SBAS988 November   2023 ADC34RF55

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 (Dither DISABLED)
    8. 5.8  Electrical Characteristics - AC Specifications (Dither ENABLED)
    9. 5.9  Timing Requirements
    10. 5.10 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Analog Inputs
        1. 6.3.1.1 Input Bandwidth and Full-Scale
        2. 6.3.1.2 Input Imbalance
        3. 6.3.1.3 Over Range Indication
        4. 6.3.1.4 Analog out-of-band dither
      2. 6.3.2 Sampling Clock Input
      3. 6.3.3 ADC Foreground Calibration
        1. 6.3.3.1 Calibration Control
        2. 6.3.3.2 ADC Switch
        3. 6.3.3.3 Calibration Configuration
      4. 6.3.4 SYSREF
        1. 6.3.4.1 SYSREF Capture Detection
      5. 6.3.5 Decimation Filter
        1. 6.3.5.1 Decimation Filter Response
        2. 6.3.5.2 Decimation Filter Configuration
        3. 6.3.5.3 20-bit Output Mode
        4. 6.3.5.4 Numerically Controlled Oscillator (NCO)
        5. 6.3.5.5 NCO Frequency Programming Using the SPI Interface
        6. 6.3.5.6 Fast Frequency Hopping
          1. 6.3.5.6.1 Fast frequency hopping using the GPIO1/2 pins
          2. 6.3.5.6.2 Fast frequency hopping using GPIO1/2, SEN and SDATA pins
          3. 6.3.5.6.3 Fast frequency hopping using the fast SPI
      6. 6.3.6 JESD204B Interface
        1. 6.3.6.1 JESD204B Initial Lane Alignment (ILA)
          1. 6.3.6.1.1 SYNC Signal
        2. 6.3.6.2 JESD204B Frame Assembly
          1. 6.3.6.2.1 JESD204B Frame Assembly in Bypass Mode
          2. 6.3.6.2.2 JESD204B Frame Assembly with Real Decimation - Single Band
          3. 6.3.6.2.3 JESD204B Frame Assembly with Complex Decimation - Single Band
          4. 6.3.6.2.4 JESD204B Frame Assembly with Decimation - Dual Band
        3. 6.3.6.3 SERDES Output MUX
      7. 6.3.7 Test Pattern
        1. 6.3.7.1 Transport Layer
        2. 6.3.7.2 Link Layer
        3. 6.3.7.3 Internal Capture Memory Buffer
    4. 6.4 Device Functional Modes
      1. 6.4.1 Bypass Mode
      2. 6.4.2 Digital Averaging
    5. 6.5 Programming
      1. 6.5.1 GPIO Pin Control
      2. 6.5.2 Configuration using the SPI interface
        1. 6.5.2.1 Register Write
        2. 6.5.2.2 Register Read
    6. 6.6 Register Maps
      1. 6.6.1 Detailed Register Description
  8. 7 Application Information Disclaimer
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Wideband RF Sampling Receiver
      2. 7.2.2 Design Requirements
        1. 7.2.2.1 Input Signal Path
        2. 7.2.2.2 Clocking
      3. 7.2.3 Detailed Design Procedure
        1. 7.2.3.1 Sampling Clock
      4. 7.2.4 Application Curves
    3. 7.3 Initialization Set Up
      1. 7.3.1 Initial Device Configuration After Power-Up
        1. 7.3.1.1  STEP 1: RESET
        2. 7.3.1.2  STEP 2: Device Configuration
        3. 7.3.1.3  STEP 3: JESD Interface Configuration (1)
        4. 7.3.1.4  STEP 4: SYSREF Synchronization
        5. 7.3.1.5  STEP 5: JESD Interface Configuration (2)
        6. 7.3.1.6  STEP 6: Analog Trim Settings
        7. 7.3.1.7  STEP 7: Calibration Configuration
        8. 7.3.1.8  STEP 8: SYSREF Synchronization
        9. 7.3.1.9  STEP 9: Run Power up Calibration
        10. 7.3.1.10 Step 10: JESD Interface Synchronization
        11. 7.3.1.11 Step 11: NCO Configuration
    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 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

6.3.5.4 Numerically Controlled Oscillator (NCO)

Each digital down-converter (DDC) uses a 48-bit numerically controlled oscillator (NCO) to fine tune the frequency placement prior to the digital filtering. Different NCO frequencies for each DDC are programmed using SPI register writes and the desired NCO frequency can be selected using SPI or the GPIO pins. When using the GPIO pins for NCO frequency control, frequency hopping can be achieved in less than 1 µs. The digital NCO is designed to have a SFDR of at least 100 dB. The number of available, programmable NCO frequencies depends on the number of DDC bands used as shown in Table 6-19.

GUID-20220411-SS0I-DR14-R2SP-ZDGXXFWBBQWM-low.svgFigure 6-38 Phase Coherent NCO Block Diagram
Table 6-19 Available No. of Frequencies per NCO depending on No. of DDCs used
No. of DDCs usedNo. of Frequencies per NCO
14
24

There are two different NCO operating modes available. Phase continuous and infinite phase coherent.

  1. Phase Continuous NCO: During a NCO frequency change, the NCO phase gradually adjusts to the new frequency as shown in Figure 6-39. The dashed line shows the phase of original f1 frequency.
  2. Infinite Phase Coherent NCO: With a phase coherent NCO, all frequencies are synchronized to a single event using SYSREF. This enables an infinite amount of frequency hops without the need to reset the NCO as phase coherency is maintained between frequency hops. This is illustrated in Figure 6-39 (right). When returning to the original frequency f1, the NCO phase appears as if the NCO had never changed frequencies.

GUID-20220408-SS0I-T0J4-GR5J-4LH0XDJ0R0CS-low.svgFigure 6-39 Phase Continuous (left) and Infinite Phase Coherent (right) NCO Frequency Switching

The oscillator generates a complex exponential sequence of:

Equation 1. ejωn (default) or e–jωn

where: frequency (ω) is specified as a signed number by the 48-bit register setting

The complex exponential sequence is multiplied with the real input from the ADC to mix the desired carrier to a frequency equal to fIN + fNCO. The NCO frequency can be tuned from –FS/2 to +FS/2 and is processed as a signed, 2s complement number.

The NCO frequency setting is set by the 48-bit register value given and calculated as:

Equation 2. NCO frequency (0 to + FS/2): NCO = fNCO × 248 / FS
Equation 3. NCO frequency (-FS/2 to 0): NCO = (fNCO + FS) × 248 / FS

where:

  • NCO = NCO register setting (decimal value)
  • fNCO = Desired NCO frequency (MHz)
  • FS = ADC sampling rate (MSPS)

The NCO programming is illustrated with this example:

  • ADC sampling rate FS = 3000 MSPS
  • Desired NCO frequency = 920 MHz

Equation 4. NCO frequency setting = fNCO × 248 / FS = 920 MHz x 248 / 3000 MSPS = 86,318,992,857,935

Table 6-20 shows the register writes to set frequency 1 of NCO1 of DDCA to that frequency:

Table 6-20 Example register writes to change NCO frequency
ADDRDATADESCRIPTION
0x050x08Select DDCAB page
0x1050x4ESet frequency to 920 MHz (86,318,992,857,935)
which is 0x4E81B4E81B4E starting MSB in 0x105.
0x1040x81
0x1030xB4
0x1020xE8
0x1010x1B
0x1000x4E
0x180 0x01 Select phase coherent NCO mode.
0x1810x00Load and update NCO1 with the new frequency.
0x1810x30