ICS843002I-41 Datasheet, PDF (12/21 Pages) Integrated Circuit Systems – 700MHz, FEMTOCLOCKS-TM VCXO BASED SONET/SDH JITTER ATTENUATOR

Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS843002I-41
700MHZ, FEMTOCLOCKS™ VCXO BASED
SONET/SDH JITTER ATTENUATOR
NOTES ON SETTING CHARGE PUMP CURRENT
The recommended range for the charge pump current is 50μA
to 300μA. Below 50μA, loop filter charge leakage, due to PCB or
capacitor leakage, can become a problem.This loop filter leakage
can cause locking problems, output clock cycle slips, or low
frequency phase noise.
As can be seen in the loop bandwidth and damping factor
equations or by using the filter response software available from
ICS, increasing charge pump current (I_CP) increases both
bandwidth and damping factor.
CHARGE PUMP CURRENT, EXAMPLE SETTINGS
R_SET
17.6k
8.8k
4.4k
2.2k
Charge Pump Current (I_CP)
62.5µA
125µA
250µA
500µA
1E-3
100E-6
10E-6
1k
10k
R_SET, Ω
100k
FIGURE 1.
CHARGE
PUMP
CURRENT
VS.
VALUE
OF
R
SET
(EXTERNAL
RESISTOR)
GRAPH
843002AKI-41
www.icst.com/products/hiperclocks.html
12
REV. A JUNE 1, 2005