SNLS247H April   2007  – June 2016 LMH0302

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 - DC
    6. 6.6 Electrical Characteristics - AC
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Input Interfacing
      2. 7.3.2 Output Interfacing
      3. 7.3.3 Output Slew Rate Control
      4. 7.3.4 Output Enable
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 General Guidance for All Applications
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The LMH0302 is a single-channel SDI cable driver that supports different application spaces. The following sections describe the typical use cases and common implementation practices.

8.1.1 General Guidance for All Applications

The SMPTE specifications define the use of AC-coupling capacitors for transporting uncompressed serial data streams with heavy low-frequency content. This specification requires the use of a 4.7-µF AC-coupling capacitor to avoid low frequency DC wander. The 75-Ω signal is also required to meet certain rise and fall timing to facilitate highest eye opening for the receiving device.

SMPTE specifies the requirements for the Serial Digital Interface to transport digital video at SD, HD, 3 Gbps, and higher data rates over coaxial cables. One of the requirements is meeting the required return loss. This requirement specifies how closely the port resembles 75-Ω impedance across a specified frequency band. Output return loss is dependent on board design. The LMH0302 supports these requirements.

8.2 Typical Application

LMH0302 20214602.gif Figure 3. Application Circuit

8.2.1 Design Requirements

For the LMH0302 design example, Table 1 lists the design parameters.

Table 1. LMH0302 Design Parameters

PARAMETER REQUIREMENT
Input termination Required; 49.9 Ω are recommended (see Figure 3).
Output AC-coupling capacitors Required; both SDO and SDO require AC-coupling capacitors. SDO AC-coupling capacitors are expected to be 4.7 µF to comply with SMPTE wander requirement.
DC power supply coupling capacitors To minimize power supply noise, place 0.1-µF capacitor as close to the device VCC pin as possible.
Distance from device to BNC Keep this distance as short as possible.
High speed SDI and SDI trace impedance Design differential trace impedance of SDI and SDI with 100 Ω.
High speed SDO and SDO trace impedance Single-ended trace impedance for SDO and SDO with 75 Ω.

8.2.2 Detailed Design Procedure

The following design procedure is recommended:

  1. Select a suitable power supply voltage for the LMH0302. It can be powered from a single 3.3-V supply.
  2. Check that the power supply meets the DC requirements in Electrical Characteristics – DC.
  3. Select the proper pull-high or pull-low for SD/HD to set the slew rate.
  4. Select proper pull-high or pull-low for ENABLE to enable or disable the output driver.
  5. Choose a high-quality 75-Ω BNC that is capable to support 2.97-Gbps applications. Consult a BNC supplier regarding insertion loss, impedance specifications, and recommended BNC footprint for meeting SMPTE return loss requirements.
  6. Choose small 0402 surface-mount ceramic capacitors for the AC-coupling and bypass capacitors.
  7. Use proper footprint for BNC and AC-coupling capacitors. Anti-pads are commonly used in power and ground planes under these landing pads to achieve optimum return loss.

8.2.3 Application Curves

LMH0302 lmh0302_sd_sdo.gif Figure 4. SDO PRBS10 at 270 Mbps
LMH0302 C001_SNLS285.png Figure 5. SDO Amplitude vs RREF Resistance