Overview
The LMH0344SQ/NOPB is a 3-Gbps HD–SD SDI Adaptive Cable Equalizer produced by Texas Instruments. This device is designed to equalize data transmitted over cable or any media with similar dispersive loss characteristics. It operates over a wide range of data rates from 125 Mbps to 2.97 Gbps and supports various SMPTE standards including ST 424, ST 292, ST 344, and ST 259. The LMH0344 ensures reliable transmission of serial digital video signals by compensating for signal degradation caused by cable length and other media losses.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Data Rate Range | 125 Mbps to 2.97 Gbps | |
| Maximum Cable Length (Belden 1694A) | Up to 120m at 2.97 Gbps, up to 140m at 1.485 Gbps, up to 400m at 270 Mbps | m |
| Supply Voltage | 3.3 V | V |
| Power Consumption | 280 mW (typical) | mW |
| Operating Temperature Range | -40 to 85°C | °C |
| Junction Temperature | 125°C | °C |
| Input Configuration | Single-ended or differential | |
| Output Configuration | 50-Ω differential outputs (internal 50-Ω pull-ups) |
Key Features
- Manual bypass and output mute with a programmable threshold
- Separate carrier detect and output mute pins
- Programmable mute reference to mute the output at a selectable level of signal degradation
- DC restoration and level control to handle pathological data conditions
- Automatic equalization control (AEC) with an external capacitor for loop response control
- Single 3.3-V supply operation
- Support for AC-coupling capacitors to avoid low frequency DC wander
Applications
The LMH0344 is primarily used in professional video equipment and broadcast systems to equalize serial digital video signals transmitted over coaxial cables. It is suitable for various applications including:
- High-definition (HD) and standard-definition (SD) video transmission
- Professional video production and broadcasting
- Medical imaging and diagnostic equipment
- Industrial video systems
Q & A
- What is the primary function of the LMH0344?
The LMH0344 is designed to equalize data transmitted over cable or any media with similar dispersive loss characteristics, ensuring reliable transmission of serial digital video signals.
- What data rate range does the LMH0344 support?
The LMH0344 supports data rates from 125 Mbps to 2.97 Gbps.
- What types of input configurations are supported by the LMH0344?
The LMH0344 accepts either single-ended or differential input configurations.
- What is the purpose of the bypass pin on the LMH0344?
The bypass pin allows the adaptive equalizer to be bypassed, disabling equalization and DC restoration.
- How does the LMH0344 handle pathological data conditions?
The LMH0344 incorporates a self-biasing DC restoration circuit to handle pathological data conditions.
- What is the significance of the carrier detect (CD) and mute pins?
The carrier detect pin indicates if a valid signal is present at the input, and the mute pin can be used to mute the output when no signal is present or at a selectable level of signal degradation.
- What are the power supply requirements for the LMH0344?
The LMH0344 operates on a single 3.3-V supply, and the power supply should be designed to provide the recommended operating conditions in terms of DC voltage.
- What are the key considerations for PCB layout when using the LMH0344?
Key considerations include minimizing impedance discontinuities, using surface-mount components, and maintaining symmetry on complementary signals to ensure optimal performance.
- What SMPTE standards does the LMH0344 support?
The LMH0344 supports SMPTE standards ST 424, ST 292, ST 344, and ST 259.
- How does the LMH0344 handle different cable lengths?
The LMH0344 can equalize data transmitted over various cable lengths, such as up to 120 meters of Belden 1694A at 2.97 Gbps, up to 140 meters at 1.485 Gbps, and up to 400 meters at 270 Mbps.
