8V43042 Datasheet
Schematic Example
Figure 3 shows an example of 8V43042 application schematic. In this
example, the device is operated at VCC = VCCA = VCCO = 3.3V. The
schematic example focuses on functional connections and is not
configuration specific. Refer to the pin description and functional
tables in the datasheet to ensure that the logic control inputs are
properly set.
In order to achieve the best possible filtering, it is recommended that
the placement of the filter components be on the device side of the
PCB as close to the power pins as possible. If space is limited, the
0.1µF capacitor in each power pin filter should be placed on the
device side. The other components can be on the opposite side of the
PCB.
A 12pF parallel resonant 25MHz crystal is used. For this device, the
crystal load capacitors are required for proper operation. The load
capacitance, C1 = C2 = 10pF, are recommended for frequency
accuracy. Depending on the variation of the parasitic stray capacity
of the printed circuit board traces between the crystal and the
XXTAL_IN and XXTAL_OUT pins, the values of C1 and C2 might
require a slight adjustment to optimize the frequency accuracy.
Crystals with other load capacitance specifications can be used, but
this will require adjusting C1 and C2. When designing the circuit
board, return the capacitors to ground though a single point contact
close to the package. Two Fox crystal options are shown in the
schematic for design flexibility.
Power supply filter recommendations are a general guideline to be
used for reducing external noise from coupling into the devices. The
filter performance is designed for a wide range of noise frequencies.
This low-pass filter starts to attenuate noise at approximately 10kHz.
If a specific frequency noise component is known, such as switching
power supplies frequencies, it is recommended that component
values be adjusted and if required, additional filtering be added.
Additionally, good general design practices for power plane voltage
stability suggests adding bulk capacitance in the local area of all
devices.
As with any high speed analog circuitry, the power supply pins are
vulnerable to random noise. To achieve optimum jitter performance,
power supply isolation is required. The 8V43042 provides separate
power supplies to isolate any high switching noise from coupling into
the internal PLL.
©2016 Integrated Device Technology, Inc.
11
Revison C, November 3, 2016
