FXLC95000CL datasheet(13/38 Pages) FREESCALE

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4.3.1 Power supply considerations

• An internal circuit powered by VDDA provides the FXLC95000CL with a power-

on-reset signal. For this signal to be properly recognized, it is important that VDD

is powered up before or simultaneously with VDDA.

• The voltage potential difference between VDD and VDDA must not exceed ±0.1 V.

The simplest way to accomplish this is to power both pins from the same voltage

source.

• When using the same voltage source, some digital noise might reach the analog

section. To prevent this, connect a small inductor or ferrite bead in serial with

both the VDDA and VSSA traces. Additionally, two ceramic capacitors (of

approximately 1 µF, and 100 nF, respectively) can be used to efficiently bypass

the power and ground of both digital and analog supply rails.

• VDDIO must rise up before or simultaneously with VDDA/VDD.

4.3.2 General connections and layout recommendations

• Provide a low-impedance path from the board power supply to each power pin

(VDD, VDDA, and VDDIO) on the device and from the board ground to each

ground pin (VSS, VSSA, and VSSIO).

• The minimum bypass requirement is to place 0.01 – 0.1

μF capacitors positioned

as close as possible to the package supply pins. The recommended bypass

configuration is to place one bypass capacitor on each of the VDD/VSS pairs,

including VDDA/ VSSA. Ceramic and tantalum capacitors tend to provide better

tolerances.

• Ensure that capacitor leads, associated printed circuit traces, and vias that connect

to the chip VDD and VSS (GND) pins are as short as possible.

• Bypass the power and ground. It is suggested that a high-frequency bypass

capacitor be placed close to and on each power pin. Bulk capacitance also is

suggested, with it evenly distributed around the power and ground planes of the

board.

• Take special care to minimize noise levels on the VDDA and VSSA pins. An

isolation circuit consisting of a Ferrite Bead and capacitors is suggested, to ensure

that the voltage supplying the analog input is noise free.

• Use separate power planes for VDD and VDDA and separate ground planes for

VSS and VSSA. Connect the separate analog and digital power and ground planes

as close as possible to power supply outputs. If both analog circuit and digital

circuit are powered by the same power supply, it is advisable to connect a small

inductor or ferrite bead in serial with both VDDA and VSSA traces.

General Description

Xtrinsic FXLC95000CL Intelligent, Motion-Sensing Platform, Rev1.2, 8/2013.

Freescale Semiconductor, Inc.

FXLC95000CL датащи(PDF) 13 Page - Freescale Semiconductor, Inc