MC145152-2 Freescale Semiconductor, Inc, MC145152-2 Datasheet - Page 19
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MC145152-2
Manufacturer Part Number
MC145152-2
Description
Parallel-input Pll Frequency Synthesizer
Manufacturer
Freescale Semiconductor, Inc
Datasheet
1.MC145152-2.pdf
(24 pages)
4.2
The following options may be considered to provide a reference frequency to Freescale's CMOS frequency
synthesizers.
4.2.1
Commercially available temperature-compensated crystal oscillators (TCXOs) or crystal-controlled data
clock oscillators provide very stable reference frequencies. An oscillator capable of sinking and sourcing
50 µA at CMOS logic levels may be direct or dc coupled to OSC
capability is obtained utilizing a direct-coupled square wave having a rail-to-rail (V
swing. If the oscillator does not have CMOS logic levels on the outputs, capacitive or ac coupling to OSC
may be used. OSC
4.2.2
The user may design an off-chip crystal oscillator using ICs specifically developed for crystal oscillator
applications, or using discrete transistors. The reference signal from the oscillator is ac coupled to OSC
For large amplitude signals (standard CMOS logic levels), dc coupling is used. OSC
output, should be left floating. In general, the highest frequency capability is obtained with a
direct-coupled square wave having rail-to-rail voltage swing.
4.2.3
The on-chip amplifier (a digital inverter) along with an appropriate crystal may be used to provide a
reference source frequency. A fundamental mode crystal, parallel resonant at the desired operating
frequency, should be connected as shown in
Freescale Semiconductor
Crystal Oscillator Considerations
Use of a Hybrid Crystal Oscillator
Design an Off-Chip Reference
Use of the On-Chip Oscillator Circuitry
out
, an unbuffered output, should be left floating.
MC145151-2 and MC145152-2 Technical Data, Rev. 5
Figure 13. Pierce Crystal Oscillator Circuit
* May be deleted in certain cases. See text.
OSC
C1
in
Figure
R
13.
C2
f
R1*
FREQUENCY
SYNTHESIZER
OSC
out
in
. In general, the highest frequency
DD
out
Design Considerations
, an unbuffered
to V
SS
) voltage
in
19
in
.