GS9024 Data Sheet

521-70-10

February 2005

12 of 16

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).

5.3 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 50

Ω 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 5

0Ω

oscilloscope input.

0

1

2

3

4

5

50

100

150

200

250

300

350

400

450

500

CABLE LENGTH (m)

0

CD_ADJ

CONTROL RANGE