Advance Information
MT9044
For instance, 10 Normal to Holdover to Normal mode
change sequences occur, and in each case Holdover
was entered for 2s. Each mode change sequence
could account for a phase change as large as 350ns.
Thus, the accumulated phase change could be as
large as 3.5us, and, the overall MTIE could be as
large as 3.5us.
MT9044
GTo
+
R
C
150kΩ
R
D
1kΩ
C
10uF
Phase
Phase
Phase
= 0.05ppm × 2s = 100ns
= 50ns + 200ns= 250ns
hold
state
GTi
R
P
= 10 × (250ns + 100ns) = 3.5us
1kΩ
10
Figure 12 - Unsymmetrical Guard Time
Circuit
•
•
0.05ppm is the accuracy of Holdover Mode
50ns is the maximum phase continuity of the
MT9044 from Normal Mode to Holdover Mode
Figure 13 shows a typical timing example of an
unsymmetrical Guard Time Circuit with the MT9044
in Automatic Control.
•
200ns is the maximum phase continuity of the
MT9044 from Holdover Mode to Normal Mode (with
or without TIE Corrector Circuit)
TIE Correction (using GTi)
When 10 Normal to Holdover to Normal mode
change sequences occur without MTIE enabled, and
in each case holdover was entered for 2s, each
mode change sequence could still account for a
phase change as large as 350ns. However, there
would be no accumulated phase change, since the
input to output phase is re-aligned after every
Holdover to Normal state change. The overall MTIE
would only be 350ns.
When Primary Holdover Mode is entered for short
time periods, TIE correction should not be enabled.
This will prevent unwanted accumulated phase
change between the input and output. This is mainly
applicable to Manual Control, since Automatic
Control together with the Guard Time Circuit
inherently operate in this manner.
SEC
SIGNAL
STATUS
GOOD
LOS2
PRI
SIGNAL
STATUS
GOOD
GOOD
BAD
GOOD
BAD
T
T
D
D
LOS1
GTo
GTi
V
SIH
MT9044
STATE
PRI
NORMAL
PRI
HOLDOVER
PRI
NORMAL
PRI
HOLDOVER
SEC
NORMAL
PRI
NORMAL
NOTES:
1. T represents the time delay from when the reference goes
D
bad to when the MT9044 is provided with a LOS indication.
Figure 13 - Automatic Control, Unsymmetrical Guard Time Circuit Timing Example
17
MITEL [ MITEL NETWORKS CORPORATION ]
