cx28380 Mindspeed Technologies, cx28380 Datasheet - Page 23

• Manufacturer Part Number: cx28380
• Description: Cn8380 Quad T1/e1 Line Interface
• Manufacturer: Mindspeed Technologies

2.3
2.3.1
The received signal is applied to inputs RTIP(n) and RRING(n) through an external termination network as
illustrated in
a noise filter capacitor (0.1
optional, but are recommended for current limiting during lightning surge tests and to maintain a high impedance to
the T1/E1 line if a signal is applied when device power is off. The noise capacitor is also optional, but is
recommended to reduce common mode noise and fast transient noise.
Figure 2-3.
The value of R
is:
The 4 multiplier is due to the 2:1 transformer.
Bipolar AMI pulses are input on the receiver input pins, RTIP[n] and RRING[n]. The receiver recovers clock and
data from the AMI signal which has been attenuated and distorted due to the line characteristics. The AMI pulses
are converted into bipolar or unipolar, NRZ data and output on RPOSO[n] and RNEGO[n], along with the recovered
clock on RCKO[n].
the data outputs. This section discusses each receiver block from the line input to the digital outputs.
29380-DSH-001-B
Receive Line Type
T1 (100 Ω twisted pair)
E1 (120 Ω twisted pair)
E1 (75 Ω coax)
Rx RING
Rx TIP
Figure
t
Receiver Termination Network
is chosen to produce the required receiver input impedance. For the circuit shown, the calculation
Receiver
Receive Termination
Figure 2-4
2-3. The termination network consists of 5.6
5.6
5.6
Preliminary Information / Mindspeed Proprietary and Confidential
µ
Transformer
F), a termination resistor (R
(desired input resistance) = 5.6 + 5.6 + R
R
22.2
27.2
15.9
illustrates the relationship between the AMI received signal, the recovered clock, and
t
2:1
(
Ω
)
0.1
Mindspeed Technologies
Rt
100
100
t
), and 100
RTIP
RRING
Ω
CX28380
line-feed resistors, a 2:1 turns ratio transformer,
Ω
®
protection resistors. The 100
100048_002
t
* 4
Circuit Description
Ω
resistors are
15