XR2212 Exar Corporation, XR2212 Datasheet - Page 9

• Manufacturer Part Number: XR2212
• Description: Precision Phase-Locked Loop
• Manufacturer: Exar Corporation

current 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 timing capacitor,
C
must be nonpolar, and in the range of 200pF to 10 F.
VCO Quadrature Output (Pin 15): The low-level (
0.6Vpp) output at this pin is at quadrature phase (i.e. 90
phase-offset) with the other VCO outputs at Pins 3 and 5.
The DC level at Pin 15 is approximately 300mV above
V
multiplier as a “lock detect” circuit. In order not to degrade
oscillator performance, the output at Pin 15 must be
buffered with an external high impedance low
capacitance amplifier. When not in use, Pin 15 should be
left open-circuited.
Phase Detector Input (Pin 16): Voltage output of the
VCO (Pin 5) or the output of an external frequency divider
REF
0
, connected across these terminals (see Figure 6 ). C
Rev. 2.01
. The quadrature output can be used with an external
Figure 10. Phase Detector Output Voltage (Pin 10) as a Function of Input Signal Frequency
2V
V
R
0
R
Note
Output Voltage is Referenced to Internal Reference Voltage V
f
TL
Input Signal Frequency
0
9
f
Bandwidth
Tracking
is connected to this pin. The DC level of the sensing
threshold for the phase detector is referenced to V
the signal is capacitively coupled to Pin 16, then this pin
must be biased from Pin 11, through an external resistor,
R
16 must not exceed (V
PHASE-LOCKED LOOP PARAMETERS
Transfer Characteristics
Figure 10 shows the basic frequency to voltage
characteristics of XR-2212. With no input signal present,
filtered phase detector output voltage is approximately
equal to the internal reference voltage, V
The PLL can track an input signal over its tracking
bandwidth, shown in the figure. The frequencies f
f
range, f
TH
f
B
O
(R
represent the lower and the upper edge of the tracking
B
f
0
represents the VCO center frequency.
10k ). The peak voltage swing applied to Pin
f
TH
REF
at Pin 11
CC
- 1.5) volts.
Frequency
XR-2212
REF
at Pin 11.
TL
REF
and
. If