Application Guide - XMC4000 - PCB Design Guidelines

XMC4000
Microcontroller Series
for Industrial Applications
PC B Desi gn
 Guidelines
Applic atio n Guid e
V1.0 2013-11
Microcontrollers
Edition 2013-11
Published by
Infineon Technologies AG
81726 Munich, Germany
© 2013 Infineon Technologies AG
All Rights Reserved.
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PCB Design
XMC4000 Family
Revision History
Revision History
Page or Item
Subjects (major changes since previous revision)
V1.0, 2013-11
Trademarks of Infineon Technologies AG
AURIX™, C166™, CanPAK™, CIPOS™, CIPURSE™, EconoPACK™, CoolMOS™, CoolSET™,
CORECONTROL™, CROSSAVE™, DAVE™, EasyPIM™, EconoBRIDGE™, EconoDUAL™,
EconoPIM™, EiceDRIVER™, eupec™, FCOS™, HITFET™, HybridPACK™, I²RF™, ISOFACE™,
IsoPACK™, MIPAQ™, ModSTACK™, my-d™, NovalithIC™, OptiMOS™, ORIGA™, PRIMARION™,
PrimePACK™, PrimeSTACK™, PRO-SIL™, PROFET™, RASIC™, ReverSave™, SatRIC™,
SIEGET™, SINDRION™, SIPMOS™, SmartLEWIS™, SOLID FLASH™, TEMPFET™, thinQ!™,
TRENCHSTOP™, TriCore™.
Other Trademarks
Advance Design System™ (ADS) of Agilent Technologies, AMBA™, ARM™, MULTI-ICE™, KEIL™,
PRIMECELL™, REALVIEW™, THUMB™, µVision™ of ARM Limited, UK. AUTOSAR™ is licensed by
AUTOSAR development partnership. Bluetooth™ of Bluetooth SIG Inc. CAT-iq™ of DECT Forum.
COLOSSUS™, FirstGPS™ of Trimble Navigation Ltd. EMV™ of EMVCo, LLC (Visa Holdings Inc.).
EPCOS™ of Epcos AG. FLEXGO™ of Microsoft Corporation. FlexRay™ is licensed by FlexRay
Consortium. HYPERTERMINAL™ of Hilgraeve Incorporated. IEC™ of Commission Electrotechnique
Internationale. IrDA™ of Infrared Data Association Corporation. ISO™ of INTERNATIONAL
ORGANIZATION FOR STANDARDIZATION. MATLAB™ of MathWorks, Inc. MAXIM™ of Maxim
Integrated Products, Inc. MICROTEC™, NUCLEUS™ of Mentor Graphics Corporation. Mifare™ of
NXP. MIPI™ of MIPI Alliance, Inc. MIPS™ of MIPS Technologies, Inc., USA. muRata™ of MURATA
MANUFACTURING CO., MICROWAVE OFFICE™ (MWO) of Applied Wave Research Inc.,
OmniVision™ of OmniVision Technologies, Inc. Openwave™ Openwave Systems Inc. RED HAT™
Red Hat, Inc. RFMD™ RF Micro Devices, Inc. SIRIUS™ of Sirius Satellite Radio Inc. SOLARIS™ of
Sun Microsystems, Inc. SPANSION™ of Spansion LLC Ltd. Symbian™ of Symbian Software Limited.
TAIYO YUDEN™ of Taiyo Yuden Co. TEAKLITE™ of CEVA, Inc. TEKTRONIX™ of Tektronix Inc.
TOKO™ of TOKO KABUSHIKI KAISHA TA. UNIX™ of X/Open Company Limited. VERILOG™,
PALLADIUM™ of Cadence Design Systems, Inc. VLYNQ™ of Texas Instruments Incorporated.
VXWORKS™, WIND RIVER™ of WIND RIVER SYSTEMS, INC. ZETEX™ of Diodes Zetex Limited.
Last Trademarks Update 2011-02-24
PCB Design
XMC4000 Family
Table of Contents
Table of Contents
Revision History .................................................................................................................................................... 3
Table of Contents .................................................................................................................................................. 4
Guidelines............................................................................................................................................................... 5
Application Guide
4
V1.0, 2013-11
PCB Design
XMC4000 Family
Introduction
Guidelines
Application Guide
5
V1.0, 2013-11
PCB Design
XMC4000 Family
Introduction
1
Introduction
The XMC4000 family is an ARM® Cortex™-M4 based 32-bit microcontroller family available in VQFN48, LQFP-64/100/144 and LGBGA-144 pin packages. This application guide helps to design a PCB
with respect to:
 electromagnetic compatibility
 power supply system
 performance of analog peripherals
 thermal management
In addition to the Infineon PCB Design Guidelines for Microcontrollers (AP24026), which gives
general design rules for PCB design, some product-specific recommendations and guidelines for the
XMC4000 family are provided in this document.
Note: This application note contains design recommendations from Infineon Technologies point of
view. Effectiveness and performance of the final application implementation must be validated
by the customer, based on dedicated implementation choices. Other design implementations
can also be applied.
2
General Information
The XM4000 family has four different power domains:
 Pad Domain (VDDP, 3.3V, supplied externally)
 Analog Domain (VDDA, 3.3V, supplied externally)
 Core Domain (VDDC, 1.3V, generated internally)
 Hibernate Domain (VBAT, 2.0-3.6V, supplied externally)
The Pad Domain VDDP and the Analog Domain VDDA with a nominal voltage of 3.3V must be
supplied and decoupled externally.
The Core Domain supply with a nominal voltage of 1.3V is generated out of the Pad Domain supply
by an on-chip EVR (Embedded Voltage Regulator). The VDDC pins are the output of the EVR and
must be stabilized and decoupled with external decoupling capacitors on the PCB.
The supply pin VBAT of the Hibernate Domain can be connected to a battery coin cell or large
capacitor. Even if the hibernate features are not used, the VBAT pin must always be connected to a
power supply, when VDDP is supplied.
Note: The VBAT pin must always be supplied, when VDDP is supplied. Tie the VBAT pin directly to
VDDP, if no other circuitry for VBAT is destined.
3
PCB Design Recommendations
3.1
Clock Output
To minimize the EMI radiation on the PCB some measures have to be considered if the external clock
output feature via the clock pin EXTCLK (P0.8 or P1.15) is used:
 Reduced the driver strength of the pin if possible by choosing a weak pad drive mode (register
P0_PDR0 or P1_PDR15 respectively)
 Route this signal with adjacent ground reference and avoid signal and reference layer changes
 Route it as short as possible
 Routing ground on each side can help to reduce coupling to the other signals (crosstalk)
Application Guide
6
V1.0, 2013-11
PCB Design
XMC4000 Family
PCB Design Recommendations
3.2
Unused Pins
For unused pins the measures listed in Table 1 should be considered.
Table 1
Measures for unused pins
Unused Function / Unused Pin
Power Supply Pins (VDDP, VDDA,
VDDC, VBAT, VSS including exposed
pad, VSSA, VSSO, VAGND)
Reference Voltage of the ADC
(VAREF)
Port Pins (P0-P15)
Recommended measure if pin is not used
 These pins must always be connected to an appropriate
power supply or power circuitry!



External oscillator pins (XTAL1, XTAL2, 
RTC_XTAL1, RTC_XTAL2)


USB Pins (USB_DP, USB_DM, VBUS) 

Serial Wire Debug Pins (TMS, TCK)

Reset Pin (PORST#)
Hibernate Pins (HIB_IO_0, HIB_IO_1)



Application Guide
Leave VAREF open (ADC cannot be used, digital input
function of P14 and P15 is still working)
Pins should be configured as “direct input” with an “internal
pull-up [or pull-down] device active” via the register Pn_IOCR
Pins should be left open and should not be connected to any
other net (layout isolated PCB pad, for soldering only)
Leave XTAL1 / RTC_XTAL1 open if the corresponding
oscillator is in dower-down
Connect a pull-down resistor to XTAL1 / RTC_XTAL1 or tie
directly to GND (VSS) if the corresponding oscillator is not in
dower-down
Leave XTAL2 / RTC_XTAL2 open
Leave USB_DP, USB_DM and VBUS open
Leave TMS and TCK open
Leave PORST# open
Leave HIB_IO_0 open (after reset this pin is driving a low
level)
Leave HIB_IO_1 open if the Hibernate domain is not enabled
(SCU_PWRSTAT.HIBEN == 0)
Leave HIB_IO_1 open and configure as “Direct input, Input
pull-down device connected” (HDCR.HIBIO1SEL = 0001B) if
the Hibernate domain is enabled (SCU_PWRSTAT.HIBEN
== 1)
7
V1.0, 2013-11
PCB Design
XMC4000 Family
PCB Design Recommendations
3.3
Main Oscillator (XTAL1 / XTAL2)
To reduce the radiation / coupling from the main oscillator circuit, a separated ground island on the
GND layer should be designed (see Figure 1). This ground island can be connected at one point to
the GND layer. Ideally this point is close to the VSSO pin (not available in all packages). This helps to
keep the noise generated by the oscillator circuit locally on this separated island. The ground
connections of the load capacitors and VSSO should also be connected to this island. Traces for load
capacitors and Crystal should be as short as possible.
GND Plane
Via to GND
Plane
VSSO
μC
XTAL2
C
R
Crystal
XTAL1
C
VSS
Via to GND
Plane
Figure 1
3.4




Separated GND Island on TOP layer
(carved out from global GND layer)
Separated Ground Island for the Main Ocsillator
Power Supply Domains
All VDDC pins must be connected to one net on the PCB, even if they are internally connected by
each other, because the impedance of the external connection is much lower than the internal
connection.
A low inductance value for the connection of decoupling capacitors to the supply pins is required.
Therefor place the decoupling capacitors close to the corresponding power supply pin group.
All supply domains should be decoupled separately with Low ESR and Low ESL capacitors
(ceramic multilayer capacitors preferably)
Use the capacitors values for decoupling/stabilization as shown in Table 2.
Table 2
Decoupling / Stabilization Capacitor Values
Power Supply Domain
Number and Sizes of Decoupling / Stabilization capacitors
Pad Domain VDDP/VSS
100 nF to each VDDP pin, 20 μF or higher to one pin
Analog Domain VDDA/VSSA
100 nF to VDDA pin
Core Domain VDDC/VSS
XMC4500: 100 nF to each VDDC pin, 10 μF ±10% X7R to one pin
XMC4400/XMC4200: 100 nF to each VDDC pin, 4.7 μF ±10% X7R to one pin
Hibernate Domain VBAT
Any value, depends on hibernate time



All power supply pins (supplied from a voltage regulator) should be connected first to the
dedicated decoupling capacitor and then from the capacitors over vias to the power supply planes
All VSS pins should be connected to the GND layer
The power distribution from the regulator to each power plane should be made over filters (EMI
filter using ferrite beads).
Application Guide
8
V1.0, 2013-11
PCB Design
XMC4000 Family
PCB Design Recommendations

Inductance/ferrite beads in the range L ~5-10μH should be inserted in the supply paths at the
regulator output.
 Avoid cutting the GND plane by via groups. A solid GND plane must be designed.
 Depending on power dissipation (refer to the Data Sheet) the exposed pad should be connected to
sufficient GND area on all layers.
A power-plane/grounding concept example for the XMC4000 microcontrollers can be found in Figure
2.
Figure 2
2-layer PCB Layout Example for Decoupling of XMC4000 (single sided assembly)
VDDP on TOP Layer
VDDC on TOP Layer
VSS on TOP Layer
100
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VBAT on TOP Layer
VDDP
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51
VDDP
VBAT
VDDC
VSS
VSS/GND
VDDC
VDDP
VAREF on TOP Layer
VDDA on TOP Layer
Via to VSS/GND Layer
Bridge on Bottom Layer
VSS on BOTTOM Layer
BOTTOM
Layer
VAREF
Application Guide
VDDP
VDDA
VAREF
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TOP
Layer
VDDA
VSS /
GND
VDDP
9
V1.0, 2013-11
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