MT9045 Zarlink Semiconductor, MT9045 Datasheet - Page 19

• Manufacturer Part Number: MT9045
• Description: T1/E1/OC3 System Synchronizer
• Manufacturer: Zarlink Semiconductor

Lock Indicator
The LOCK pin toggles at a random rate when the PLL is frequency locked to the input reference. In Figure 11 the
RC-time-constant circuit can be used to hold the high state of the LOCK pin.
Once the PLL is frequency locked to the input reference, the minimum duration of LOCK pin’s high state would be
32ms and the maximum duration of LOCK pin’s low state would not exceed 1 second. The following equations can
be used to calculate the charge and discharge times of the capacitor.
t
t
C
D
= - R
= - R C ln(V
D
t
R
C = Capacitor value (1µF)
V
Schmitt Trigger (3.0 V)
V
t
R = Resistor value (3.3 MΩ)
C = Capacitor value (1µF)
V
Schmitt Trigger (2.0 V)
V
C
D
C ln(1 – V
T+
DD
T-
DD
D
= Capacitor’s charge time
= Capacitor’s discharge time
= Dynamic resistance of the diode (100 Ω)
= Negative going threshold voltage of the
= Positive going threshold voltage of the
= 3.3 V
= 3.3 V
T-
/V
DD
T+
) = 1.65 seconds
/V
DD
) = 240 µs
Figure 10 - Power-Up Reset Circuit
MT9045
RST
Zarlink Semiconductor Inc.
MT9045
19
1kΩ
R
10kΩ
P
R
+3.3V
10nF
C
Data Sheet