AD7928 Analog Devices, AD7928 Datasheet - Page 13

• Manufacturer Part Number: AD7928
• Description: 8-Channel, 1 MSPS, 12-Bit ADC with Sequencer in 20-Lead TSSOP
• Manufacturer: Analog Devices

Specifications of AD7928

• Resolution (bits): 12bit
• # Chan: 8
• Sample Rate: 1MSPS
• Interface: Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni (Vref) x 2
• Adc Architecture: SAR
• Pkg Type: SOP

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 AV
frequency f
Pf is equal to the power at frequency f in ADC output; Pf
equal to the power at frequency f
supply. Here a 200 mV p-p sine wave is coupled onto the AV
supply.
PSRR(dB) = 10 log(Pf/Pfs)
–110
–50
–70
–10
–30
–90
75
70
65
60
55
Figure 5. AD7928 SINAD vs. Analog Input Frequency for
10
0
Figure 4. AD7928 Dynamic Performance at 1 MSPS
S
f
T
RANGE = 0V TO REF
SAMPLE
A
50
= 25°C
Various Supply Voltages at 1 MSPS
= 1MSPS
100
150
INPUT FREQUENCY (kHz)
FREQUENCY (kHz)
IN
200
100
250
S
coupled onto the ADC AV
300
AV
AV
AV
AV
DD
DD
DD
DD
350
4096 POINT FFT
AV
f
f
SINAD = 71.147dB
THD = –87.229dB
SFDR = –90.744dB
SAMPLE
IN
= V
= V
= V
= V
DD
= 50kHz
DD
DRIVE
DRIVE
DRIVE
DRIVE
400
= 5V
supply of
= 1MSPS
= 5.25V
= 4.75V
= 3.60V
= 2.70V
450
1000
500
S
is
Rev. D | Page 13 of 32
DD
DD
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.
–10
–20
–30
–40
–50
–60
–70
–80
–90
–50
–55
–60
–65
–70
–75
–80
–85
–90
0
10
0
Figure 7. AD7928 THD vs. Analog Input Frequency for
Figure 6. AD7928 PSRR vs. Supply Ripple Frequency
f
T
RANGE = 0V TO REF
AV
200mV p-p SINEWAVE ON AV
REF
T
SAMPLE
A
A
100
= 25°C
DD
= 25°C
IN
= 5V
= 2.5V, 1µF CAPACITOR
Various Supply Voltages at 1 MSPS
= 1MSPS
200
SUPPLY RIPPLE FREQUENCY (kHz)
300
INPUT FREQUENCY (kHz)
AD7908/AD7918/AD7928
IN
400
AV
100
DD
500
AV
DD
= V
DD
DRIVE
600
= V
AV
DRIVE
AV
= 2.70V
700
DD
DD
= V
= 5.25V
= V
800
DRIVE
DRIVE
= 3.60V
900
= 4.75V
1000
1000