MC12179 View Datasheet(PDF) - Motorola => Freescale
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MC12179 Datasheet PDF : 11 Pages
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Freescale SMeCm1i2c1o79nductor, Inc.
Figure 1. MC12179 Expanded Block Diagram
+5.0 V
2 VCC
C1
1 OSCin
8 OSCout
C2
NOTE: External 50 kΩ resistor
across Pins 1 and 8 is necessary in
either crystal or driven mode.
VCO
4 Fin
1000 pF
Crystal
Oscillator
Prescaler
÷256
fr
Phase/Frequency
Detector
fv
Charge
Pump
GND
GNDP
3
5
+5.0 V
VP 7
6
PDout
To Loop Filter
PHASE CHARACTERISTICS
The phase comparator in the MC12179 is a high speed
digital phase/frequency detector circuit. The circuit
determines the “lead” or “lag” phase relationship and time
difference between the leading edges of the VCO (fv) signal
and the reference (fr) input. The detector can cover a range of
±2π radian of fv/fr phase difference. The operation of the
charge pump output is shown in Figure 2.
fr lags fv in phase OR fv>fr in frequency
When the phase of fr lags that of fv or the frequency of fv is
greater than fr, the Do output will sink current. The pulse
width will be determined by the time difference between the
two rising edges.
fr leads fv in phase OR fv<fr in frequency
When the phase of fr leads that of fv or the frequency of fv
is less than fr, the Do output will source current. The pulse
width will be determined by the time difference between the
two rising edges.
fr = fv in phase and frequency
When the phase and frequency of fr and fv are equal, the
charge pump will be in a quiet state, except for current spikes
when signals are in phase. This situation indicates that the
loop is in lock and the phase comparator will maintain the
loop in its locked state.
fr
(OSCin)
fv
(Fin ÷256)
PDout
Figure 2. Phase/Frequency Detector and Charge Pump Waveforms
H
L
H
L
Sourcing Current Pulse
Z
Sinking Current Pulse
H = High voltage level; L = Low voltage level; Z = High impedance
NOTES: Phase difference detection range: ∼ –2π to 2π
[ ) + ) + Kp–Charge Pump Gain
|Isource| |Isink|
4p
|2.2| |–2.2|
4p
1.1 mA
pradian
MOTOROLA RF/IF DEVICE DATA For More Information On This Product,
3
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