Application Guide - Common Mode Filter - Nexperia · GSM/3G/LTE WiFi Diplexer/Antenna ... ESD is...
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Transcript of Application Guide - Common Mode Filter - Nexperia · GSM/3G/LTE WiFi Diplexer/Antenna ... ESD is...
Common-mode filters with integrated ESD protectionfor portable devices
Application Guide - Common Mode Filter
2
Table of contents
1. Two challenges: ESD and EMI 6-9
3. Filtering and protecting MIPI lines (PCMFxDFN1) 11-15
2. Common-mode filters and the future of mobile 10
4. Filtering and protecting USB 2.0 (IP3319CX6) 16-18
5. A special situation: ESD protection for the SoC 19
Protecting portablesToday’s portable devices use very fast data lines to support displays, cameras, and other interfaces. Advanced processors, wireless features, and high-speed data lines help to maintain high levels of performance in these portable systems, but these features also present certain design challenges. They’re susceptible to EMI, can be vulnerable to ESD strikes, and can emit EMI. For these reasons, they require a certain amount of filtering and protection.
The block diagrams show how NXP’s PCMF family of common-mode filters with integrated ESD protection can improve performance and reduce risk in cell phones and other portable devices.
Display Applicationswith differential
data lines
Back SideCamera
Front SideCamera
ESD protection
Common Mode Filter with ESD protection
EMI interference
Risk of ESD strikes - directly or through gaps in the cabinet
Tactile keys
GSM/3G/LTEWiFi
Diplexer/Antenna
Processor
Generic smartphone / tablet computer
Introduction
4
The NXP advantageOur common-mode filters with integrated ESD protection are just one small part of what we can do for portable systems. As a recognized leader in portable and mobile applications, we offer a comprehensive portfolio of best-in-class solutions. We have strong partnerships with major handset, computer, and tablet makers, and consistently introduce new technologies that set the standard for performance, efficiency, and size. We are known for reliability, and back all our products with a cost-efficient supply chain and a company-wide commitment to the highest standards in quality. Simply put, our customers gain the confidence that comes from working with a world-class partner.
This guideThis Application guide summarizes key concepts for working with portable systems equipped with differential data lines and introduces how to use our common-mode filters with integrated ESD protection. To learn more, please visit www.nxp.com.
ESD protection for optional low-speed interfaces
HDMI interface
ESD protection
Common Mode Filter with ESD protection
EMI interference
Risk of ESD strikes - directly or through gaps in the cabinet
Tactile keys
USB interface
WiFi/Bluetoothantenna
Processor
Generic set-top box
5
1. Two challenges: ESD and EMI
Electrostatic discharge (ESD)ESD is the sudden release of static electricity. It can be caused by two electrically charged objects coming into contact, or coming close enough to allow air-discharge.
Opportunities for ESD strikes are just about everywhere. Wool or silk clothing, in combination with friction, can generate up to 10 kV of static electricity. Similar ESD conditions can be caused by something as simple as walking across a carpeted room or brushing against an upholstered seat when getting out of a car. Dry air, caused by cold weather or air conditioning, enhances this effect.
Portable devices are especially prone to ESD strikes because they go everywhere we go and are exposed to a very wide variety of environments. NXP’s common-mode filters with integrated ESD protection provide advanced countermeasures that prevent ESD from damaging portable devices.
ESD Strike
ESD can damage electronics and cause product returns
ESD sensitivity can violate regulation
Non-compliant product can be blocked from sale
6
1. Two challenges: ESD and EMI
Electromagnetic interference (EMI)The interference generated by electromagnetic fields can disrupt the operation of electronic devices. In cell phones, for example, EMI can lead to dropped calls and other malfunctions.
EMI can come from external sources, such as nearby electronics systems, which can produce EMI over a wide frequency range, but EMI can also come from within the system itself. High-speed data lines are a particular source of EMI. In a cell phone equipped with a high-speed MIPI line that supports a camera or display, the MIPI line can generate enough EMI to cause a dropped call. It’s important to understand and meet the guidelines for electromagnetic compatibility (EMC), since portable devices that violate these regulations may be blocked from sale.
NXP’s common-mode filters with integrated ESD protection work as filters that minimize the impact of EMI emission and reception, making it easier to design portable systems that meet EMC requirements.
EMI can impair functionality
EMI can violate regulations
Dropped phone calls can be caused by a MIPI line
emitting EMI
Affected products can be blocked from sale
7
1. Two challenges: ESD and EMI
Common-mode noiseToday’s portable systems replace single-ended signals with differential data lines that support high-speed interfaces. Differential data lines are typically more robust than single-ended signals, since they are less sensitive to common-mode noise, a type of EMI that runs along signal lines with the same amplitude and polarity.
When a signal from the transmitter is passed on to the receiver, the receiver detects the difference between the signals on the positive and negative lines. When the same amount of common-mode noise is added to both lines, the receiver does not detect it in an ideal system. The system isn’t influenced by common-mode noise and will not generate EMI.
The reality, however, is that common-mode noise is rarely in perfect balance on both lines. This is because common-mode noise can come from many sources, including the system chip. It can also come from the conversion of differential mode to common mode, which can be created by imbalances in signal symmetries and run-time differences, and it can be the result of the line pair not being symmetrical to the source of noise.
For this reason, portable systems benefit from common-mode filtering.
Conversion of differential mode to common mode
Line pair not symmetrical to source of noise
Imbalancedsignal symmetries
Run-timedifferences
8
1. Two challenges: ESD and EMI
How common-mode filters workCommon-mode filters have two magnetically-coupled coils.
When a differential signal passes through the filter, it generates a magnetic field in each coil. The magnetic fields compensate each other, resulting in an inductance close to zero. The high bandwidth of the filter lets the differential signals pass without attenuation.
When common-mode noise signals pass through the filter, the magnetic fields have the same direction. These fields add up and the resultant inductance is therefore as designed. This establishes a low pass, which reduces the common-mode part of the signal.
Frequency behavior in common-mode filtersIn the figure, the scattering parameter (S-parameter) describe the transmission coefficients, the ratio between the incoming and outgoing signal.
0.1 1 10 100 1000 10000 frequency (MHz)
0
Differential Mode Pass-Band
-3 dB loss
Atte
nuat
ion |S
21| (
dB)
Common-mode Pass-Band
Common-mode (noise) S-Parameter S21cc Differential Mode (signal)
S-Parameter S21dd
Differential mode signals will pass the filter
Unwanted Common-mode signals are attenuated
Common-mode filter
9
1. Two challenges: ESD and EMI
Frequency bands used in mobile devicesPortable devices operate within a wide spectrum of wireless frequency bands. A good common-mode filter has strong common-mode rejection for all these bands.
In all these bands, interference with other signals can cause EMI issues.
NXP PCMFxDFN1 filtersThe NXP family of PCMFxDFN1 common-mode filters with integrated ESD protection delivers exceptional common-mode rejection (CMR) throughout the mobile frequency range. CMR performance in the critical GSM, 3G, LTE, and WiFi bands is particularly good.
In practice, ferrite-based common mode have more narrow-band CMRs, hence they suppress only a part of the critical frequency bands, while PCMFxDFN1 covers all critical frequencies with strong rejection.
1E91E81E7 8E9
-30
-25
-20
-15
-10
-5
-35
0
freq (Hz)
Scc21 (dB)
PCMFxDFN1
be�er
CMR offerrite-basedCMFs
Common-Mode relevant frequencies
1,00E+08 1,00E+09 1,00E+10
Frequency (Hz)
Bluetooth
WiFi
LTE
GSM/3G
GPS/GLONASS
GSM 900 – up 890-915 MHz GSM 900 – dwn 935-960 MHz GSM 1800 – up 1710-1785 MHz GSM 1800 – dwn 1805-1880 MHz
GSM 850 – up 824-849 MHz GSM 850 – dwn 869-894 MHz
GSM 1900 – up 1850-1910 MHz GSM 1900 – dwn 1930-1990 MHz WIFI 2.4 – 2.5 GHz WIFI 4.9 – 5.8 GHz
LTE 700/800 MHz, 1700/1900 MHz LTE 900 MHz, 1.8, 1.9, 2.5, 2.6 GHZ
Bluetooth, 2.4-2.5 GHz GPS 1.2, 1.5 GHz, GLONASS 1.6 GHz
Common-mode relevant frequencies
10
2. Common-mode filters and the future of mobile
As faster data transfers become standard for mobile devices, common-mode filters need to maintain strong common-mode rejection in the range between 700 MHz and 5.8 GHz and, at the same time, offer differential pass-band close to the 3rd harmonics of the data.
Frequency (Hz)
Good common-mode rejection
is needed in this frequency range
1,00E+08 1,00E+09 1,00E+10
USB 2.0
HDMI 1.4
USB 3.0
HDMI 2.0
700 MHz – 5.8 GHz
Fundamental3rd harmonics
11
3. Filtering and protecting MIPI lines (PCMFxDFN1)
What are MIPI lines?To provide a flexible, high-speed serial interface for today’s high-resolution cameras and displays, the MIPI Alliance established the D-PHY interface. The camera interface is referred to as CSI, and the display interface is DSI.
The D-PHY interface is a low-voltage, differential-signal standard that supports high resolution cameras and displays. It limits the number of data lines and minimizes the energy required for data transport. The D-PHY interface also supports operation in the same frequency range required for GSM/3G/LTE/Wi-Fi transmission.
PCMFxDFN1 filtersNXP’s PCMFxDFN1 filters are designed to protect and filter designs that use MIPI D-PHY CSI or DSI. The top figure shows a typical configuration for MIPI CSI, and the bottom figures shows one for MIPI DSI.
aaa-007393
FLEX
FO
IL C
ON
NEC
TOR
PCMF3DFN1
SUPPLY,CONTROL
AND BACKLIGHT
FLEX FOIL
LIQUID CRYSTALDISPLAY
(LCD)
CLK_P
CLK_N
D0_P
D0_N
D1_P
D1_N
SYSTEM-ON-CHIP (SoC)
PCMF2DFN1
D2_P
D2_N
D3_P
D3_N
MIP
I LA
NE
MO
DU
LE
FLEX
FO
IL C
ON
NEC
TOR
PCMF2DFN1(PCMF3DFN1)
SUPPLY ANDCONTROL
FLEX FOIL
CAMERAMODULE
CLK_P
CLK_N
D0_P
D0_N
D1_P
D1_N
SYSTEM-ON-CHIP(SoC)
MIP
I LA
NE
MO
DU
LE
aaa-007392
12
3. Filtering and protecting MIPI lines (PCMFxDFN1)
Why do MIPI lines need ESD protection?ESD can find its way to the MIPI data lines via air discharge, through gaps in the body of the mobile devices that accommodate the camera fittings, for example or even thin layers of plastic.
The main source of ESD is human contact, and the average device can be handled by a person several, if not dozens of times each day.
NXP’s PCMFxDFN1 filters have integrated ESD protection, so they can protect the data lines while also reducing the impact of common-mode noise.
Avoiding EMICreating a design that has good RF integrity helps to reduce EMI. This involves two aspects of development, the layout and the signal.
Lens system
Lens fitting
Sensor
Flex foilfor SoC connection
Layout aspects
Separate RF, analog, digital,and power blocks
Use straight, parallel routingto avoid discontinuities
Use boards with multiple (ground)layers
Use ofdifferential signals
Choose the right filters
Signal aspects
Design with good RF integrity
13
A closer look at the PCMFxDFN1 seriesThe PCMFxDFN1 series protects and filters MIPI CSI and DSI configurations in smartphones, tablets, and other portable devices. It can also be used with HDMI interfaces.
By delivering the widest bandwidth of common-mode suppression, the PCMFxDFN1 series offers the best insurance against EMI issues.
The PCMF2DFN1 protects and filters two differential pairs, the PCMF3DFN1 protects and filters three.
Key features Industry-leading common-mode suppression (> 14 dB in the range between 500 MHz
and above 8 GHZ) Very wide differential pass-band (> 2 GHz), ensuring signal integrity for all MIPI
frequencies Best-in-class system-level ESD protection due to deep snapback and > 15 kV contact
ruggedness against IEC61000-4-2 pulses Industry-standard footprint Very thin package: 0.5 mm (max)
Key benefits Minimized EMI emission and -susceptibility of the system Optimized ESD protection for the SoC makes the system robust Minimized impact on signal for easy system integration
PCMF2DFN1 for two differential line pairs
PCMF3DFN1 for three differential line pairs
3. Filtering and protecting MIPI lines (PCMFxDFN1)
14
Industry-leading common-mode suppressionCompared to ferrite- and other silicon-based common-mode filters, the PCMFxDFN1 family offers much wider and deeper common-mode suppression across the full range of possible EMI-critical frequencies and their higher harmonics.
RF performanceThe PCMFxDFN1 has a differential pass-band bandwidth of more than 2 GHz, which exceeds the requirements of the MIPI D-PHY standard.
1E91E81E7 8E9
-30
-25
-20
-15
-10
-5
-35
0
freq (Hz)
Scc21 (dB)
PCMFxDFN1
be�er
aaa-007663
106 107 108 109 1010f (Hz)
S21ddS21dd(dB)(dB)
-10.0
-7.5
-5.0
-2.5
0.0
1E91E81E7 8E9
-30
-25
-20
-15
-10
-5
-35
0
freq (Hz)
Scc21 (dB)
PCMFxDFN1
CM suppression with PCMFxDFN1 versus ferrite-basedcommon-mode filters
PCMFxDFN1 differential-mode pass-band (S21 dd)
CM suppression with PCMFxDFN1 versus silicon-basedsolutions from other suppliers
MIPI eye diagram at 1.5 Gb/s (max D-PHY data rate)
3. Filtering and protecting MIPI lines (PCMFxDFN1)
15
PCMFxDFN1 layout recommendationsThe figure gives a sample layout for a five-channel MIPI interface. The PCMF2DFN1 and the PCMF3DFN1 are connected to a flex-foil connector.
2 mm
Flex foilconnector
Separation of differentialline pairs by GND to supportRF performance and ESD protection
5 differentialMIPI line pairs,impedancecontrolled
3. Filtering and protecting MIPI lines (PCMFxDFN1)
16
IP3319CX6 filterNXP’s IP3319CX6 filter is designed for use with USB 2.0 and USB OTG. It is a single-channel common-mode filter with integrated ESD protection (up to 15 kV contact discharge), and is housed in a 0.4 mm pitch wafer-level chip-scale package (WLCSP6).
The filter also integrates two ultra-low capacitance rail-to-rail diodes for the differential data lines, plus a separate protection diode, for the ID-pin.
The IP3319CX6 delivers significantly higher common-mode rejection than a direct competitor. It also provides very strong common-mode rejection in the GSM900 spectrum, with signal integrity that is good enough to fully support USB 2.0 speeds.
USB 2.0, which is by far the most common interface for charging and data exchange in portable systems, can be found in most smartphones and tablets. The regular version of USB 2.0 uses one differential line pair and one supply line of 5 V, while the mobile version, dubbed On-The-Go or OTG, adds an extra line so the system can act as a USB host for devices like keyboards, printers, and other peripherals.
Although the nominal data rate for USB 2.0 is 480 Mbits/s, and the major part of the spectral power is below 480 MHz, significant power is still present around 960 MHz, which can interfere with systems operating near that part of the spectrum, including GSM-900 system. A common-mode filter can improve the situation by suppressing EMI from the GSM transmitter to the USB 2.0 data lines, and by reducing the impact of USB 2.0 emissions on the GSM receiver.
-25
-20
-15
-10
-5
0
1,E+06 1,E+07 1,E+08 1,E+09 1,E+10
S 21d
d M
ag (d
B)
f (MHz)
Common-mode rejection
4. Filtering and protecting USB 2.0 (IP3319CX6)
Other supplier
IP3319CX6
17
4. Filtering and protecting USB 2.0 (IP3319CX6)
IP3319CX6 Key features Very wide differential pass band > 1 GHz Very broadband common-mode attenuation Two-line (one differential channel) common-
mode filterESD protection for the USB ID line Extremely low clamping ESD protection,
excellent SoC protection ESD protection up to ±15 kV on external
contact pins Ultra-low ESD diode capacitance Also supports interfaces for LVDS and DVI
Very small WLCSP6 package (1.6 x 1.15 x 0.65 mm) with 0.4 mm pitch
IP3319CX6 insertion losses for differential and common-modes
Typical IP3319CX6 application using Micro USB connector Type B
aaa-006138
105 106 107 108 109 1010-30
-24
-18
-12
-6
0
f (Hz)
αilαil(dB)(dB)
(1)(1)
(2)(2)
(1) Differential mode
(2) Common-mode
18
4. Filtering and protecting USB 2.0 (IP3319CX6)
IP3319CX6 USB 2.0 eye diagramThe eye diagram shows measurements using test template 5 on a test board with the IP3319CX6 at TP4 with limits of 300 mV.
IP3319CX6 layout recommendationsA good GND connection between pin C1 (GND) and the USB connector ensures optimized ESD protection. Shorter connections minimize resistive and inductive impedance.
Two sample layouts are shown. The lower layout uses a lower or bottom layer to connect the ID pin with the SoC. This makes a solid, low-ohmic, and low-impedance connection to pin C1 (GND).
time, ns
0.0
-0.4
-0.2
0.0
0.2
0.4
0.5 1.0 1.5 2.0
di�e
rent
ial s
igna
l, V
mask
Signal clearly in specification
19
5. A special situation: ESD protection for the SoC
ESD pulses need to be kept away from the System on Chip (SoC) while maintaining signal integrity for all the frequencies used by the application.
TLP measurementsTransmission-line pulse (TLP) measurements are the industry standard for gauging the effectiveness of ESD protection for an SoC. The TLP characteristic is measured using a series of increasing ITLP (VTLP) pulses. Each pulse is a point in the diagram. These pulses are generated by discharging a transmission line with a defined impedance of 50 Ω. The quality of protection for the SoC is shown by having a low TLP Voltage for a given TLP current.
The diagrams show that the NXP CMF common-mode filters provide a higher degree of ESD protection for the SoC. This is, in part, due to the deep snap-back characteristics of PCMF devices.
Measurement 1 shows, that the NXP PCMF Common Mode Filter provides SoC protection, which is more than one magnitude stronger compared to Ferrite based solutions with integrated ESD protection.
System
System on Chip (SoC) Connector ESD- protection
Signal lines
Clamped ESD pulse
Path of ESD-pulse
pulse
Internal ESD protection to allow safe assembly
IEC ESD
Measurement 1 Measurement 2
© 2014 NXP Semiconductors N.V.
All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The
information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and
may be changed without notice. No liability will be accepted by the publisher for any consequence of its use. Publication thereof
does not convey nor imply any license under patent- or other industrial or intellectual property rights.
Date of release: May 2014
Document order number: 9397 750 17547
Printed in the Netherlands
www.nxp.com