82V3012 Datasheet, PDF (14/32 Pages) Integrated Device Technology – T1/E1/OC3 WAN PLL WITH DUAL REFERENCE INPUTS

IDT82V3012
Fraction_C19
Fraction_T1
Fraction_C6
T1/E1/OC3 WAN PLL WITH DUAL REFERENCE INPUTS
Output Interface
19.44 MHz _APLL 155.52 MHz
C19_Divider
24.704 MHz
T1_Divider
32.768 MHz
E1_Divider
25.248 MHz
C6_Divider
Fx_sel1 Fx_sel0 (x = 0 or 1)
C2/C1.5
C19POS
C19NEG
C19o
F19o
C1.5o
C3o
C2o
C4o
C8o
C16o
C32o
F0o
F8o
F16o
F32o
RSP
TSP
C6o
Loop Filter
Limiter
Phase ^{Feedback Signal}
Detector
Frequency
Selection
Circuit 1
Frequency
Selection
Circuit 0
FLOCK
Virtual Reference IN_sel F1_sel1 F1_sel0
F0_sel1 F0_sel0
Figure - 7 DPLL Block Diagram
In the Normal mode, the Limiter receives the error signal from the
Phase Detector, limits the phase slope within 5 ns per 125 µs and sends
the limited signal to the Loop Filter.
In the Fast Lock mode, the Limiter is disabled, and the DPLL locks to
the input reference within 500 ms, which is much shorter than that in the
Normal mode.
2.7.3
LOOP FILTER
The Loop Filter ensures that the jitter transfer meets the ETS 300
011 and AT&T TR62411 requirements. It works similarly to a first order
low pass filter with 2.1 Hz cutoff frequency for the four valid input
frequencies (8 kHz, 1.544 MHz, 2.048 MHz or 19.44 MHz).
The output of the Loop Filter goes to the Digital Control Oscillator
directly or through the Fraction blocks, in which E1, T1, C6 and C19
signals are generated.
2.7.4
FRACTION BLOCK
By applying some algorithms to the incoming E1 signal, the
Fraction_C19, Fraction_C6 and Fraction_T1 blocks generate C19, C6
and T1 signals respectively.
2.7.5
DIGITAL CONTROL OSCILLATOR (DCO)
In the Normal mode, the DCO receives four limited and filtered
signals from Loop Filter or Fraction blocks. Based on the values of the
received signals, the DCO generates four digital outputs: 19.44 MHz,
25.248 MHz, 32.768 MHz and 24.704 MHz for C19, C6, E1 and T1
dividers respectively.
In the Holdover mode, the DCO is running at the same frequency as
that generated by storage techniques.
In the Freerun mode, the DCO is running at the same frequency as
that of the master clock.
2.7.6
LOCK INDICATOR
If the output frequency of the DPLL is identical to the input frequency,
and the input phase offset is small enough so that no slope limiting is
exhibited, the LOCK pin will be set high.
2.7.7
OUTPUT INTERFACE
The Output Interface uses three output signals from the DCO to
generate totally 9 types of clock signals and 7 types of framing signals
All these output signals are synchronous to F8o.
Functional Description
14
February 6, 2009