
Features
Meets requirements of Telcordia GR-253-CORE
for SONET internal clocks and GR-1244-CORE
for Stratum 3 clocks
Meets requirements of ITU-T G.813 Option 1
and Option 2 for SDH Equipment Clocks (SEC)
Provides OC-3/STM-1, DS3, E3, 19.44MHz,
DS2, E1, T1, 8kHz and ST-BUS clock outputs
Accepts two independent reference inputs
Selectable 1.544MHz, 2.048MHz, 19.44MHz or
8kHz input reference frequencies
Holdover accuracy of 0.02 ppm
Intrinsic jitter under 200 picoseconds pk-pk
unfiltered on the 19.44MHz and 155.52MHz
clocks
Output clock phase can be trimmed to support
master-slave arrangements
Hardware Mode, or optional Microport Mode
with 8 bit microprocessor port access
3.3V supply
JTAG boundary scan
Applications
SONET/SDH Add/Drop multiplexers
SONET/SDH uplinks
Integrated access devices
ATM edge switches
Description
The MT90401 is a digital phase locked loop (DPLL)
that is designed to synchronize SDH (Synchronous
Digital Hierarchy) and SONET (Synchronous Optical
Network) networking equipment. The MT90401 is
used to ensure that the timing of outgoing signals
remains within the limits specified by Telcordia, ANSI
and the ITU during normal operation and in the
presence
of
disturbances
synchronization signals.
on
the
incoming
The MT90401 can operate in free-run, locked or
holdover mode. The loop filter corner frequency can
be selected to suit SONET applications or to suit SDH
applications. The MT90401 uses an external 20MHz
oscillator as its master clock and it does not require
external loop filter components.
In Hardware Mode, the MT90401 can be controlled
and monitored via external pins. In Microport Mode, a
microprocessor can be used for more comprehensive
control and monitoring.
PB5429
ISSUE 4
January 2001
Ordering Information
MT90401AB
80 Pin LQFP
-40 to +85
°
C
Figure 1 - Functional Block Diagram
Virtual
Reference
Selected
Refer-
ence
IEEE
1149.1a
Reference
Select
Feedback
TIE
Corrector
Enable
Control State Machine
DPLL
State
Select
State
Select
Frequency
Select
MUX
Input
Impairment
Monitor
Output
Interface
Circuit
Reference
Select
MUX
TIE
Corrector
Circuit
MS1 MS2
FS1
FS2
TCK
TDI
TMS
TRST
SEC
RST
RSEL
VDD
VSS
TCLR
C1.5o
C2o
C4o
C6o
C19o
C8o
C16o
C44/C34
F0o
F8o
F16o
TDO
HOLDOVER
FLOCK
LOCK
Reference
Monitor
Prioor
Secoor
D0/D7 A0/A6 CS,DS,R/W
C155P/N
C20i
Master Clock
PCCi
PRI
MT90401
SONET/SDH System Synchronizer
Product Brief