MT9046 Zarlink Semiconductor, MT9046 Datasheet - Page 21

• Manufacturer Part Number: MT9046
• Description: T1/E1 System Synchronizer with Holdover
• Manufacturer: Zarlink Semiconductor

t
A digital alternative to the RC-time-constant circuit is presented in Figure 12. The circuit in Figure 12 can be used to
generate a steady lock signal. The circuit monitors the MT9046’s LOCK pin, as long as it detects a positive pulse
every 1.024 seconds or less, the Advanced Lock output will remain high. If no positive pulse is detected on the
LOCK output within 1.024 seconds, the Advanced LOCK output will go low.
D
=
V
- R C ln(V
t
R = Resistor value (3.3 MΩ)
C = Capacitor value (1 µF)
V
Schmitt Trigger (2.0 V)
V
MT9046
D
DD
T-
DD
= Capacitor’s discharge time
= Negative going threshold voltage of the
= 3.3 V
= 3.3 V
T-
/V
MT9046
DD
Lock
) = 1.65 seconds
Figure 12 - Digital Lock Pin Circuit
Figure 11 - Time-constant Circuit
IN4148
R=3.3 M
Zarlink Semiconductor Inc.
MT9046
+
C=1 µf
21
74HC14
74HC14
LOCK
Data Sheet