xr215a Exar Corporation, xr215a Datasheet - Page 18

• Manufacturer Part Number: xr215a
• Description: Monolithic Phase-locked Loop
• Manufacturer: Exar Corporation

Low-Pass Filter
The low-pass filter section is formed by connecting an
external capacitor or RC network across terminals 2 and
3. The low-pass filter components can be connected
either between pins 2 and 3 or, from each pin to ground.
Typical filter configurations and corresponding filter
Note:
The natural frequency
K
Then the damping factor can be calculated using:
d
R
XR-215A
, and the low pass filter time constants
1
= 6k internal resistor.
Rev. 1.01
n
n
2
n
can be calculated from the VCO conversion gain K
K
2
F(s) =
1
F(s) =
0
Lag Filter
2
1
· K
C
1
= R
= 2R
1
2
C
1
2
d
S
1
S
1
C
1
1
1
K
1
1
C
3
0
1
C
1
· K
3
1
d
1
and
2
as follows:
Figure 15.
18
transfer functions are shown in Figure 15 where R
is the internal impedance at pins 2 and 3. It should be
noted that the rejection of the low pass filter decreases
above 2MHz when the capacitor is tied from pin 2 to 3.
F(s) =
2
1
2
F(s) =
Lag Lead Filter
= R
= R
2
C
R
1
2
1
2
R
0
= 2R
= R
2
1 + S(
1
, the phase comparator conversion gain
2
C
C
1 + S(
1
1 + S
2
1
C
1
1 + S
C
1
1
1
C
+
3
C
R
2
1
1
+
1
2
2
2
)
2
)
3
1
(6k )