AD7908 View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'AD7908' PDF : 24 Pages View PDF
AD7908/AD7918/AD7928
TYPICAL PERFORMANCE CHARACTERISTICS
PERFORMANCE CURVES
Figure 4 shows a typical FFT plot for the AD7928 at 1 MSPS
sample rate and 50 kHz input frequency. Figure 5 shows the
signal-to-(noise + distortion) ratio performance vs. input
frequency for various supply voltages while sampling at 1 MSPS
with an SCLK of 20 MHz.
Figure 6 shows the power supply rejection ratio vs. supply ripple
frequency for the AD7928 when no decoupling is used. The
power supply rejection ratio is defined as the ratio of the power
in the ADC output at full-scale frequency f, to the power of a
200 mV p-p sine wave applied to the ADC AVDD supply of
frequency fS
PSRR(dB) = 10 log(Pf/Pfs)
Pf is equal to the power at frequency f in ADC output; PfS is
equal to the power at frequency fS coupled onto the ADC AVDD
supply. Here a 200 mV p-p sine wave is coupled onto the AVDD
supply.
–10
4096 POINT FFT
AVDD = 5V
fSAMPLE = 1MSPS
fIN = 50kHz
–30
SINAD = 71.147dB
THD = –87.229dB
SFDR = –90.744dB
–50
–70
–90
–110
0
50 100 150 200 250 300 350 400 450 500
FREQUENCY (kHz)
Figure 4. AD7928 Dynamic Performance at 1 MSPS
75
AVDD = VDRIVE = 5.25V
AVDD = VDRIVE = 4.75V
70
Figure 7 shows a graph of total harmonic distortion vs. analog
input frequency for various supply voltages, and Figure 8 shows a
graph of total harmonic distortion vs. analog input frequency
for various source impedances. See the Analog Input section.
Figure 9 and Figure 10 show typical INL and DNL plots for the
AD7928.
0
AVDD = 5V
–10 200mV p-p SINEWAVE ON AVDD
REFIN = 2.5V, 1µF CAPACITOR
–20 TA = 25°C
–30
–40
–50
–60
–70
–80
–90
0
100 200 300 400 500 600 700 800 900 1000
SUPPLY RIPPLE FREQUENCY (kHz)
Figure 6. AD7928 PSRR vs. Supply Ripple Frequency
–50
fSAMPLE = 1MSPS
–55 TA = 25°C
RANGE = 0V TO REFIN AVDD = VDRIVE = 2.70V
–60
–65
AVDD = VDRIVE = 3.60V
–70
–75
–80
AVDD = VDRIVE = 4.75V
–85
–90
10
AVDD = VDRIVE = 5.25V
100
INPUT FREQUENCY (kHz)
1000
Figure 7. AD7928 THD vs. Analog Input Frequency for
Various Supply Voltages at 1 MSPS
AVDD = VDRIVE = 3.60V
65
60
fSAMPLE = 1MSPS
TA = 25°C
RANGE = 0V TO REFIN
AVDD = VDRIVE = 2.70V
55
10
100
INPUT FREQUENCY (kHz)
1000
Figure 5. AD7928 SINAD vs. Analog Input Frequency for
Various Supply Voltages at 1 MSPS
Rev. D | Page 13 of 32
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