zl30407qcc Zarlink Semiconductor, zl30407qcc Datasheet - Page 12

• Manufacturer Part Number: zl30407qcc
• Description: Sonet/sdh Network Element Pll
• Manufacturer: Zarlink Semiconductor

3.0
The ZL30407 is a Network Element PLL designed to provide timing for SDH and SONET equipment conforming to
ITU-T, ANSI, ETSI and Telcordia recommendations. In addition, it generates clocks for legacy PDH equipment
operating at DS1, DS2, DS3, E1, and E3 rates. The ZL30407 provides clocks for industry standard ST-BUS and
GCI backplanes, and it also supports H.110 timing requirements. The functional block diagram of the ZL30407 is
shown in the “Functional Block Diagram” on page 1 and its operation is described in the following sections.
3.1
The ZL30407 has two Acquisition PLLs for monitoring the availability and quality of the Primary (PRI) and
Secondary (SEC) reference clocks. Each Acquisition PLL operates independently and locks to the falling edges of
one of the three input reference frequencies: 8 kHz, 1.544 MHz, 2.048 MHz or to the rising edges of 19.44 MHz.
The reference frequency is continuously measured and its current frequency can be determined from reading the
Acquisition PLL Status Register bits InpFreq1 and InpFreq0 (see Table 17 "Primary Acquisition PLL Status Register
(R)" and Table 18 "Secondary Acquisition PLL Status Register (R)").
The Primary and Secondary Acquisition PLLs are designed to provide status information that identifies two levels of
reference clock quality. For clarity, only the Primary Acquisition PLL is referenced in the text, but the same applies
to the Secondary Acquisition PLL.
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Outputs of both Acquisition PLLs are connected to a multiplexer (MUX), which allows selection of the desired
reference. This multiplexer channels binary words to the Core PLL digital phase detector (instead of analog signals)
which eliminates quantization errors and improves phase alignment accuracy. The bandwidth of the Acquisition
PLL is much wider than the bandwidth of the following Core PLL. This feature allows cascading Acquisition and
Core PLLs without altering the transfer function of the Core PLL.
3.2
The most critical element of the ZL30407 is its Core PLL, which generates a phase-locked clock, filters jitter and
wander and suppresses input phase transients. All of these features are in agreement with international standards:
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The Core PLL supports three mandatory modes of operation: Free-run, Normal (Locked) and Holdover. Each of
these modes places specific requirements on the building blocks of the Core PLL.
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Reference frequency drifts more than r12 ppm. In response, the PRIOR (Primary Reference Out of Range)
bit and pin change state to high, in conformance with Stratum 3 requirements defined in GR-1244-CORE.
The PRIOR bit is part of Status Register 1 (Table 7 "Status Register 1 (R)").
Reference frequency drifted more than r30000 ppm or that the reference has been lost completely. In
response, the Primary Acquisition PLL enters its own Holdover mode and indicates this by asserting the
HOLDOVER bit in the Primary Acquisition PLL Status Register (Table 17 "Primary Acquisition PLL Status
Register (R)"). Entry into Holdover forces the Core PLL into the Auto Holdover state.
G.813 Option 1 and 2 clocks for SDH equipment
GR-253 for SONET Stratum 3 and SONET Minimum Clocks (SMC)
GR-1244 for Stratum 3 Clock
In Free-run Mode, the Core PLL derives its output clock from the 20 MHz Master Clock Oscillator connected
to pin C20i. The stability of the generated clocks remain the same as the stability of the Master Clock
Oscillator.
In Normal Mode, the Core PLL locks to one of the Acquisition PLLs. Both Acquisition PLLs provide
preprocessed phase data to the Core PLL including detection of reference clock quality.
In Holdover mode, the Core PLL generates a clock based on data collected from past reference signals. The
Core PLL enters Holdover mode if the attached Acquisition PLL switches into the Holdover state or under
external software or hardware control.
Acquisition PLLs
Core PLL
Functional Description
Zarlink Semiconductor Inc.
ZL30407
12
Data Sheet