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PRODUCT SPECIFICATION
RC2211A
3
Loop Phase Detector Output
(Pin 11)
This terminal provides a high impedance output for the loop
phase detector. The PLL loop filter is formed by R1 and C1
connected to pin 11 (see Figure 1). With no input signal, or
with no phase error within the PLL, the DC level at pin 11 is
very nearly equal to V
R
. The peak voltage swing available at
the phase detector output is equal to
±
V
R
.
VCO Control Input
(Pin 12)
VCO free running frequency is determined by external
timing resistor, R0, connected from this terminal to ground.
The VCO free running frequency, F
0
is given by:
where C
0
is the timing capacitor across pins 13 and 14. For
optimum temperature stability R
0
must be in the range of
10 k
W
to 100 k
W
(see Typical Performance Characteristics).
This terminal is a low impedance point, and is internally
biased at a DC level equal to V
R
. The maximum timing cur-
rent drawn from pin 12 must be limited to
£
3 mA for proper
operation of the circuit.
VCO Timing Capacitor
(Pins 13 and 14)
VCO frequency is inversely proportional to the external tim-
ing capacitor, C
0
, connected across these terminals. C
0
must
be non-polarized, and in the range of 200 pF to 10
m
F.
VCO Frequency Adjustment
VCO can be fine tuned by connecting a potentiometer, Rx, in
series with R
0
at pin 12 (see Figure 2).
VCO Free-Running Frequency,
F
0
The RC2211A does not have a separate VCO output termi-
nal. Instead, the VCO outputs are internally connected to the
phase detector sections of the circuit. However, for set-up or
adjustment purposes, the VCO freerunning frequency can be
measured at pin 3 (with C
D
disconnected) with no input and
with pin 2 shorted to pin 10.
Design Equations
See Figure 1 for Definitions of Components.
1.
VCO Center Frequency, F
0
:
F
0
Hz
(
)
R
0
C
0
----1
=
F
0
Hz
(
)
R
0
C
0
-----1
=
2.
Internal Reference Voltage, V
R
(measured at pin 10)
3.
Loop Lowpass Filter Time Constant,
t
t
= R
1
C
1
4.
Loop Dampening,
z
:
5.
Loop Tracking Bandwidth,
±D
F/F
0
:
6.
FSK Data Filter Time Constant,
t
F
:
t
F
= R
F
C
F
7.
Loop Phase Detector Conversion Gain, K
f
(K
f
is the
differential DC voltage across pins 10 and 11, per unit
of phase error at phase-detector input):
8.
VCO Conversion Gain, K
0
is the amount of change in
VCO frequency per unit of DC voltage change at pin 11:
9.
Total Loop Gain, K
T
:
K
T
(in radians per second per volt)= 2
p
K
f
K0
=
10. Peak Phase Detector Current, I
A
:
V
R
+V
S
2
----------
è
-650 mV
=
z
C
0
C
1
------
è
÷
è
=
65-2211-03
Tracking
Bandwidth
D
f
D
f
F
LL
F
1
F
0
F
2
F
LH
D
f/F
O
= R0/R1
k
f
in volts per radian
(
)
2
–
(
-----------------------
)
V
(
p
)
=
K0 in Hertz per volt
)
C
0
R
1
V
R
------–
=
C
0
R
1
-----4
I
A
mA
(
)
V
R
25
-------
=