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The transmitter line driver can be disabled and the TXPn and TXNn outputs tri-stated by asserting the LTS
configuration bit (
PORT.CR2
.LTS). Powering down the transmitter through the TPD configuration bit (CPU bus
mode) also tri-states the TXPn and TXNn outputs.
10.12.4.3 Interfacing to the Line
The transmitter interfaces to the outgoing DS3/E3 coaxial cable (75 ) through a 2:1 step-down transformer
connected to the TXPn and TXNn pins.
Figure 1-1
shows the arrangement of the transformer and other
recommended interface components.
Table 10-33
specifies the required characteristics of the transformer.
10.12.4.4 Transmit Driver Monitor
If the transmit driver monitor detects a faulty transmitter, it sets the
PORT.SR
.TDM status bit. When the transmitter
is tri-stated, the transmit driver monitor is also disabled. The transmitter is declared to be faulty when the
transmitter outputs see a load of less than ~25 .
10.12.4.5 Transmitter Power-Down
To minimize power consumption when the transmitter is not being used, assert the
PORT.CR1
.PD configuration
bit. When the transmitter is powered down, the TXPn and TXNn pins are put in a high-impedance state and the
transmit amplifiers are powered down.
10.12.4.6 Transmitter Jitter Generation (Intrinsic)
The transmitter meets the jitter generation requirements of all applicable standards, with or without the jitter
attenuator enabled.
10.12.4.7 Transmitter Jitter Transfer
Without the jitter attenuator enabled in the transmit side, the transmitter passes jitter through unchanged. With the
jitter attenuator enabled in the transmit side, the transmitter meets the jitter transfer requirements of all applicable
telecommunication standards. See
Table 4-1
.
10.12.5 Receiver
10.12.5.1 Interfacing to the Line
The receiver can be transformer-coupled or capacitor-coupled to the line. Typically, the receiver interfaces to the
incoming coaxial cable (75 ) through a 1:2 step-up transformer.
Figure 1-1
shows the arrangement of the
transformer and other recommended interface components. Table 10-33 specifies the required characteristics of
the transformer.
Figure 10-32
shows a general overview of the LIU block. The receiver expects the incoming signal
to be in B3ZS- or HDB3-coded AMI format.
Table 10-33. Transformer Characteristics
PARAMETER
VALUE
Turns Ratio
1:2ct 2%
Bandwidth 75
0.250MHz to 500MHz (typ)
Primary Inductance
19 H (min)
Leakage Inductance
0.12 H (max)
Interwinding Capacitance
10pF (max)
Isolation Voltage
1500V
RMS
(min)