GS9024 Data Sheet
When the signal strength decreases to the level set at the "Carrier Detect
Threshold Adjust" pin, the SSI/CD voltage goes to a logic "0" state (0.8V) and can
be used to drive other TTL/CMOS compatible logic inputs. In addition, when loss
of carrier is detected the SDO/SDO outputs are muted (set to a known static state).
5
4
3
CD_ADJ
CONTROL RANGE
2
1
0
500
150 200
250 300 350 400 450
0
50
100
CABLE LENGTH (m)
5.3 Carrier Detect Threshold Adjust
The threshold level at which loss of carrier is detected is adjustable via external
resistors at the CD_ADJ pin. The control voltage at the CD_ADJ pin is set by a
simple resistor divider circuit. The threshold level is adjustable from 200m to 350m.
By default (no external resistors), the threshold is typically 320m. Connecting this
pin to Ground disables the SDO/SDO muting function and allows for maximum
possible cable length equalization.
This feature is designed for use in applications such as routers where signal
crosstalk and circuit noise cause the equalizer to output erroneous data when no
input signal is present. This problem is not solved by using a Carrier Detect function
with a fixed internal reference because the signal to noise ratio on the circuit board
may be significantly less than the default signal detection level set by the on- chip
reference. To solve this problem, the GS9024 provides a user adjustable threshold
to meet the unique conditions that exist in each user's application. Override and
internal default settings are provided to give the user total flexibility.
5.4 Output Eye Monitor
The GS9024 provides an 'Output Eye Monitor' (OEM) which allows the verification
of signal integrity after equalization, prior to reslicing. The OEM pin is an open
collector current output that requires an external 50Ω pullup resistor. When the
pullup resistor is not used, the OEM block is disabled and the internal OEM circuit
is powered down. The OEM provides a 0.25Vp-p signal when driving a 50Ω
oscilloscope input.
521-70-10 February 2005
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GENNUM [ GENNUM CORPORATION ]
