SBASB21 September   2024 DDS39RF12 , DDS39RFS12

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 - DC Specifications
    6. 6.6  Electrical Characteristics - AC Specifications
    7. 6.7  Electrical Characteristics - Power Consumption
    8. 6.8  Timing Requirements
    9. 6.9  Switching Characteristics
    10. 6.10 SPI and FRI Timing Diagrams
    11. 6.11 Typical Characteristics: Single Tone Spectra
    12. 6.12 Typical Characteristics: Dual Tone Spectra
    13. 6.13 Typical Characteristics: Power Dissipation and Supply Currents
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 DAC Output Modes
        1. 7.3.1.1 NRZ Mode
        2. 7.3.1.2 RTZ Mode
        3. 7.3.1.3 RF Mode
        4. 7.3.1.4 DES Mode
      2. 7.3.2 DAC Core
        1. 7.3.2.1 DAC Output Structure
        2. 7.3.2.2 Full-Scale Current Adjustment
      3. 7.3.3 DEM and Dither
      4. 7.3.4 Offset Adjustment
      5. 7.3.5 Clocking Subsystem
        1. 7.3.5.1 SYSREF Frequency Requirements
        2. 7.3.5.2 SYSREF Position Detector and Sampling Position Selection (SYSREF Windowing)
      6. 7.3.6 Digital Signal Processing Blocks
        1. 7.3.6.1 Digital Upconverter (DUC)
          1. 7.3.6.1.1 Interpolation Filters
          2. 7.3.6.1.2 Numerically Controlled Oscillator (NCO)
            1. 7.3.6.1.2.1 Phase-Continuous NCO Update Mode
            2. 7.3.6.1.2.2 Phase-coherent NCO Update Mode
            3. 7.3.6.1.2.3 Phase-sync NCO Update Mode
            4. 7.3.6.1.2.4 NCO Synchronization
              1. 7.3.6.1.2.4.1 JESD204C LSB Synchonization
            5. 7.3.6.1.2.5 NCO Mode Programming
          3. 7.3.6.1.3 Mixer Scaling
        2. 7.3.6.2 Channel Bonder
        3. 7.3.6.3 DES Interpolator
      7. 7.3.7 JESD204C Interface
        1. 7.3.7.1  Deviation from JESD204C Standard
        2. 7.3.7.2  Transport Layer
        3. 7.3.7.3  Scrambler and Descrambler
        4. 7.3.7.4  Link Layer
        5. 7.3.7.5  Physical Layer
        6. 7.3.7.6  Serdes PLL Control
        7. 7.3.7.7  Serdes Crossbar
        8. 7.3.7.8  Multi-Device Synchronization and Deterministic Latency
          1. 7.3.7.8.1 Programming RBD
        9. 7.3.7.9  Operation in Subclass 0 Systems
        10. 7.3.7.10 Link Reset
      8. 7.3.8 Alarm Generation
    4. 7.4 Device Functional Modes
      1. 7.4.1 DUC and DDS Modes
      2. 7.4.2 JESD204C Interface Modes
        1. 7.4.2.1 JESD204C Interface Modes
        2. 7.4.2.2 JESD204C Format Diagrams
          1. 7.4.2.2.1 16-bit Formats
      3. 7.4.3 NCO Synchronization Latency
      4. 7.4.4 Data Path Latency
    5. 7.5 Programming
      1. 7.5.1 Using the Standard SPI Interface
        1. 7.5.1.1 SCS
        2. 7.5.1.2 SCLK
        3. 7.5.1.3 SDI
        4. 7.5.1.4 SDO
        5. 7.5.1.5 Serial Interface Protocol
        6. 7.5.1.6 Streaming Mode
      2. 7.5.2 Using the Fast Reconfiguration Interface
      3. 7.5.3 SPI Register Map
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Startup Procedure for DUC/Bypass Mode
      2. 8.1.2 Startup Procedure for DDS Mode
      3. 8.1.3 Understanding Dual Edge Sampling Modes
      4. 8.1.4 Eye Scan Procedure
      5. 8.1.5 Pre/Post Cursor Analysis Procedure
      6. 8.1.6 Sleep and Disable Modes
    2. 8.2 Typical Application
      1. 8.2.1 S-Band Radar Transmitter
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
      4. 8.2.4 Detailed Clocking Subsystem Design Procedure
        1. 8.2.4.1 Example 1: SWAP-C Optimized
        2. 8.2.4.2 Example 2: Improved Phase Noise LMX2820 with External VCO
        3. 8.2.4.3 Example 3: Discrete Analog PLL for Best DAC Performance
        4. 8.2.4.4 10GHz Clock Generation
      5. 8.2.5 Application Curves
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 Power Up and Down Sequence
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines and Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.1.6 Sleep and Disable Modes

There are several methods to power down or temporarily disable the DAC outputs. To prevent asymmetric aging of the device circuits, in some options a low level output from the DACs is maintained. Table 8-1 lists the options for sleep or disabling the DAC outputs.

The most power is saved in full power down, which is enable by setting the MODE register to 0x3. In this mode a low level output signal is maintained to prevent asymmetric aging. Returning to full operation from full power down takes 100's of microseconds.

One or both DAC outputs can be disabled by setting the corresponding MXMODE register to 0x6. This saves some power and the DAC outputs a low level signal to prevent asymmetric aging. If only one channel is disabled, low level spurs from the disabled channel can feed into the active channel, creating spurs around -80 dBFS.

The TX ENABLE function, either through the TXEN0/1 balls or TX_EN registers, provides a method to quickly disable the DAC output by forcing the digital code to 0 (midscale) (see Section 6.9 for the TX ENABLE latency). When the QUITE_TX_ENABLE register is 0, a low level signal is still maintained at the output to prevent saturation. When QUITE_TX_ENABLE is 1, if data independent DEM and Dither is enable, this prevents asymmetric aging. If DEM and dither are disabled or DEM is set to data dependent DEM, the DAC can degrade over the lifetime of the device if a significant faction of the lifetime is spent in this mode. The degradation is channel specific, only affecting the channel that is disabled.

Table 8-1 DAC Sleep and Output Disable Options
Option MXMODE TX_EN QUIET_TX_DISABLE DEM DITHER Low level output long term degradation Power Savings
Device Full Power Down (MODE = 0b11) - - - - - yes no Most
DAC disable 6 1 - - - yes no Some
TX Enable any 0 0 - - yes no Least
TX Enable 0-5 0 1 0,1 0,1 no no Least
TX Enable 0-5 0 1 2, 3 3 no yes Least
TX Enable 6 0 1 0,1 0,1 no no Least
TX Enable 6 0 1 2,3 3 no yes Least

When the DAC is in full power down, the common mode voltage at the DAC output during sleep needs to be maintained below 2V. For AC coupled outputs, the bias is usually provided by an inductor or a balun center tap to 1.8V which forces the common mode also to 1.8V. For DC coupled output, which are typically terminated through a resistor to a voltage above 1.8V (for example, 2.3V), sufficient DAC output current must be provided to reduce the common mode voltage to less than 2V. This is achieved by programming DACx_CBIAS_SLEEP (Address 0x724 bits 7:4 for DACA and Address 0x726 bits 7:4 for DACB) according to the following equation:

Equation 4. D A C _ C B I A S _ S L E E P   =   c e i l   ( 2 ∙ V B I A S - V O U T _ C M _ S L E E P R T E R M   -   7.36 m A 1.47 m A )

where:

  • VOUT_SLEEP is the DAC output common mode in sleep (≤ 2V)
  • VBIAS is the external DC bias
  • RTERM is the external bias resistor/termination to VBIAS
  • ceil is the ceiling operator (integer round up)