XR-2212 Datasheet, PDF (14/20 Pages) Exar Corporation – Precision Phase-Locked Loop

XR-2212
INPUT SENSITIVITY
The input to the XR-2212 may sometimes be too sensitive
to noise conditions on the input line. Figure 13 illustrates
a method of de-sensitizing the XR-2212 from such noisy
line conditions by the use of a resistor, Rx, connected from
pin 2 to ground. The value of Rx is chosen by the equation
and the desired minimum signal threshold level.
V_IN minimum (peak) input voltage must exceed this value
to be detected (equivalent to adjusting V threshold).
V_IN minimum (peak) + V_a–V_b +
DV " 2.8V
offset
+
VREF
+
20, 000
(20, 000 )
RX)
or
ǒ Ǔ _{RX + 20, 000}
VREF
DV
*
1
Vcc
Input
ÎÎ Va
2
Rx
20K
ÎÎÎÎ _{VREF 11}
To Phase
Detector
Vb
20K
Figure 13. Desensitizing Input Stage
Rev. 2.01
14