SBASAL3B September   2024  – June 2025 ADC3668 , ADC3669

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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 (ADC3668 - 250 MSPS)
    8. 6.8  Electrical Characteristics - AC Specifications (ADC3669 - 500 MSPS)
    9. 6.9  Timing Requirements
    10. 6.10 Typical Characteristics, ADC3668
    11. 6.11 Typical Characteristics, ADC3669
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Analog Inputs
        1. 8.3.1.1 Nyquist Zone Selection
        2. 8.3.1.2 Analog Front End Design
      2. 8.3.2 Sampling Clock Input
      3. 8.3.3 Multi-Chip Synchronization
        1. 8.3.3.1 SYSREF Monitor
      4. 8.3.4 Time-Stamp
      5. 8.3.5 Overrange
      6. 8.3.6 External Voltage Reference
      7. 8.3.7 Digital Gain
      8. 8.3.8 Decimation Filter
        1. 8.3.8.1 Uncommon Decimation Ratios
        2. 8.3.8.2 Decimation Filter Response
        3. 8.3.8.3 Decimation Filter Configuration
        4. 8.3.8.4 Numerically Controlled Oscillator (NCO)
      9. 8.3.9 Digital Interface
        1. 8.3.9.1 Parallel LVDS (DDR)
        2. 8.3.9.2 Serial LVDS (SLVDS) with Decimation
          1. 8.3.9.2.1 SLVDS - Status Bit Insertion
        3. 8.3.9.3 Output Data Format
        4. 8.3.9.4 32-bit Output Resolution
        5. 8.3.9.5 Output Scrambler
        6. 8.3.9.6 Output MUX
        7. 8.3.9.7 Test Pattern
    4. 8.4 Device Functional Modes
      1. 8.4.1 Low Latency Mode
      2. 8.4.2 Digital Channel Averaging
      3. 8.4.3 Power Down Mode
    5. 8.5 Programming
      1. 8.5.1 GPIO Programming
      2. 8.5.2 Register Write
      3. 8.5.3 Register Read
      4. 8.5.4 Device Programming
      5. 8.5.5 Register Map
      6. 8.5.6 Detailed Register Description
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Wideband Spectrum Analyzer
      2. 9.2.2 Design Requirements
        1. 9.2.2.1 Input Signal Path
        2. 9.2.2.2 Clocking
      3. 9.2.3 Detailed Design Procedure
        1. 9.2.3.1 Sampling Clock
      4. 9.2.4 Application Performance Plots
      5. 9.2.5 Initialization Set Up
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Third-Party Products Disclaimer
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

8.3.1.2 Analog Front End Design

To optimize SNR and HD3 performance of the ADC, the recommendation is to add a RCR circuitry directly in front of the analog input. Figure 8-7 shows the recommended RCR circuitry for input frequencies less and greater than 500MHz (example shows AC coupling but same applies to DC coupling), assumimg a 50Ω source impedance. If the ADC is driven by an external amplifier, the RCR circuitry may not be needed.

ADC3668 ADC3669 External RCR for FIN < 500MHz (left) and FIN > 500MHz (right) Figure 8-7 External RCR for FIN < 500MHz (left) and FIN > 500MHz (right)