ICS843034 datasheet(22/31 Pages) RENESAS

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December 2, 2015

843034 DATA SHEET

Application Schematic Example

Figure 7 (next page) shows an example of 843034 application

schematic. In this example, the device is operated at VCC = VCCO_A

= VCCO_B = VCCO_REF = 3.3V. An 18pF parallel resonant 25MHz

crystal is used. The load capacitance C1 = 18pF and C2 = 22pF are

recommended for frequency accuracy. Depending on the parasitics

of the printed circuit board layout, these values might required slight

adjustment to optimize the frequency accuracy. Crystals with other

load capacitance specifications can be used. This will require

adjusting C1 and C2. For this device, the crystal load capacitors are

required for proper operation.

As with any high speed analog circuitry, the power supply pins are

vulnerable to noise. To achieve optimum jitter performance, power

supply isolation is required. The 843034 provides separate power

supplies to isolate to isolate any high switching noise from coupling

into the internal PLL.

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

0.1uF 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.

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 with high amplitude

interference is known, such as switching power supplies

frequencies, it is recommended that component values be adjusted

and if required, additional filtering be added. Additionally general

design practice for power plane voltage stability suggests adding

bulk capacitances in the general area of all devices.

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 the logic control inputs are properly

set.

ICS843034 датащи(PDF) 22 Page - Renesas Technology Corp