GS9024 データシートの表示（PDF） - Unspecified
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GS9024 Datasheet PDF : 8 Pages
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5. I/O DESCRIPTION
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5.1. High Speed Analog Inputs (SDI/SDI)
4
SDI/SDI are high impedance inputs which accept
differential or single-ended input drive.
3
CD_ADJ
Figure 12 shows the recommended interface when a single-
CONTROL RANGE
ended serial digital signal is used.
2
1
0
0 50 100 150 200 250 300 350 400 450 500
CABLE LENGTH (m)
Fig. 11
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.
10nF
75Ω
75Ω
10nF
37.5Ω 75Ω
Fig. 12
SDI
GS9024
SDI
5.2. High Speed Outputs (SDO/SDO)
SDO/SDO are current mode outputs that require external
pullups (see Figure 13). The output signal swings are
800mV when 75Ω resistors are used. A diode can be
placed between VCC and the pullups to shift the signal
levels down by approximately 0.7 volts. When the output
traces are longer than 1 inch, controlled impedance traces
should be used. The pullup resistors should be placed at
the end of the output traces as they terminate the trace in
its characteristic impedance (75Ω).
VCC
SDO
GS9024
SDO
75Ω
75Ω
Fig. 13
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.
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GENNUM CORPORATION
521 - 70 - 06
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