TQ8103 데이터 시트보기 (PDF) - TriQuint Semiconductor
부품명
상세내역
제조사
TQ8103 Datasheet PDF : 9 Pages
| |||
TQ8103
Application Information
Loop Filter Design
The TQ8103 requires an external loop filter. Care should
be taken in the implementation of the filter. Good high-
frequency design techniques should be used, with the
loop filter being connected into the analog ground. The
analog supply should be well filtered.
Data Input Considerations
The serial data input line is a high-frequency ECL signal,
and should be kept in a 50 ohm controlled impedance
environment. Reflections on the serial input are
minimized through the use of a separate loopback
termination pin, SINO. A 50 ohm chip resistor between
SINO and VTT minimizes stub length for the best signal
quality. Another physical design consideration is to
place the TQ8103 and its companion high-speed ICs as
close as possible to the optics while observing good
analog design practice on supply filtering and
grounding.
External Frequency Reference
The externally supplied 38.88 MHz CKREF input needs
to have low jitter with fast rise and fall times. Typical
applications will use a telecom crystal oscillator such as
the Connor-Winfield S14R6-38.88. SONET requires freq-
uency sources to be accurate to ±20␣ ppm over temper-
ature, voltage, and aging. The CKREF input is a reference
frequency for initial frequency lock and for the lock-detect
circuit, so it can tolerate accuracies of up to ±100␣ ppm.
Figure 3. External Loop Filter
OUCHP
VCTL
20 KΩ
1000 pF
62 Ω
1 mF
Jitter Tolerance
Jitter tolerance describes the ability of the CDR circuit
to track timing variations (jitter) in the received signal.
The Bellcore and ITU specifications allow the received
optical signal to contain jitter. The amount of jitter that
must be tolerated is a function of the frequency content
of the jitter. The CDR must tolerate many unit intervals
(bit times) of low-frequency jitter, but is not asked to
tolerate large amounts of jitter at higher frequency. The
performance shown in the “Typical Performance Data”
section shows that the TQ8103 offers a wide margin
over the specification limits.
Jitter tolerance is a system-level issue that is directly
affected by the quality of the optics, the quality of the
layout (and decoupling), and the specific
implementation of the loop filter. The recommended
loop filter, described above, has been chosen to provide
a robust margin on jitter tolerance.
For additional information and latest specifications, see our website: www.triquint.com
3
Share Link: 