SBAS888B December   2020  – July 2022 ADC3664

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics - Power Consumption
    6. 6.6 Electrical Characteristics - DC Specifications
    7. 6.7 Electrical Characteristics - AC Specifications
    8. 6.8 Timing Requirements
    9. 6.9 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Analog Input
        1. 8.3.1.1 Analog Input Bandwidth
        2. 8.3.1.2 Analog Front End Design
          1. 8.3.1.2.1 Sampling Glitch Filter Design
          2. 8.3.1.2.2 Analog Input Termination and DC Bias
            1. 8.3.1.2.2.1 AC-Coupling
            2. 8.3.1.2.2.2 DC-Coupling
      2. 8.3.2 Clock Input
        1. 8.3.2.1 Single Ended vs Differential Clock Input
      3. 8.3.3 Voltage Reference
        1. 8.3.3.1 Internal voltage reference
        2. 8.3.3.2 External voltage reference (VREF)
        3. 8.3.3.3 External voltage reference with internal buffer (REFBUF)
      4. 8.3.4 Digital Down Converter
        1. 8.3.4.1 DDC MUX
        2. 8.3.4.2 Digital Filter Operation
        3. 8.3.4.3 FS/4 Mixing with Real Output
        4. 8.3.4.4 Numerically Controlled Oscillator (NCO) and Digital Mixer
        5. 8.3.4.5 Decimation Filter
        6. 8.3.4.6 SYNC
        7. 8.3.4.7 Output Formatting with Decimation
      5. 8.3.5 Digital Interface
        1. 8.3.5.1 Output Formatter
        2. 8.3.5.2 Output Bit Mapper
        3. 8.3.5.3 Output Interface/Mode Configuration
          1. 8.3.5.3.1 Configuration Example
        4. 8.3.5.4 Output Data Format
      6. 8.3.6 Test Pattern
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal operation
      2. 8.4.2 Power Down Options
    5. 8.5 Programming
      1. 8.5.1 Configuration using PINs only
      2. 8.5.2 Configuration using the SPI interface
        1. 8.5.2.1 Register Write
        2. 8.5.2.2 Register Read
    6. 8.6 Register Maps
      1. 8.6.1 Detailed Register Description
  9. 9 Application Information Disclaimer
    1. 9.1 Typical Application
      1. 9.1.1 Design Requirements
      2. 9.1.2 Detailed Design Procedure
        1. 9.1.2.1 Input Signal Path
        2. 9.1.2.2 Sampling Clock
        3. 9.1.2.3 Voltage Reference
      3. 9.1.3 Application Curves
    2. 9.2 Initialization Set Up
      1. 9.2.1 Register Initialization During Operation
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Receiving Notification of Documentation Updates
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

8.3.4 Digital Down Converter

The ADC3664 includes an optional on-chip digital down conversion (DDC) decimation filter that can be enabled via SPI register settings. It supports complex decimation by 2, 4, 8, 16 and 32 using a digital mixer and a 32-bit numerically controlled oscillator (NCO) as shown in Figure 8-15. Furthermore it supports a mode with real decimation where the complex mixer is bypassed (NCO should be set to 0 for lowest power consumption) and the digital filter acts as a low pass filter.

Internally the decimation filter calculations are performed with a 20-bit resolution in order to avoid any SNR degradation due to quantization noise limitation. The Output Formatter truncates to the selected resolution prior to outputting the data on the digital interface.

GUID-4DDF3984-66E0-412D-B101-A95944C315FE-low.gifFigure 8-15 Internal Digital Decimation Filter