cx29600 Mindspeed Technologies, cx29600 Datasheet - Page 48

• Manufacturer Part Number: cx29600
• Description: Optiphytm - M155 Sts-3 Sonet/sdh Multiplexer
• Manufacturer: Mindspeed Technologies

2.0 Functional Description
2.1 Line Interface
2.1.2 Signal Detect Interface
2-4
The LSigDet pin on the CX29600 indicates when the PMD has lost its signal. If
the LSigDet goes low, the CX29600 internally forces its receive data to logic ‘0’
to prevent false framing indications. Designs that do not use the LSigDet input
must tie this pin high and then ensure that they either externally force the receive
data to a logic ‘0’ or detect false framing indications with software.
connected directly to a TTL interface without external components. When using a
single-ended PECL interface, a standard PECL termination of 50 Ω to V
is required for most PMDs. The PECL termination can be implemented by using
the Thevenin equivalent circuit shown in
Figure 2-3. Single-ended PECL Diagram
Note:
The LSigDet pin can be driven by TTL or PECL drivers. The CX29600 can be
The termination network shown is valid for a 3.3 V PMD. For a 5.0 V PMD, please refer
to Figure 5-17.
3.3 V
Signal Detect
(SD)
Mindspeed Technologies
PMD
+3.3 V
R
R
1
2
= 130 Ω
= 82 Ω
™
Figure
LSigDet
2-3.
Vsref
3.3 V
+
–
CX29600
CX29600 Data Sheet
29600-DSH-001-B
Internal
logic
CX29600
cc
– 2 V