The LMH12x9 receiver features an
adaptive continuous-time linear equalizer (CTLE) and a continuously adaptive three-tap
decision feedback equalizer (DFE).
- CTLE: Compensates for
frequency-dependent loss due to the transmission media prior to the device input. The
CTLE accomplishes this by applying variable gain to the input signal, thereby boosting
higher frequencies more than lower frequencies. The CTLE block extends the signal
bandwidth, restores the signal amplitude, and reduces ISI caused by the transmission
medium. The CTLE adapts once following each signal detection event.
- Three-tap DFE: Works in tandem
with the CTLE to provide additional insertion loss compensation alongside crosstalk and
reflection tolerance. The DFE is continuously-adaptive to compensate for
temperature-related variations in the channel.
Note: The CTLE can be manually
overridden through register control. Manual override is not recommended for data rates
where reclocker is enabled (see
Table 6-5).
Adaptive cable equalization is enabled by
default. The LMH12x9 SDI_input
(SDI_IN, SDI_IN1) has an on-chip 75-Ω termination
to the input common-mode voltage and includes a
series return loss compensation network for
meeting stringent SMPTE return loss requirements.
The cable equalizer is designed with high gain and
low noise circuitry to compensate for the
insertion loss of a coaxial cable (such as Belden
1694A), which is widely used in broadcast video
infrastructures.
Note: Adaptation is not applied for data rate
inputs where the relocker is bypassed (including MADI). When operating with the reclocker
bypassed, the appropriate EQ index must be programmed manually.