AD7927–Typical Performance Characteristics
PERFORMANCE CURVES
TPC 1 shows a typical FFT plot for the AD7927 at 200 kSPS
sample rate and 50 kHz input frequency. TPC 2 shows the
signal-to-(noise + distortion) ratio performance versus input
frequency for various supply voltages while sampling at 200 kSPS
with an SCLK of 20 MHz.
TPC 3 shows the power supply rejection ratio versus supply
ripple frequency for the AD7927 with no decoupling. 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.
4096 POINT FFT
AVDD = 4.75V
–10
fSAMPLE = 200kSPS
fIN = 50kHz
SINAD = 70.714dB
THD = ؊82.853dB
–30
SFDR = ؊84.815dB
–50
TPC 4 shows a graph of total harmonic distortion versus analog
input frequency for various supply voltages, while TPC 5 shows
a graph of total harmonic distortion versus analog input frequency
for various source impedances. See the Analog Input section.
TPC 6 and TPC 7 show typical INL and DNL plots for the
AD7927.
0
AVDD = 5V
–10 200mV p-p SINE WAVE ON AVDD
REFIN = 2.5V, 1F CAPACITOR
–20 TA = 25؇C
–30
–40
–50
–60
–70
–80
–90
0
20 40 60 80 100 120 140 160 180 200
SUPPLY RIPPLE FREQUENCY – kHz
TPC 3. PSRR vs. Supply Ripple Frequency
–50
–70
fSAMPLE = 200kSPS
–55
TA = 25؇C
RANGE = 0 TO REFIN
–90
–60
–110
–65
0 10 20 30 40 50 60 70 80 90 100
FREQUENCY – kHz
–70
TPC 1. Dynamic Performance at 200 kSPS
AVDD = V DRIVE = 2.7V
–75
AVDD = V DRIVE = 3.6V
75
–80
AVDD = V DRIVE = 5.25V
AVDD = V DRIVE = 4.75V
70
AVDD = V DRIVE = 3.6V
AVDD = V DRIVE = 2.7V
65
fSAMPLE = 200kSPS
TA = 25؇C
RANGE = 0 TO REFIN
60
0
100
INPUT FREQUENCY – kHz
TPC 2. SINAD vs. Analog Input Frequency for Various
Supply Voltages at 200 kSPS
–85
–90
10
AVDD = V DRIVE = 4.75V
AVDD = V DRIVE = 5.25V
100
INPUT FREQUENCY – kHz
TPC 4. THD vs. Analog Input Frequency for Various
Supply Voltages at 200 kSPS
–55
fSAMPLE = 200kSPS
–60 TA = 25؇C
AVDD = 5.25V
RANGE = 0 TO REFIN
–65
–70
RIN = 1000⍀
–75
–80
RIN = 100⍀
–85
RIN = 10⍀
–90
–95
10
RIN = 50⍀
100
INPUT FREQUENCY – kHz
TPC 5. THD vs. Analog Input Frequency for Various
Source Impedances
–8–
REV. 0