaveraged, 4096 Point FFT,
sum of all harmonics of the input signal to the fundamental
Input Frequency = 375kHz
itself. The out-of-band harmonics alias into the frequency band between DC and half the sampling frequency. THD is
Signal-to-Noise Ratio
expressed as: The signal-to-noise plus distortion ratio [S/(N + D)] is the V22 V32 V42 Vn2 ratio between the RMS amplitude of the fundamental input THD = + + +… Log 20 frequency to the RMS amplitude of all other frequency V1 components at the A/D output. The output is band limited where V1 is the RMS amplitude of the fundamental fre- to frequencies from above DC and below half the sampling quency and V2 through Vn are the amplitudes of the frequency. Figure 2 shows a typical spectral content with second through nth harmonics. THD vs Input Frequency is a 800kHz sampling rate and a 100kHz input. The dynamic shown in Figure 4. The LTC1419 has good distortion performance is excellent for input frequencies up to and performance up to the Nyquist frequency and beyond. beyond the Nyquist limit of 400kHz. 1419fb 8