LTC1411IG Просмотр технического описания (PDF) - Linear Technology
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LTC1411IG Datasheet PDF : 16 Pages
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LTC1411
APPLICATIO S I FOR ATIO
0
SINAD = 78.8dB
–20
SFDR = 95dB
fSAMPLE = 2.5MHz
fIN = 100kHz
–40
–60
–80
–100
–120
–140
0
250 500 750 1000 1250
INPUT FREQUENCY (kHz)
1411 G14
Figure 2a. LTC1411 Nonaveraged, 4096 Point FFT,
Input Frequency = 100kHz
0
SINAD = 75dB
–20
SFDR = 81dB
fSAMPLE = 2.5MHz
fIN = 1MHz
–40
–60
–80
–100
–120
–140
0
250 500 750 1000 1250
FREQUENCY (kHz)
1411 G15
Figure 2b. LTC1411 4096 Point FFT,
Input Frequency = 1MHz
86
80
74
68
62
56
50
44
38
32
26
20
14
10
14
13
12
11
10
100
1000
INPUT FREQUENCY (kHz)
10000
1411 TA02
Figure 3. Effective Bits and Signal/(Noise + Distortion)
vs Input Frequency
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
10
2ND THD
3RD
100
1000
INPUT FREQUENCY (kHz)
10000
1411 G03
Figure 4. Distortion vs Input Frequency
Effective Number of Bits
The effective number of bits (ENOBs) is a measurement of
the resolution of an ADC and is directly related to the
S/(N + D) by the equation:
ENOBS = [S/(N + D) – 1.76]/6.02
where S/(N + D) is expressed in dB. At the maximum
sampling rate of 2.5MHz the LTC1411 maintains good
ENOBs up to the Nyquist input frequency of 1.25MHz.
Refer to Figure␣ 3.
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS
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:
THD = 20log V22 + V32 + V42 + …VN2
V1
where V1 is the RMS amplitude of the fundamental fre-
quency and V2 through VN are the amplitudes of the
second through Nth harmonics. THD vs input frequency is
shown in Figure 4. The LTC1411 has good distortion
performance up to the Nyquist frequency and beyond.
1411f
9
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