AN4092 datasheet(22/38 Pages) STMICROELECTRONICS

Part #	AN4092

Description	Low to mid range engine management

PDF	38 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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22 / 38 page

FMPLL and crystal oscillator

AN4092

22/38

Doc ID 023080 Rev 2

2.5

Layout recommendations

●

Keep the area of the oscillator circuit as compact as possible, keep tracks very short;

●

Avoid any track crossing the oscillator area, also considering inner layers between the

components and the ground plane;

●

Keep the routing on one layer;

●

Create an island for the oscillator ground on the top layer;

●

Open all the inner layers in correspondence of the oscillator to reduce capacitance;

●

Surround the oscillator area on component side with a GND guard, do not fill the area

with ground. To be effective, the guard trace must be grounded by vias every a short

lenght (< wavelenght / 20, with reference at the higher frequency present);

●

Use robust SMT pads for components in crystal oscillator, short track lengths for all

signals.

Figure 9.

PCB layout example for SPC563Mxx / SPC564Axx

AN4092 Datasheet(PDF) 22 Page - STMicroelectronics