pt7a4409 Pericom Technology Inc, pt7a4409 Datasheet - Page 15

• Manufacturer Part Number: pt7a4409
• Description: T1/e1/oc3 System Synchronizer
• Manufacturer: Pericom Technology Inc

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A simple way to control the Guard Time is shown in Figure 11.
The Guard Time can be calculated as follows:
* V
input, see DC Electrical Characteristics.
PT0103(12/05)
Figure 13. Timing Example of Unsymmetrical Guard Time Circuit in Automatic Mode
Figure 11. Symmetrical Guard Time Circuit
SIH
PT7A4409/4409L
t
is the logic high going threshold for the GTi Schmitt Trigger
Gd
= RC x ln (
SEC
Signal
Status
LOS2
PRI
Signal
Status
LOS1
GTo
GTi
PT7A4409/
4409L State
GTo
GTi
V
V
150kΩ
CC
CC
R
V
- V
Good
Normal
SIH
1kΩ
PRI
R
SIH
) ≅ RC x 0.6
P
Holdover
Bad
+
PRI
10µF
C
T
D
Good
Normal
PRI
15
In cases where fast toggling of the LOS1 input might be ex-
pected, an unsymmetrical Guard Time Circuit is recommended
as shown in Figure 12. This setting ensures that reference
switching does not occur until the entire guard time has ex-
pired. The timing diagram is shown in Figure 13.
Figure 12. Unsymmetrical Guard Time Circuit
PT7A4409/4409L
Holdover
Good
PRI
T
D
T1/E1/OC3 System Synchronizer
Bad
GTi
GTo
150kΩ
Normal
1kΩ
R
R
SEC
D
C
1kΩ
R
P
PT7A4409/4409L
Good
Normal
Data Sheet
PRI
+
10µF
C
Ver:2