MK3732-22
BLU-RAY DISC VCXO VCXO AND SYNTHESIZER
IDT™ / ICS™
BLU-RAY DISC VCXO 3
MK3732-22 REV D 020906
External Components
Decoupling Capacitor
As with any high-performance mixed-signal IC, the
MK3732-22 must be isolated from system power supply
noise to perform optimally.
A decoupling capacitor of 0.01µF must be connected
between each VDD and the PCB ground plane.
Series Termination Resistor
Clock output traces over one inch should use series
termination. To series terminate a 50Ω trace (a commonly
used trace impedance), place a 33Ω resistor in series with
the clock line, as close to the clock output pin as possible.
The nominal impedance of the clock output is 20Ω.
Quartz Crystal
The MK3732-22 VCXO function consists of the external
crystal and the integrated VCXO oscillator circuit. To assure
the best system performance (frequency pull range) and
reliability, the layout guidelines discussed in the following
section must be followed.
The frequency of oscillation of a quartz crystal is determined
by its “cut” and by the load capacitors connected to it. The
MK3732-22 incorporates on-chip variable load capacitors
that “pull” (change) the frequency of the crystal. The crystal
specified for use with the MK3732-22 is designed to have
zero frequency error when the total of on-chip + stray
capacitance is 12 pF.
The external crystal must be connected as close to the chip
as possible and should be on the same side of the PCB as
the MK3732-22. There should be no vias between the
crystal pins and the X1 and X2 device pins. There should be
no signal traces underneath or close to the crystal.
Crystal Tuning Load Capacitors
The crystal traces should include pads for small fixed
capacitors, one between X1 and ground, and another
between X2 and ground. Stuffing of these capacitors on the
PCB is optional. The need for these capacitors is
determined at system prototype evaluation, and is
influenced by the particular crystal used (manufacture and
frequency) and by PCB layout. The typical required
capacitor value is 1 to 4 pF.
To determine the need for and value of the crystal
adjustment capacitors, you will need a PC board of your final
layout, a frequency counter capable of about 1 ppm
resolution and accuracy, two power supplies, and some
samples of the crystals which you plan to use in production,
along with measured initial accuracy for each crystal at the
specified crystal load capacitance, CL.
To determine the value of the crystal capacitors:
1. Connect VDD of the MK3732-22 to 3.3 V. Connect pin 4
of the MK3732-22 to the second power supply. Adjust the
voltage on pin 4 to 0V. Measure and record the frequency of
the 13.5 M output.
2. Adjust the voltage on pin 4 to 3.3 V. Measure and record
the frequency of the same output.
To calculate the centering error:
18 OE Input Output enable. Tri-states all output when low. Internal pull-up
19 VDD Power Connect to +3.3 V.
20 X2 Output Crystal connection. Connect to 13.5 MHz fundamental mode pullable
crystal.
Pin
Number
Pin
Name
Pin
Type
Pin Description
Error 10
6
x
f
3.3V
f
tetarg
–()f
0V
f
tetarg
–()+
f
tetarg
------------------------------------------------------------------------------
error
xtal
–=
