AD7921 Analog Devices, AD7921 Datasheet - Page 13

• Manufacturer Part Number: AD7921
• Description: 2-Channel, 2.35 V to 5.25 V, 250 kSPS, 12-Bit A/D Converter
• Manufacturer: Analog Devices

Specifications of AD7921

• Resolution (bits): 12bit
• # Chan: 2
• Sample Rate: 250kSPS
• Interface: Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni Vdd
• Adc Architecture: SAR
• Pkg Type: SOP,SOT

TYPICAL PERFORMANCE CHARACTERISTICS
Figure 10 and Figure 11 show typical FFT plots for the AD7921
and AD7911, respectively, at a 250 kSPS sample rate and
100 kHz input frequency.
Figure 12 shows the SINAD ratio performance versus the input
frequency for various supply voltages while sampling at
250 kSPS with a SCLK frequency of 5 MHz for the AD7921.
Figure 13 shows the SNR ratio performance versus the input
frequency for various supply voltages while sampling at
250 kSPS with an SCLK frequency of 5 MHz for the AD7921.
–115
–115
–15
–35
–55
–75
–95
–15
–35
–55
–75
–95
5
5
Figure 10. AD7921 Dynamic Performance at 250 kSPS
Figure 11. AD7911 Dynamic Performance at 250 kSPS
0
0
8192 POINT FFT
V
F
F
SNR = 73.13dB
SINAD = 72.73dB
THD = –83.30dB
SFDR = –86.15dB
8192 POINT FFT
8192 POINT FFT
V
V
F
F
F
F
SNR = 61.75dB
SNR = 73.13dB
SINAD = 61.74dB
SINAD = 72.73dB
THD = –86.24dB
THD = –83.30dB
SFDR = –84.46dB
SFDR = –86.15dB
SAMP
IN
SAMP
SAMP
IN
IN
DD
DD
DD
= 100kHz
= 100kHz
= 100kHz
= 2.7V
= 2.7V
= 2.7V
= 250kSPS
= 250kSPS
20
= 250kSPS
20
40
40
FREQUENCY (kHz)
FREQUENCY (kHz)
60
60
80
80
100
100
120
120
Rev. A | Page 13 of 28
Figure 14 and Figure 15 show INL and DNL performance for
the AD7921.
Figure 16 shows a graph of the total harmonic distortion versus
the analog input frequency for different source impedances
when using a supply voltage of 3.6 V and a sampling rate of
250 kSPS. See the Analog Input section.
Figure 17 shows a graph of the total harmonic distortion versus
the analog input frequency for various supply voltages while
sampling at 250 kSPS with an SCLK frequency of 5 MHz.
Figure 18 shows the shutdown current versus the voltage supply
for different operating temperatures.
–70.5
–71.0
–71.5
–72.0
–72.5
–73.0
–73.5
–74.0
–72.0
–72.2
–72.4
–72.6
–72.8
–73.0
–73.2
–73.4
–73.6
Figure 12. AD7921 SINAD vs. Input Frequency at 250 kSPS
Figure 13. AD7921 SNR vs. Input Frequency at 250 kSPS
10
10
V
DD
V
= 5.25V
DD
V
DD
= 2.7V
V
V
DD
DD
= 4.75V
= 2.35V
V
= 2.7V
DD
= 4.75V
FREQUENCY (kHz)
FREQUENCY (kHz)
V
DD
100
100
= 3.6V
V
V
DD
V
DD
DD
= 2.35V
AD7911/AD7921
= 3.6V
= 5.25V
1k
1k