MT9044AP datasheet(17/30 Pages) MITEL

17 / 30 page

Advance Information

MT9044

Figure 12 - Unsymmetrical Guard Time

Circuit

Figure 13 shows a typical timing example of an

unsymmetrical Guard Time Circuit with the MT9044

in Automatic Control.

TIE Correction (using GTi)

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

Manual

Control,

since

Automatic

Control

together

with

the

Guard

Time

Circuit

inherently operate in this manner.

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.

•

0.05ppm is the accuracy of Holdover Mode

•

50ns is the maximum phase continuity of the

MT9044 from Normal Mode to Holdover Mode

•

200ns is the maximum phase continuity of the

MT9044 from Holdover Mode to Normal Mode (with

or without TIE Corrector Circuit)

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.

Ω

GTi

10uF

150k

Ω

MT9044

GTo

Ω

Phase

hold

0.05 ppm

100ns

Phase

state

50ns

200ns

250ns

Phase

250ns

100ns

()

3.5us

Figure 13 - Automatic Control, Unsymmetrical Guard Time Circuit Timing Example

PRI

NORMAL

SEC

NORMAL

PRI

HOLDOVER

PRI

NORMAL

LOS2

GOOD

PRI

SIGNAL

STATUS

SEC

SIGNAL

STATUS

LOS1

PRI

NORMAL

PRI

HOLDOVER

BAD

GOOD

BAD

GOOD

GTo

GTi

MT9044

STATE

VSIH

NOTES:

1. TD represents the time delay from when the reference goes

bad to when the MT9044 is provided with a LOS indication.

MT9044AP Datasheet(PDF) 17 Page - Mitel Networks Corporation

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