CN8380 Datasheet, PDF (37/91 Pages) Conexant Systems, Inc – integrated quad line interface unit unit for both 1.544 Mbps (T1) and 2.048 Mbps (E1) applications

CN8380
Quad T1/E1 Line Interface
2.0 Circuit Description
2.4 Transmitter
The standard transformer recommended has a turns ratio of 1:2. This turns
ratio is required if parallel termination (Rt) or series resistors (Rs) are desired.
The alternate transformer has a turns ratio of 1:1.36. This transformer can be used
only if all of the following are true:
• Parallel termination (Rt) is not used.
• Series resistors (Rs) are not used.
• T1 DSX-1 transmit pulse is not used.
Refer to Option E in Table 2-7 below. Transmitter power consumption is
reduced by approximately 30%, compared to the unterminated, standard
transformer configuration.
Resistors (Rs) in series with Tx TIP and Tx RING line connections are
sometimes used with surge protection circuits. Without compensation, the
addition of these resistors decreases the transmit pulse amplitude. The CN8380
provides an option in Host Mode to boost the output level if resistors are installed.
Compensation is optimized for the use of 5.6 Ω Rs values. In Hardware Mode,
these resistors are required.
Figure 2-7. Transmit Termination Components
XTIP
CN8380
Ct
XRING
8380_012
1:N
Rs
Tx TIP
Rt
Rs
Transformer
Tx RING
Tables 2-4 through 2-8 provide recommended termination component values
and CN8380 configuration information for all termination options supported. The
resulting return loss value is also listed. All five options are supported in Host
Mode, whereas only options C and D are supported in Hardware Mode.
Before selecting a termination option, refer to Table 2-3, Transmit Pulse
Configurations, to select an application mode. Then refer to the Transmit
Termination tables below to select a termination option.
N8380DSA
Conexant
2-15
Advance Information