SBAS534E July   2011  – January 2016 ADS4249

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. ADS424x, ADS422x Family Comparison
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Electrical Characteristics: ADS4249 (250 MSPS)
    6. 7.6  Electrical Characteristics: General
    7. 7.7  Digital Characteristics
    8. 7.8  LVDS and CMOS Modes Timing Requirements
    9. 7.9  LVDS Timings at Lower Sampling Frequencies
    10. 7.10 CMOS Timings at Lower Sampling Frequencies
    11. 7.11 Serial Interface Timing Characteristics
    12. 7.12 Reset Timing (Only when Serial Interface is Used)
    13. 7.13 Typical Characteristics
      1. 7.13.1 Typical Characteristics: ADS4249
      2. 7.13.2 Typical Characteristics: Contour
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Digital Functions
      2. 8.3.2 Gain for SFDR, SNR Trade-Off
      3. 8.3.3 Offset Correction
      4. 8.3.4 Power-Down
        1. 8.3.4.1 Global Power-Down
        2. 8.3.4.2 Channel Standby
        3. 8.3.4.3 Input Clock Stop
      5. 8.3.5 Output Data Format
    4. 8.4 Device Functional Modes
      1. 8.4.1 Output Interface Modes
        1. 8.4.1.1 Output Interface
        2. 8.4.1.2 DDR LVDS Outputs
        3. 8.4.1.3 LVDS Buffer
        4. 8.4.1.4 Parallel CMOS Interface
        5. 8.4.1.5 CMOS Interface Power Dissipation
        6. 8.4.1.6 Multiplexed Mode of Operation
    5. 8.5 Programming
      1. 8.5.1 Parallel Configuration Only
      2. 8.5.2 Serial Interface Configuration Only
      3. 8.5.3 Using Both Serial Interface and Parallel Controls
      4. 8.5.4 Parallel Configuration Details
      5. 8.5.5 Serial Interface Details
        1. 8.5.5.1 Register Initialization
        2. 8.5.5.2 Serial Register Readout
    6. 8.6 Register Maps
      1. 8.6.1 Serial Register Map
      2. 8.6.2 Description of Serial Registers
        1. 8.6.2.1  Register Address 00h (Default = 00h)
        2. 8.6.2.2  Register Address 01h (Default = 00h)
        3. 8.6.2.3  Register Address 01h (Default = 00h)
        4. 8.6.2.4  Register Address 25h (Default = 00h)
        5. 8.6.2.5  Register Address 29h (Default = 00h)
        6. 8.6.2.6  Register Address 2Bh (Default = 00h)
        7. 8.6.2.7  Register Address 3Dh (Default = 00h)
        8. 8.6.2.8  Register Address 3Fh (Default = 00h)
        9. 8.6.2.9  Register Address 40h (Default = 00h)
        10. 8.6.2.10 Register Address 41h (Default = 00h)
        11. 8.6.2.11 Register Address 42h (Default = 00h)
        12. 8.6.2.12 Register Address 45h (Default = 00h)
        13. 8.6.2.13 Register Address 4Ah (Default = 00h)
        14. 8.6.2.14 Register Address 58h (Default = 00h)
        15. 8.6.2.15 Register Address BFh (Default = 00h)
        16. 8.6.2.16 Register Address C1h (Default = 00h)
        17. 8.6.2.17 Register Address CFh (Default = 00h)
        18. 8.6.2.18 Register Address EFh (Default = 00h)
        19. 8.6.2.19 Register Address F1h (Default = 00h)
        20. 8.6.2.20 Register Address F2h (Default = 00h)
        21. 8.6.2.21 Register Address 2h (Default = 00h)
        22. 8.6.2.22 Register Address D5h (Default = 00h)
        23. 8.6.2.23 Register Address D7h (Default = 00h)
        24. 8.6.2.24 Register Address DBh (Default = 00h)
  9. Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Theory of Operation
      2. 9.1.2 Analog Input
        1. 9.1.2.1 Drive Circuit Requirements
        2. 9.1.2.2 Driving Circuit
      3. 9.1.3 Clock Input
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Analog Input
        2. 9.2.2.2 Common Mode Voltage Output (VCM)
        3. 9.2.2.3 Clock Driver
        4. 9.2.2.4 Digital Interface
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
    1. 10.1 Sharing DRVDD and AVDD Supplies
    2. 10.2 Using DC-DC Power Supplies
    3. 10.3 Power Supply Bypassing
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Grounding
      2. 11.1.2 Exposed Pad
      3. 11.1.3 Routing Analog Inputs
      4. 11.1.4 Routing Digital Inputs
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
        1. 12.1.1.1 Definition of Specifications
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

10 Power Supply Recommendations

The ADS4249 has two power supplies, one analog (AVDD) and one digital (DRVDD) supply. Both supplies have a nominal voltage of 1.8 V. The AVDD supply is noise sensitive and the digital supply is not.

10.1 Sharing DRVDD and AVDD Supplies

For best performance the AVDD supply must be driven by a low-noise linear regulator (LDO) and separated from the DRVDD supply. AVDD and DRVDD can share a single supply but they must be isolated by a ferrite bead and bypass capacitors, in a PI-filter configuration, at a minimum. The digital noise is concentrated at the sampling frequency and harmonics of the sampling frequency and can contain noise related to the sampled signal. When developing schematics, leave extra placeholders for additional supply filtering.

10.2 Using DC-DC Power Supplies

DC-DC switching power supplies can be used to power DRVDD without issue. AVDD can also be powered from a switching regulator. Noise and spurs on the AVDD power supply affect the SNR and SFDR of the ADC and show up near dc and as a modulated component around the input frequency. If a switching regulator is used, then design it to have minimal voltage ripple. Use supply filtering to limit the amount of spurious noise at the AVDD supply pins. Allow for extra placeholders on the schematic for additional filtering. Optimization of filtering in the final system is likely required to achieve the desired performance. The choice of power supply ultimately depends on the system requirements. For instance, if very low phase noise is required, then using a switching regulator is not recommended.

10.3 Power Supply Bypassing

Because the ADS4249 already includes internal decoupling, minimal external decoupling can be used without loss in performance. Note that decoupling capacitors can help filter external power-supply noise; thus, the optimum number of capacitors depends on the actual application. A 0.1-uF capacitor is recommended near each supply pin. The decoupling capacitors must be placed very close to the converter supply pins.