SBASAD1A December   2023  – May 2024 ADC3910D025 , ADC3910D065 , ADC3910D125 , ADC3910S025 , ADC3910S065 , ADC3910S125

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Thermal Information
    5. 5.5  Electrical Characteristics - Power Consumption
    6. 5.6  Electrical Characteristics - DC Specifications
    7. 5.7  Electrical Characteristics - AC Specifications (25 MSPS)
    8. 5.8  Electrical Characteristics - AC Specifications (65 MSPS)
    9. 5.9  Electrical Characteristics - AC Specifications (125 MSPS)
    10. 5.10 Timing Requirements
    11. 5.11 Output Interface Timing Diagram
    12. 5.12 Typical Characteristics - 25MSPS
    13. 5.13 Typical Characteristics - 65MSPS
    14. 5.14 Typical Characteristics - 125MSPS
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 ADC Features
        1. 6.3.1.1 Low Latency Mode
        2. 6.3.1.2 Full Digital Feature Mode
        3. 6.3.1.3 Interleaving Mode
      2. 6.3.2 Analog Input
        1. 6.3.2.1 Single Ended Input
        2. 6.3.2.2 Differential Input
        3. 6.3.2.3 Analog Input Bandwidth
      3. 6.3.3 Sampling Clock Input
      4. 6.3.4 Voltage Reference
      5. 6.3.5 Over-range (OVR)
      6. 6.3.6 Digital Features
        1. 6.3.6.1 Digital Down Converter
          1. 6.3.6.1.1 Digital Down Converter Data Select
          2. 6.3.6.1.2 Decimation Filter
          3. 6.3.6.1.3 DDC Over-range
          4. 6.3.6.1.4 Output Formatting with Decimation
        2. 6.3.6.2 Digital Comparator
          1. 6.3.6.2.1 Comparator Data Select
          2. 6.3.6.2.2 Comparator High and Low Threshold
          3. 6.3.6.2.3 Comparator Configuration Compare Mode
          4. 6.3.6.2.4 Comparator Event Configuration
        3. 6.3.6.3 Statistics Engine
          1. 6.3.6.3.1 Statistics Engine Data Select
          2. 6.3.6.3.2 Window Configuration
        4. 6.3.6.4 Digital Alerts
      7. 6.3.7 Digital Interface
        1. 6.3.7.1 Parallel CMOS Output
        2. 6.3.7.2 Serialized CMOS Output
      8. 6.3.8 Test Patterns
        1. 6.3.8.1 Bypass Test Pattern
        2. 6.3.8.2 Digital Test Pattern
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Power Down Options
    5. 6.5 Programming
      1. 6.5.1 Configuration using the SPI interface
        1. 6.5.1.1 Register Write
        2. 6.5.1.2 Register Read
    6. 6.6 Register Maps
      1. 6.6.1 Register Descriptions
      2. 6.6.2 Statistics Engine Register Map
      3. 6.6.3 Alerts Register Map
  8. 7 Application Information Disclaimer
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Input Signal Path
        2. 7.2.2.2 Sampling Clock
        3. 7.2.2.3 Voltage Reference
      3. 7.2.3 Application Curves
    3. 7.3 Initialization Set Up
      1. 7.3.1 Register Initialization During Operation
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
      2. 7.5.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.2.1 Design Requirements

Frequency domain applications cover a wide range of frequencies from low input frequencies at or near DC in the 1st Nyquist zone to under sampling in higher Nyquist zones. If a low input frequency is supported, then the input has to be DC coupled and the ADC driven by a fully differential amplifier (FDA). If low frequency support is not needed, then AC coupling and use of a balun may be more suitable.

The internal reference is used since DC precision is not needed. However, the ADC AC performance is highly dependent on the quality of the external clock source. If in-band interferes can be present, then the ADC SFDR performance is a key care about as well. A higher ADC sampling rate is desirable to relax the external anti-aliasing filter. An internal decimation filter can be used to reduce the digital output rate afterwards.

Table 7-1 Design key care abouts
FEATURE DESCRIPTION
Signal Bandwidth DC to 30MHz
Input Driver Single ended to differential signal conversion and DC coupling
Clock Source External clock with low jitter

When designing the amplifier/filter driving circuit, the ADC input full-scale voltage needs to be taken into consideration. For example, the ADC3910D125 input full-scale is 1.9 VPP. When factoring in approximately 1dB for insertion loss of the filter, then the amplifier needs to deliver close to 2.1 VPP. The amplifier distortion performance degrades with a larger output swing and considering the ADC common mode input voltage the amplifier may not be able to deliver the full swing. The ADC3910D125 provides an output common mode voltage of 1.25V and the THS4541 for example can only swing within 250mV of its negative supply. A unipolar 3.3V amplifier power supply limits the maximum voltage swing to approximately 2.8 VPP. Hence, if a larger output swing is required (factoring in filter insertion loss) then a negative supply for the amplifier is needed in order to eliminate that limitation. Additionally, input voltage protection diodes may be needed to protect the ADC from over-voltage events.

Table 7-2 Output voltage swing of THS4541 vs power supply
DEVICE MIN OUTPUT VOLTAGE MAX SWING WITH 3.3V/ 0V SUPPLY
THS4541 VS- + 250mV 2.8 VPP