SBAS840C July   2020  – December 2022 ADC3541 , ADC3542 , ADC3543

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 ADC3541
    8. 6.8  Electrical Characteristics - AC Specifications ADC3542
    9. 6.9  Electrical Characteristics - AC Specifications ADC3543
    10. 6.10 Timing Requirements
    11. 6.11 Typical Characteristics: ADC3541
    12. 6.12 Typical Characteristics: ADC3542
    13. 6.13 Typical Characteristics: ADC3543
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Analog Input
        1. 8.3.1.1 Analog Input Bandwidth
        2. 8.3.1.2 Analog Front End Design
          1. 8.3.1.2.1 Sampling Glitch Filter Design
          2. 8.3.1.2.2 Single Ended Input
          3. 8.3.1.2.3 Analog Input Termination and DC Bias
            1. 8.3.1.2.3.1 AC-Coupling
            2. 8.3.1.2.3.2 DC-Coupling
        3. 8.3.1.3 Auto-Zero Feature
      2. 8.3.2 Clock Input
        1. 8.3.2.1 Single Ended vs Differential Clock Input
        2. 8.3.2.2 Signal Acquisition Time Adjust
      3. 8.3.3 Voltage Reference
        1. 8.3.3.1 Internal voltage reference
        2. 8.3.3.2 External voltage reference (VREF)
        3. 8.3.3.3 External voltage reference with internal buffer (REFBUF)
      4. 8.3.4 Digital Down Converter
        1. 8.3.4.1 Digital Filter Operation
        2. 8.3.4.2 FS/4 Mixing with Real Output
        3. 8.3.4.3 Numerically Controlled Oscillator (NCO) and Digital Mixer
        4. 8.3.4.4 Decimation Filter
        5. 8.3.4.5 SYNC
        6. 8.3.4.6 Output Formatting with Decimation
          1. 8.3.4.6.1 Parallel CMOS
          2. 8.3.4.6.2 Serialized CMOS Interface
      5. 8.3.5 Digital Interface
        1. 8.3.5.1 Parallel CMOS Output
        2. 8.3.5.2 Serialized CMOS output
          1. 8.3.5.2.1 SDR Output Clocking
        3. 8.3.5.3 Output Data Format
        4. 8.3.5.4 Output Formatter
        5. 8.3.5.5 Output Bit Mapper
        6. 8.3.5.6 Output Interface/Mode Configuration
          1. 8.3.5.6.1 Configuration Example
      6. 8.3.6 Test Pattern
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal operation
      2. 8.4.2 Power Down Options
    5. 8.5 Programming
      1. 8.5.1 Configuration using PINs only
      2. 8.5.2 Configuration Using the SPI Interface
        1. 8.5.2.1 Register Write
        2. 8.5.2.2 Register Read
    6. 8.6 Register Map
      1. 8.6.1 Detailed Register Description
  9. 9 Application Information Disclaimer
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Input Signal Path
        2. 9.2.2.2 Sampling Clock
        3. 9.2.2.3 Voltage Reference
      3. 9.2.3 Application Curves
    3. 9.3 Initialization Set Up
      1. 9.3.1 Register Initialization During Operation
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.1 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 undersampling in higher Nyquist zones. If very 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 interferers can be present, then the ADC SFDR performance is a key care about. A higher ADC sampling rate is desirable in order to relax the external anti-aliasing filter – an internal decimation filter can be used to reduce the digital output rate afterwards.

Table 9-1 Design key care-abouts
FEATUREDESCRIPTION
Signal BandwidthDC to 20 MHz
Input DriverSingle ended to differential signal conversion and DC coupling
Clock SourceExternal 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 ADC354x input full-scale is 2.25 Vpp. When factoring in ~ 1 dB for insertion loss of the filter, then the amplifier needs to deliver close to 2.5 Vpp. The amplifier distortion performance will degrade 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 ADC354x provides an output common mode voltage of 0.95 V, and the device can only swing within 250 mV of the negative supply. A unipolar 3.3 V amplifier power supply limits the maximum voltage swing to ~ 2.8 V pp. Additionally, input voltage protection diodes may be needed to protect the ADC from over-voltage events.

Table 9-2 Output voltage swing of THS4541 vs power supply
DEVICEMIN OUTPUT VOLTAGEMAX SWING WITH 3.3 V/ 0 V SUPPLY
THS4541VS- + 250 mV2.8 Vpp