AD7992 Analog Devices, AD7992 Datasheet - Page 15

• Manufacturer Part Number: AD7992
• Description: 2-Channel, 12-Bit ADC with I2C Compatible Interface in 10-Lead MSOP
• Manufacturer: Analog Devices

Specifications of AD7992

• Resolution (bits): 12bit
• # Chan: 2
• Sample Rate: 79kSPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni Vdd
• Adc Architecture: SAR
• Pkg Type: SOP

For ac applications, removing high frequency components from
the analog input signal is recommended by use of an RC band-
pass filter on the relevant analog input pin. In applications
where harmonic distortion and signal-to-noise ratio are critical,
the analog input should be driven from a low impedance
source. Large source impedances significantly affect the ac
performance of the ADC. This may necessitate the use of an
input buffer amplifier. The choice of the op amp is a function
of the particular application.
When no amplifier is used to drive the analog input, the source
impedance should be limited to low values. The maximum
source impedance depends on the amount of total harmonic
distortion (THD) that can be tolerated. THD increases as the
source impedance increases, and performance degrades.
Figure 22 shows the THD vs. the analog input signal frequency
when using supply voltages of 3 V ± 10% and 5 V ± 10%.
Figure 23 shows the THD vs. the analog input signal frequency
for different source impedances.
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Figure 22. THD vs. Analog Input Frequency for Various
Figure 23. THD vs. Analog Input Frequency for Various
Source Impedances for V
Supply Voltages, F
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
R
SOURCE
10
= 10 Ω
V
10
DD
S
DD
= 136 kSPS, Mode 1
R
= 5.5 V, 136 kSPS, Mode 1
SOURCE
V
= 5.5V
DD
= 3.3V
V
DD
V
= 50 Ω
DD
= 3.0V
R
= 4.5V
R
SOURCE
SOURCE
V
R
V
DD
SOURCE
V
V
V
REF
DD
REF
DD
= 2.7V
= 5.5V
= 2.5V
= 5.0V
= 2.5V
= 100 Ω
= 1k Ω
= 0 Ω
AD7992
100
100