Datasheet AD7609 (Analog Devices) - 31

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AD7609 Data Sheet 4500
When the oversampling mode is selected, this has the effect
OVERSAMPLING BY 16
of adding a digital filter function after the ADC. The different
4000 3833
oversampling rates and the CONVST x sampling frequency
3500 S 3279
produces different digital filter frequency profiles.
NCE 3000
Figure 54 to Figure 59 show the digital filter frequency profiles
2500 CCURE
for the different oversampling rates. The combination of the
O F 2000
analog antialiasing filter and the oversampling digital filter can
R O
be used to eliminate or reduce the complexity of the design of
BE 1500
the filter before the AD7609. The digital filtering combines
NUM 1000
steep roll-off and linear phase response.
657 500 406 385 0 AV 3 14 CC = 5V 0 V –10 DRIVE = 5V –3 –2 –1 0 1 2
048
TA = 25°C CODE 10V RANGE
09760-
–20 OS BY 2
Figure 51. Histogram of Codes—OS × 16 (Six Codes)
B) –30 d 6000 N ( OVERSAMPLING BY 32 –40 IO 5090 5000 –50 NUAT E S T –60 AT NCE 4000 –70 CCURE 3000 O –80 F 2716 R O –90 100 1k 10k 100k 1M 10M
051
BE 2000 FREQUENCY (Hz)
09760-
NUM
Figure 54. Digital Filter Response for OS × 2
1000 341 0 45 AVCC = 5V 0 V –2 –1 0 1
049
–10 DRIVE = 5V TA = 25°C CODE
09760-
–20 10V RANGE OS BY 4
Figure 52. Histogram of Codes—OS × 32 (Four Codes)
–30 B) d 7000 –40 N ( OVERSAMPLING BY 64 IO 5871 –50 6000 NUAT S E –60 T 5000 NCE AT –70 4000 –80 CCURE O F –90 3000 R O 2245 –100 BE 100 1k 10k 100k 1M 10M
052
2000 FREQUENCY (Hz) NUM
09760- Figure 55. Digital Filter Response for OS × 4
1000 1 75 0 –2 –1 0 1
050
CODE
09760- Figure 53. Histogram of Codes – OS × 64 (Four Codes) Rev. B | Page 30 of 36 Document Outline Features Applications Companion Products Functional Block Diagram Table of Contents Revision History General Description Specifications Timing Specifications Timing Diagrams Absolute Maximum Ratings Thermal Resistance ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Terminology Theory of Operation Converter Details Analog Input Analog Input Ranges Analog Input Impedance Analog Input Clamp Protection Analog Input Antialiasing Filter Track-and-Hold Amplifiers ADC Transfer Function Internal/External Reference External Reference Mode Internal Reference Mode Typical Connection Diagram Power-Down Modes Conversion Control Simultaneous Sampling on All Analog Input Channels Simultaneously Sampling Two Sets of Channels Digital Interface Parallel Interface (/PAR/SER SEL = 0) Serial Interface (/PAR/SER SEL = 1) Reading During Conversion Digital Filter Layout Guidelines Outline Dimensions Ordering Guide