MT9044AP1 Zarlink Semiconductor, Inc., MT9044AP1 Datasheet - Page 20

• Manufacturer Part Number: MT9044AP1
• Description: Framer: Framer Circuit: T1/E1/OC3 System Synchronizer
• Manufacturer: Zarlink Semiconductor, Inc.

A simple way to control the guard time (using Automatic Control) is with an RC circuit as shown in Figure 11.
Resistor R
guard time can be calculated as follows.
•
In cases where fast toggling might be expected of the LOS1 input, then an unsymmetrical Guard Time Circuit is
recommended. This ensures that reference switching doesn’t occur until the full guard time value has expired. An
unsymmetrical Guard Time Circuit is shown in Figure 12.
V
SIH
is the logic high going threshold level for the GTi Schmitt Trigger input, see DC Electrical Characteristics
P
is for protection only and limits the current flowing into the GTi pin during power down conditions. The
Figure 12 - Unsymmetrical Guard Time Circuit
Figure 11 - Symmetrical Guard Time Circuit
MT9044
MT9044
guard time
guard
example
guard time 150k 10u
GTo
GTo
GTi
GTi
time
Zarlink Semiconductor Inc.
≈
≈
MT9044
=
150kΩ
RC 0.6
150kΩ
1kΩ
RC
R
R
R
C
D
20
×
×
×
ln
1kΩ
R
1kΩ
R



P
--------------------------------
V DD V SIH
P
×
+
0.6
V DD
10uF
–
=
C
0.9s
10uF
C



+
Data Sheet