RC2211
PRODUCT SPECIFICATION
Loop Phase Detector Output (Pin 11)
This terminal provides a high impedance output for the loop
phase detector. The PLL loop Þlter 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 VR. The peak voltage swing available at
the phase detector output is equal to ±VR.
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, F0 is given by:
F0 (Hz)
=
------1-------
R0C0
where C0 is the timing capacitor across pins 13 and 14. For
optimum temperature stability R0 must be in the range of
10 kW to 100 kW (see Typical Performance Characteristics).
This terminal is a low impedance point, and is internally
biased at a DC level equal to VR. 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, C0, connected across these terminals. C0 must
be non-polarized, and in the range of 200 pF to 10 mF.
VCO Frequency Adjustment
VCO can be Þne tuned by connecting a potentiometer, Rx, in
series with R0 at pin 12 (see Figure 2).
VCO Free-Running Frequency, F0
The RC2211 does not have a separate VCO output terminal.
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 CD disconnected) with no input and
with pin 2 shorted to pin 10.
Design Equations
See Figure 1 for DeÞnitions of Components.
1. VCO Center Frequency, F0:
F0 (Hz)
=
------1-------
R0C0
2. Internal Reference Voltage, VR (measured at pin 10)
VR
=
æ
è
-+---V2-----S-øö
-650
mV
3. Loop Lowpass Filter Time Constant, t
t = R1C1
4. Loop Dampening, z:
æ
z=ç
è
C-----0-÷ö
C1ø
æ
è
14--
ö
ø
5. Loop Tracking Bandwidth, ±DF/F0:
Df/FO = R0/R1
Tracking
Bandwidth
Df Df
FLL F1
F0 F2 FLH
65-2211-03
6. FSK Data Filter Time Constant, tF:
tF = RFCF
7. Loop Phase Detector Conversion Gain, Kf (Kf is the
differential DC voltage across pins 10 and 11, per unit
of phase error at phase-detector input):
kf (in volts per radian) = -(---Ð---2----)--p--(--V-----R---)--
8. VCO Conversion Gain, K0 is the amount of change in
VCO frequency per unit of DC voltage change at pin 11:
K0 (in Hertz per volt)
=
--------Ð---1----------
C0R1VR
9. Total Loop Gain, KT:
KT (in radians per second per volt)= 2 pKfK0
= ------4-------
C0R1
10. Peak Phase Detector Current, IA:
IA (mA)
=
-V----R--
25
3