pt7a4402b Pericom Technology Inc, pt7a4402b Datasheet - Page 15

• Manufacturer Part Number: pt7a4402b
• Description: T1/e1 System Synchronizer
• Manufacturer: Pericom Technology Inc

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A simple way to control the Guard Time is shown in Figure 10.
The Guard Time can be calculated as follows:
* V
input, see DC Electrical Characteristics.
PT0100(12/05)
Figure 12. Timing Example of Unsymmetrical Guard Time Circuit in Automatic Mode
Figure 10. Symmetrical Guard Time Circuit
SIH
is the logic high going threshold for the GTi Schmitt Trigger
PT7A4402B/4402L
t
Gd
= RC x ln (
SEC
Signal
Status
LOS2
PRI
Signal
Status
LOS1
GTo
GTi
PT7A4402B
/4402L State
GTo
GTi
V
CC
V
150kΩ
- V
CC
R
V
SIH
Good
Normal
SIH
1kΩ
PRI
) ≅ RC x 0.6
R
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 11. This setting ensures that reference
switching does not occur until the entire guard time has ex-
pired. The timing diagram is shown in Figure 12.
Figure 11. Unsymmetrical Guard Time Circuit
Holdover
Good
PT7A4402B/4402L
PRI
T
D
Bad
GTi
GTo
T1/E1 System Synchronizer
150kΩ
Normal
1kΩ
R
R
SEC
D
C
1kΩ
PT7A4402B/4402L
R
P
Good
Normal
Data Sheet
PRI
+
10µF
C
Ver:1