AN4630 datasheet(12/33 Pages) STMICROELECTRONICS

Part #	AN4630

Description	PCB design guidelines for the BlueNRG and BlueNRG-MS devices

PDF	33 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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12 / 33 page

Components dimensioning

AN4630

2.3

External quarts

The BlueNRG includes a high frequency and a low-frequency integrated oscillators that

required two external crystals.

The BlueNRG includes a fully integrated, low power 16/32 MHz Xtal oscillator with an

embedded amplitude regulation loop. In order to achieve low power operation and good

frequency stability of the Xtal oscillator, certain considerations with respect to the quartz

load capacitance C0 need to be taken into account. Figure 8: "Diagram of the BlueNRG

amplitude regulated oscillator" shows a simplified block diagram of the amplitude regulated

oscillator used on the BlueNRG.

Figure 8: Diagram of the BlueNRG amplitude regulated oscillator

Low power consumption and fast startup time are achieved by choosing a quartz crystal

with a small load capacitance C0. A reasonable choice for capacitor C0 is 15 pF. To

achieve good frequency stability, the following equation needs to be satisfied:

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AN4630 Datasheet(PDF) 12 Page - STMicroelectronics