FXLC95000CL Datasheet, PDF (13/38 Pages) Freescale Semiconductor, Inc – Xtrinsic FXLC95000CL Intelligent, Motion-Sensing Platform

General Description
4.3.1 Power supply considerations
• An internal circuit powered by V_DDA provides the FXLC95000CL with a power-
on-reset signal. For this signal to be properly recognized, it is important that V_DD
is powered up before or simultaneously with V_DDA.
• The voltage potential difference between V_DD and V_DDA 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 V_DDA and V_SSA 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.
• V_DDIO must rise up before or simultaneously with V_DDA/V_DD.
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.
Xtrinsic FXLC95000CL Intelligent, Motion-Sensing Platform, Rev1.2, 8/2013.
13
Freescale Semiconductor, Inc.