GS2974B GS2974B HD-LINX™ III Adaptive Cable

Equalizer

Data Sheet

45062 - 3

April 2009

11 of 17

does not solve this problem, since the signal to noise ratio on the circuit board could be

significantly less than the default signal detection level set by the on chip reference.

NOTE: MCLADJ is only recommended for data rates up to 360Mb/s. For data rates above

this, MCLADJ should be left floating.

4.4 Mute and Carrier Detect

The GS2974B includes a MUTE input pin that allows the application interface to mute

the Serial Digital Output at any time. Set the MUTE pin HIGH to mute SDO and SDO. In

this case, the outputs will mute regardless of the setting of the BYPASS pin.

A Carrier Detect output pin (CD) indicates the presence of a valid signal at the input of

the GS2974B. When CD is LOW, the device has detected a valid input on SDI and SDI.

When CD is HIGH, the device has not detected a valid input.

NOTE 1: CD will only detect loss of carrier for data rates greater than 19Mb/s. The CD

output pin may be connected directly to the MUTE input pin to enable automatic muting

of the GS2974B when no valid input signal has been detected.

NOTE 2: If the maximum cable length is exceeded (set by the MCLADJ pin) and the

device is not in Bypass mode, the CD pin will not be driven low, even if a carrier is

present.

Table 4-1: Mute Input Table

Mute

Function

0

SDO and SDO operate normally

1

SDO and SDO are forced to a steady

state

Table 4-2: CD Output Table

CD

Input Status

0

Valid Input on SDI, SDI pins

1

Input is not valid