SBOS849B December   2017  – February 2019 LMH5401-SP

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      LMH5401-SP Small Signal Frequency Response
      2.      LMH5401-SP Driving an ADC12D1620QML
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 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: VS = 5 V
    6. 7.6 Electrical Characteristics: VS = 3.3 V
    7. 7.7 Typical Characteristics: 5 V
    8. 7.8 Typical Characteristics: 3.3 V
  8. 8 Parameter Measurement Information
    1. 8.1  Output Reference Nodes and Gain Nomenclature
    2. 8.2  ATE Testing and DC Measurements
    3. 8.3  Frequency Response
    4. 8.4  S-Parameters
    5. 8.5  Frequency Response with Capacitive Load
    6. 8.6  Distortion
    7. 8.7  Noise Figure
    8. 8.8  Pulse Response, Slew Rate, and Overdrive Recovery
    9. 8.9  Power Down
    10. 8.10 VCM Frequency Response
    11. 8.11 Test Schematics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Fully-Differential Amplifier
      2. 9.3.2 Operations for Single-Ended to Differential Signals
        1. 9.3.2.1 AC-Coupled Signal Path Considerations for Single-Ended Input to Differential Output Conversion
        2. 9.3.2.2 DC-Coupled Input Signal Path Considerations for SE-DE Conversions
        3. 9.3.2.3 Resistor Design Equations for Single-to-Differential Applications
        4. 9.3.2.4 Input Impedance Calculations
      3. 9.3.3 Differential-to-Differential Signals
        1. 9.3.3.1 AC-Coupled, Differential-Input to Differential-Output Design Issues
        2. 9.3.3.2 DC-Coupled, Differential-Input to Differential-Output Design Issues
      4. 9.3.4 Output Common-Mode Voltage
    4. 9.4 Device Functional Modes
      1. 9.4.1 Operation With a Split Supply
      2. 9.4.2 Operation With a Single Supply
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Stability, Noise Gain, and Signal Gain
      2. 10.1.2 Input and Output Headroom Considerations
      3. 10.1.3 Noise Analysis
      4. 10.1.4 Noise Figure
      5. 10.1.5 Thermal Considerations
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Driving Matched Loads
        2. 10.2.2.2 Driving Unmatched Loads For Lower Loss
        3. 10.2.2.3 Driving Capacitive Loads
        4. 10.2.2.4 Driving ADCs
          1. 10.2.2.4.1 SNR Considerations
          2. 10.2.2.4.2 SFDR Considerations
          3. 10.2.2.4.3 ADC Input Common-Mode Voltage Considerations—AC-Coupled Input
          4. 10.2.2.4.4 ADC Input Common-Mode Voltage Considerations—DC-Coupled Input
        5. 10.2.2.5 GSPS ADC Driver
        6. 10.2.2.6 Common-Mode Voltage Correction
        7. 10.2.2.7 Active Balun
      3. 10.2.3 Application Curves
    3. 10.3 Do's and Don'ts
      1. 10.3.1 Do:
      2. 10.3.2 Don't:
  11. 11Power Supply Recommendations
    1. 11.1 Supply Voltage
    2. 11.2 Single Supply
    3. 11.3 Split Supply
    4. 11.4 Supply Decoupling
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Device Nomenclature
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

9.3.2.1 AC-Coupled Signal Path Considerations for Single-Ended Input to Differential Output Conversion

When the signal path is ac coupled, the dc biasing for the LMH5401-SP becomes a relatively simple task. In all designs, start by defining the output common-mode voltage. The ac-coupling issue can be separated for the input and output sides of an FDA design. The input can be ac coupled and the output dc coupled, or the output can be ac coupled and the input dc coupled, or they can both be ac coupled. One situation where the output can be dc coupled (for an ac-coupled input), is when driving directly into an ADC where the VOCM control voltage uses the ADC common-mode reference to directly bias the FDA output common-mode to the required ADC input common-mode. The feedback path must always be dc-coupled. In any case, the design starts by setting the desired VOCM. When an ac-coupled path follows the output pins, the best linearity is achieved by operating VOCM at mid supply. The VOCM voltage must be within the linear range for the common-mode loop, as specified in the headroom specifications. If the output path is also ac coupled, simply letting the VOCM control pin float is usually preferred in order to obtain a midsupply default VOCM bias with no external elements. To limit noise, place a 0.1-µF decoupling capacitor on the VOCM pin to ground. After VOCM is defined, check the target output voltage swing to ensure that the VOCM positive or negative output swing on each side does not clip into the supplies. If the desired output differential swing is defined as VOPP, divide by 4 to obtain the ±VP swing around VOCM at each of the two output pins (each pin operates 180° out of phase with the other). Check that VOCM ±VP does not exceed the output swing of this device. Going to the device input pins side, because both the source and balancing resistor on the non-signal input side are dc blocked (see Figure 59), no common-mode current flows from the output common-mode voltage, thus setting the input common-mode equal to the output common-mode voltage. This input headroom also sets a limit for higher VOCM voltages. The minimum headroom for the input pins to the positive supply overrides the headroom limit for the output VOCM because the input VICM is the output VOCM for ac-coupled sources. Also, the input signal moves this input VICM around the dc bias point, as described in the Resistor Design Equations for Single-to-Differential Applications subsection of the Fully-Differential Amplifier section.