AN2574 - Microchip Technology

2021 Microchip Technology Inc. Under NDA DS00002574B-page 1

TABLE OF CONTENTS

1.0 Introduction .................................................................................................................................................................. 21.1 Overview .......................................................................................................................................................... 21.2 How to use this Document ............................................................................................................................... 21.3 Sensor Dimensions Considerations ................................................................................................................ 21.4 Construction Method ........................................................................................................................................ 31.5 3D Electrode Styles ......................................................................................................................................... 4

2.0 Sensor Area Design .................................................................................................................................................... 62.1 Stackup ............................................................................................................................................................ 62.2 3D Feed Lines .................................................................................................................................................. 92.3 Existing Driven Shield .................................................................................................................................... 112.4 ESD Shielding Ring ....................................................................................................................................... 122.5 Floating Conductive Islands (Laser Patterning) ............................................................................................. 122.6 Noise Shielding layers ................................................................................................................................... 13

3.0 FPC Design ............................................................................................................................................................... 143.1 FPC Position for Frame Style Sensors .......................................................................................................... 143.2 FPC Position for 4S1N Style Sensors ............................................................................................................ 163.3 3D FPC Placement ........................................................................................................................................ 173.4 FPC Basic Routing Rules .............................................................................................................................. 183.5 FPC Pinout .................................................................................................................................................... 193.6 Shield Layers ................................................................................................................................................. 193.7 FPC Contacts ................................................................................................................................................. 20

4.0 Host PCB Design ....................................................................................................................................................... 214.1 PCB Material and Thickness .......................................................................................................................... 214.2 Polyimide Stiffener ......................................................................................................................................... 214.3 Placement ...................................................................................................................................................... 214.4 Routing ........................................................................................................................................................... 214.5 Additional information ................................................................................................................................... 22

5.0 System Design .......................................................................................................................................................... 235.1 Influence of Grounded and Floating Objects ................................................................................................. 235.2 Floating Conductors ....................................................................................................................................... 235.3 Ground Planes and Metal Panels .................................................................................................................. 235.4 Distance of Electrodes from Ground .............................................................................................................. 235.5 Practical Examples ....................................................................................................................................... 245.6 Internal Grounding ......................................................................................................................................... 255.7 System Earth ................................................................................................................................................. 265.8 Sensitivity on the Back of the Sensor ........................................................................................................... 265.9 FPC Sensitivity ............................................................................................................................................... 265.10 Mechanical Stability and Vibrations ............................................................................................................... 265.11 Thermal Considerations ................................................................................................................................. 275.12 Air Streams .................................................................................................................................................... 275.13 Moisture ......................................................................................................................................................... 27

6.0 Schematics Design Guide ........................................................................................................................................ 286.1 Connecting the 2D/3D System to the Host .................................................................................................... 286.2 SDA and SCL Lines ....................................................................................................................................... 286.3 TS and CHG Lines ......................................................................................................................................... 286.4 Reset Lines .................................................................................................................................................... 29

Appendix A. Guidance on Dimensions and Routing ........................................................................................................... 31

Appendix B. Revision History .............................................................................................................................................. 33

AN2574

2D/3D Electrode Design Guide

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1.0 INTRODUCTION

1.1 Overview

The Microchip maXTouch® technology is a two-dimensional (2D) system that detects the X and Y position of a touch onthe surface of a capacitive touchscreen. The Microchip GestIC® technology is a three-dimensional system (3D) thatuses capacitive sensing to detect the X, Y and Z position of a hand in the space above the surface of the touchscreen.By combining these two technologies, it is possible for a single system to detect both two-dimensional touches on thesurface of the touchscreen and hand gestures in the three-dimensional space above a touchscreen.

The issues concerning the design of a two-dimensional capacitive touchscreen may be well understood, but the 3Dcapacitive tracking of a hand several centimeters above the surface of the panel requires additional considerations.Precise capacitive changes in the range of femtofarads must be detected, so the electrode design needs to be donewith special care to give sufficient sensitivity and also robustness against other signals or noise sources.

This document provides guidelines on designing electrodes for 3D gesture controllers and their integration with a 2Dtouch sensor, including the routing of the 3D feed lines.

For information on designing 2D sensors, including advice on sensor patterns, refer to the following:

QTAN0080 – maXTouch Sensor Design Guide

1.2 How to use this Document

This application note presents the design rules and guidelines for designing combined 2D and 3D systems. By followingthis advice, it should be possible to obtain the best performance for a project. In practical situations, however, deviationsmay be necessary because of various requirements and constraints (such as size, cost, material limitations, and so on).The aim, therefore, is to minimize the deviations and avoid lowering system performance too far.

1.3 Sensor Dimensions Considerations

2D/3D systems will work best when the touchscreen diagonal is between 6 and 10 inches. The maximum suggestedsensor diagonal length is 15 inches. Please contact your Microchip representative if you need to work with dimensionsoutside this range.

Small sensors will likely show the best linearity, while large sensors show better detection range.

As a rule of thumb, the maximum detection height will be approximately the same as the length of the shortest 3Delectrode in the design. Note, however, that performance must be checked on a project-by-project basis, and EMIcompliance reasons could put a strong limit on the achievable detection range.

DS00002574B-page 2 Under NDA 2021 Microchip Technology Inc.

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1.4 Construction Method

For the 3D system to operate, it is necessary to add some additional electrodes outside the 2D matrix. It is possibleeither to add the electrodes to the same sensor (see Figure 1), use an external frame style PCB (see Figure 2) or usean additional layer between the 2D sensor and the coverlay. Adding 3D electrodes to the same glass as the 2Delectrodes is the preferred option, since it will be more compact, more cost effective, easier to assemble, and less proneto misalignment and other mechanical problems.

FIGURE 1: 3D SENSOR ON SAME GLASS AS SCREEN

Housing

DisplayDisplay FPC

Glass2D Pattern 3D Electrode

2D/3D FPC

Glue


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FIGURE 2: 3D SENSOR ON DEDICATED PCB

1.5 3D Electrode Styles

When combining a Microchip GestIC sensor with a maXTouch touch sensor, the two-dimensional touch sensor needsto be extended with GestIC Rx electrodes placed around the touch area. 2D/3D systems support two 3D electrodestyles: Frame (see Section 1.5.1 “Frame Style”) and 4S1N (4 South, 1 North) (see Section 1.5.2 “4S1N (4 south, 1North) Style”).

The electrodes must be designed in a way so that the hand is detected by all electrodes at the same time. To this aim,due to electrical field distribution, the Frame style is preferred when the aspect ratio is roughly square, while the 4S1Nstyle is preferred above a 16:9 ratio.

Sensors above a 5:2 ratio should be avoided because of the large electric field difference between the electrodes.Please contact your Microchip representative if you need to evaluate a solution with a higher aspect ratio.

Note that the sensor can be rotated 90° or 180° to achieve a proper ratio (see Figure 4). This will have no impact onperformances as long as design rules are observed; the axes are simply swapped.

Top View

Side View


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1.5.1 FRAME STYLE

With the Frame electrode style four 3D electrodes are placed around the 2D sensor, with one on each of the four sides(see Figure 3).

FIGURE 3: 3D ELECTRODE STYLE: FRAME

1.5.2 4S1N (4 SOUTH, 1 NORTH) STYLE

With the 4S1N (4 south, 1 North) style, four 3D electrodes are placed along the bottom of the 2D sensor, with a fifthalong the top. Note that this arrangement can be rotated so that the 3D sensors are along other edges of the screen(see Figure 4).

FIGURE 4: 3D ELECTRODE STYLE: 4 SOUTH, 1 NORTH

FPC


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2.0 SENSOR AREA DESIGN

2.1 Stackup

When the 3D electrodes are on the same substrate of the 2D sensor, the construction materials, thickness and structureof the 2D area are generally a good starting point for designing the 3D area also. Additional rules are indicated in thefollowing sections.

When 3D electrodes are designed on an independent PCB, follow the indications given in Section 4.0 “Host PCBDesign”.

2.1.1 SHAPE

Generally speaking, electrodes should be simple rectangles, with 90° angles. Small partial cuts or slight changes alongtheir longest dimension (length) are allowed, but these should be limited to the equivalent of 20% of the shortestdimension (height).

Additionally, logos and part numbers can be engraved on the electrodes, since there will be negligible impact onperformances. Indeed, this can sometimes be preferable for other reasons, as in Figure 5.

2.1.2 PLACEMENT

To gain more space, electrodes can be moved as near the border as possible. Since they are large, manufacturingerrors will have little impact and normal rules applied to tracks can be somewhat overlooked.

Figure 5 shows that it is better to use the space to make electrodes wider and embed text inside the electrode ratherthan to lose space for text.

FIGURE 5: ELECTRODE PLACEMENT

2.1.3 DIMENSIONS

Electrodes should be placed near the sensor borders and surround the whole 2D touch sensor area.

The width of the 3D electrodes should generally be between 3 mm and 6 mm (see Appendix A). Wider electrodes willgenerally give better performances.

It is good practice to balance the length of opposing electrodes. Thus:

• For a frame style arrangement, the north electrode should be the same length and width as the south electrode, and the west electrode should be the same length and width as the east electrode. (see Figure 6)

WRONG: Electrodes are narrowedto make space for text

CORRECT: Text is placed inside electrodes so the electrodes can be wider


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FIGURE 6: BALANCING ELECTRODE SIZES – FRAME STYLE SENSOR

• For 4S1N style arrangement, the four electrodes on the same side to be the same length, width and spacing. The fifth electrode should match the total span of the other four electrodes. See Figure 7.

FIGURE 7: BALANCING ELECTRODE SIZES – 4S1N STYLE SENSOR

2.1.4 ELECTRODE ALIGNMENT FOR FRAME STYLE SENSORS

In a Frame style arrangement, a particular electrode should not “shade” a nearby electrode placed at 90° in order toreduce coupling and to avoid the wrong electrode detecting hand movement first. See Figure 8, and Appendix A for thedimensions.

FIGURE 8: ELECTRODE ALIGNMENT

WRONG: Electrodes are different widths CORRECT: Electrodes are the same width

WRONG: 1) 4N electrodes are of different sizes2) 1S electrode does not match the overall width of the 4N electrodes

CORRECT: 1) 4N electrodes are of equal sizes2) 1S electrode has a matching width

OR

WRONG: The West electrode "shades" the end of the South electrode CORRECT: Neither electrode "shades" the other


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2.1.5 ELECTRODES ON DIFFERENT LAYERS

Electrodes can be placed on different layers whenever this can simplify routing: generally speaking, this will notsignificantly compromise their signal balance.

2.1.6 ELECTRODE GAP FOR SIGNAL ROUTING

The space between the electrodes for signal routing to the FPC should be minimized (see Appendix A). Wheneverpossible, compact all the feed lines in the minimum space allowed by the production process, whilst trying to respectthe minimum specified distances from the 3D feed lines and other tracks.

FIGURE 9: REDUCING ELECTRODE GAP

2.1.7 OVERLAP OF ELECTRODES AND DISPLAY METAL BEZEL

If an underlying display has a metal bezel, this must be taken into account when designing the electrodes.

As a general rule, if the total stack-up gap between the bezel and electrodes is less than 1 mm, place the 3D electrodesabove the bezel so that there is no overlap (see Figure 10). Otherwise the metal will attenuate the received signal andpotentially exert thermal induced signal drift (see Section 5.11 “Thermal Considerations”).

If the stack-up gap is 1 mm or more (see Figure 11), the 3D electrode can be allowed to overlap with the metal bezel,provided that the minimum non-overlapping electrode width (dimensions A1 and A2 in Appendix A) is respected.

WRONG: No attempt is made to compact the linesas they pass between the electrodes, so the gap is large

CORRECT: The lines are compacted as they pass between the electrodes, so the gap is as small as possible


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FIGURE 10: 3D ELECTRODES ABOVE A METAL BEZEL – STACK-UP GAP < 1 mm

FIGURE 11: 3D ELECTRODES ABOVE A METAL BEZEL – STACK-UP GAP 1 mm

The same rules also apply to sensors with a ground shield layer (see Section 5.0 “System Design”).

2.1.8 CONDUCTIVE MATERIAL RESISTIVITY

The conductive material used for electrodes and feed lines must allow for an RC constant time to be below 200 ns.Given a typical capacitive load of about 20 pF, the maximum resistance from the device pin to the far end of theelectrodes must be below 10 kΩ.

Since electrodes are far larger than feed lines, the material used for the electrodes could have higher sheet resistance.For example, the electrodes could be made with transparent ITO and feed lines with lower resistivity metal depositionif the connection to the electrodes is done over the full length. If there is a choice, it is recommended to use materialswith lower sheet resistance.

2.2 3D Feed Lines

3D feed lines act as electrodes so route them with care. They can detect the hand and have an undesirable effect onthe measured signal. They are also susceptible to external noise pickup and crosstalk when running parallel to anelectrode (see Figure 13 below).

The following design rules apply:

• Make 3D feed lines as narrow as production process limits allow (ideally 30 to 50 μm), but bearing in mind total resistance (see Section 2.1.8 “Conductive material resistivity”). This is one of the most important rules, because a wider line will have more parasitic coupling to nearby ground or 2D lines, reducing sensitivity. Moreover, it will more easily pick up unwanted signals, reducing performance.

• Keep 3D feed lines as short as possible.

NOTE The metal Bezel of a display must be always grounded (see Section 5.6 “Internal Grounding”).

< 1mmDisplayBezel

1mm


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• If electrodes are placed on different layers, ensure that they are not crossing other lines. Crossover can be avoided by routing lines on the PCB behind the 2D/3D connector; see Section 4.4 “Routing” for details.

• If the gap between the feed line and an underlying display metal bezel is less than 1 mm, route the feed line in a way to avoid it running above the bezel for more than ~20 mm.

• If the feed lines are on another layer, never route below other electrodes as strong coupling could occur.

• Whenever possible, place 3D feed lines coming from other directions inside the 3D area, not outside. This will avoid the feed line picking up the signal before the electrode during a gesture (see Figure 12 and Figure 13). Note that this is not a problem for electrodes on the same side of the screen in the 4S1N style.

• Keep the feed lines distant from 2D signals and ground/shield traces, as coupling to 2D traces or ground will noticeably reduce sensitivity. See Appendix A.

FIGURE 12: ROUTING OF FEED LINES – ON A PCB

WRONG: Feed lines pass beneath the elctrodes and so can affect readings

CORRECT: Feed lines pass on the inside of elctrodes and so do not affect readings


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FIGURE 13: ROUTING OF FEED LINES – ON GLASS

2.2.1 CONDUCTIVE MATERIAL RESISTIVITY

The advice in Section 2.1.8 “Conductive material resistivity” for electrodes also applies to the 3D feed lines.

2.2.2 ROUTING NEAR OTHER SIGNALS (GROUND OR 2D SIGNALS)

For proper 3D operation, a guard track (either ground or a driven shield) between the 2D lines and 3D lines is notrequired, as the 2D lines are driven with TX signal during 3D cycles. A shield will not be beneficial to 3D sensing, but,in contrast, it will reduce further the distance between the 3D signals and “foreign” lines.

2.3 Existing Driven Shield

If a driven shield (typically DS0) is required for 2D touchscreen design, it is implemented as the outer track of thetouchscreen sense lines. Specifically, if the touch screen pattern is single-sided, the driven shield is routed around thetouch pattern as a loop inside the 3D electrodes area (see the blue driven shield loop in Figure 14). The 3D electrodesshould maintain a clearance of D1/D2 to the driven shield (see Appendix A).

The 3D electrodes and feed lines must be located well away from the driven shield: the driven shield is grounded during3D cycles, so it will attenuate nearby RX signals. The driven shield can, however, be used to shield 2D tracks in theusual manner for 2D-only systems.

WRONG: Feed lines pass under the electrodes and so can affect readings

CORRECT: Feed lines pass on the inside of the electrodes and so do not affect readings

WRONG: Feed lines pass on the outside of the electrodes and so can affect readings


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FIGURE 14: DRIVEN SHIELD (DS0) LOOP WITH A SINGLE-SIDED TOUCH SENSOR DESIGN

2.4 ESD Shielding Ring

Although an ESD shielding ring is usually recommended in a 2D-only system, it will definitely have a negative impacton 3D performance. A large ESD ring (or two, if placed on both sides of the sensor) will distort and reduce the signalseen by nearby 3D electrodes and attenuate the signals of the 3D feed lines running parallel to it.

• Check (on both sides) that the ESD shield is really the only way to avoid electrostatic discharges. For example, if sealing or sufficient distances from ESD sources can be achieved without a shield (such as, making use of the width of the front panel overlay), an ESD shield should be avoided.

• If an ESD ring cannot be avoided, it should be as thin as possible (see Appendix A). The ESD ring is a low impedance track that will intercept all electric discharges and will perform even if it is very thin, so there is no need for a large track. In addition, place the ESD ring as far as possible from the 3D electrodes and feed lines (see distance D1 in Appendix A).

• Note that ESD protection diodes on the GestIC RX lines should also be avoided. If ESD protection diodes are planned, ensure that low capacitance, low leakage devices are used. Diodes leakage could reduce detection considerably. Additionally, capacitance and leakage changes due to temperature variations could induce signal drifts and, as a consequence, impair detection. When in doubt, verify performance with and without the diodes present.

2.5 Floating Conductive Islands (Laser Patterning)

Floating conductive areas resulting from some “subtractive printing” sensor technologies (such as laser patterning usedfor ITO layer ablation), while mostly not harmful to 2D detection, can be detrimental to 3D sensing since they could actas a capacitive-conductive bridge between the 3D signals and other tracks on the sensor. Note that connecting theseareas to ground will still have a negative impact due to signal absorption.

For best performance when using such production methods, make sure that the total etched (non-conductive) areabetween a 3D signal and all other signals will still respect the values indicated in Appendix A (see Figure 15).Additionally, break up the floating area into small sections (using 500 µm as a typical dimension, as for 2D designs)

interrupt the floating area multiple times to stop the signal bridging. If this becomes an impractical process due to thelarge area to be removed, conventional photolithographic etching or direct conductive printing could be better suited to2D/3D sensor applications.


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FIGURE 15: FLOATING ISLANDS

2.6 Noise Shielding layers

If an electrically conductive noise shielding layer is used on the back of the touch sensor, the same rules apply as for ametal bezel to avoid excessive signal attenuation (see Section 2.1.7 “Overlap of electrodes and display metal bezel”).

CORRECT: Etching/ablation must preserve the distances indicated in this guide

WRONG: Floating islands are too close


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3.0 FPC DESIGN

3.1 FPC Position for Frame Style Sensors

For frame style sensors, the optimum position for the FPC connector is on the corner with the lowest probability of ahand presence. If there is an obvious location for a hand to rest, the connection point for the FPC should be at theopposite side from a possible resting hand. For example, if the hand typically rests on the lower edge of the device, theFPC should be on the upper edge. This will reduce the influence of the hand on the FPC itself.

Figure 16 shows the lower part of an automotive console that consists of a 3D touch panel with buttons below the touchpanel. When operating the buttons, the user’s hand is close to the lower edge of the touch panel, so the preferredposition for the FPC connector is on the top edge of the touch panel.

FIGURE 16: SCREEN WITH BUTTONS ON THE LOWER EDGE

Preferred position for tail: corner on

the top side


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Figure 17 shows how a corner position for the FPC is preferred for a sensor with a combined 2D/3D format. In the lefthand example, the feed lines for the West and South electrodes pass below the North electrode. In the right handexample, by positioning the FPC on the corner, these feed lines do not need to pass by the North electrode. The Eastelectrode, however, still has to pass on the inside of the North electrode in both arrangements, and this cannot beavoided.

On a composite 2D/3D sensor, as shown in Figure 17, placing the FPC in the corner also avoids the need to divide theNorth electrode into two parts, which could cause a deformation in the received electric field at the center of the sensor.

FIGURE 17: PLACEMENT OF FPC ON A FRAME STYLE SENSOR – COMBINED 2D/3D

Figure 18 shows FCP placement when a separate PCB is used. The main difference is that the North electrode doesnot need to be divided if the FPC is placed centrally (there is no need to route the 2D sense lines). However, it is stillimportant to consider the placement of the FPC and feed lines. In the right hand example, the West and South electrodefeed lines do not pass the North electrode, as the FPC is positioned on the corner. In addition, the East electrode feedline passes on the inside of the North electrode.

If there is no way to place the FPC on a corner, the gap between the two sections of a split electrode must be as smallas possible to limit performance loss. The maximum distance depends on the sensor size, and guidance is given inSection Appendix A: “Guidance on Dimensions and Routing”. Note that the specified minimum distance between the2D lines and the two halves of the electrode (indicated in the same appendix) must always be observed.

It is recommended to avoid connecting the two half electrodes with a "bridge" on the sensor or on the FPC, sinceexcessive coupling to 2D lines could occur. The preferred way to implement an electrical connection is with a track onthe PCB hosting the GestIC device.

FPCFPC

WRONG: FPC in the middle: West and Southfeed lines pass inside North electrode

CORRECT: FPC on one side: West and Southfeed lines do not pass by North electrode


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FIGURE 18: PLACEMENT OF FPC ON A FRAME STYLE SENSOR – SEPARATE 3D

3.2 FPC Position for 4S1N Style Sensors

For 4S1N sensors, the preferred position for the FPC is in the center of the panel. The feed line for the additional (North)electrode should be routed around the inside of the 2D sensor so that it does not interfere with the X position algorithm(see Figure 19).

FIGURE 19: PLACEMENT OF FPC ON A 4S1N STYLE SENSOR

2D FPC

North

South

Wes

t

East2D Touch Matrix

3D FPC

2D FPC

South

Wes

t

East2D Touch Matrix

3D FPC

North

WRONG: FPC in the middle: West, South and Eastfeed lines pass alongside North electrode

CORRECT: FPC on one side: West, South and Eastfeed lines do not pass alongside North electrode

FPC


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3.3 3D FPC Placement

When the 2D and 3D FPCs are separate, make sure that the 3D sensor FPC does not overlap with either the displayFPC or the 2D FPC. There should always be at least 10 mm between the 3D FPC and display cables, and 2 mmbetween the 3D FCB and 2D FPC, to avoid unwanted coupling.

FIGURE 20: FPC CONNECTION

2D Touchscreen

Display

Display

3D Electrode

>2mm

2D FPC3D FPC

3D Electrode

3D FPC

2D FPC

DisplayFPC

X

WRONG: 3D FPC overlaps 2D FPC and Display FPC

>10mm

3D FPC

2D Touchscreen

>2mm

2D FPC

Display

Display

3D Electrode

CORRECT: FPC connectors do not overlap


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3.3.1 SPACE FOR 2D FPC

When the 3D sensor is on a separate PCB, it is important to route the FPC for the 2D touch sensor panel below the 3Dsensor so that it does not cover the 3D electrodes. In Figure 21 there is a cutout to allow the FPC to be routed correctly,giving the FPC enough space for a soft bend. Figure 22 shows a bad example in which the FPC for the 2D touch sensorpanel is pinched between the cover glass and the 3D sensor, thus causing the FPC to shield the 3D electrode.

FIGURE 21: CROSS SECTION OF CORRECTLY PLACED FPC BELOW 3D SENSOR PCB

FIGURE 22: INCORRECT PLACEMENT OF 2D FPC IN RESPECT TO 3D PCB

3.4 FPC Basic Routing Rules

From a signal perspective, you can consider the FPC simply as a “flexible extension” of the glass. This means that thedesign rules for glass should be followed for the FPC (see Section 2.2 “3D Feed Lines”). In addition:

• FPC length should be as short as possible.

• 3D RX signals must not be crossed with other signals on the FPC due to the thin substrate. When signal crossings are necessary, consider crossing the signals on the PCB, as the PCB is typically thicker than the flex substrate and results in a lower capacitive load, see Section 4.0 “Host PCB Design”.

• Use the maximum available space to keep the 3D feed lines away from other tracks (see Figure 23).

FIGURE 23: MAXIMIZING 3D TRACK SEPARATION

Display

Touch Sensor 3D Sensor

Cover GlassHousingHousing 3D

Sensor

FPC

Cutout for FPC

Display

Touch Sensor Cover Glass

Housing

FPC

3D Sensor

PCB

Maximize distances

PCB

WRONG: 3D Feed lines are to close CORRECT: 3D Feed lines follow spacing rules

No Connection

3D Electrodes2D Electrodes

ey:

GND/Shield


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3.5 FPC Pinout

Since the 3D electrodes and feed lines should not cross 2D lines on the glass or FPC, in most designs the 3D feed lineswill be placed at the periphery of the FPC. However, if there are ESD shield connections, then these should be placedoutside the 3D electrodes. Note that there should be a gap between the 3D electrode feed lines and any ESD shieldconnections.

For a good signal separation on the FPC, leave one or two unused contact pads between the 3D lines and any othersignals. This applies to the connectors on both the PCB and display ends of the FPC.

FIGURE 24: LEAVING FREE PADS ON FPC CONNECTOR TO IMPROVE SIGNAL SEPARATION

3.6 Shield Layers

A shield layer, whether copper, carbon or any other conductive material, should not cover the 3D lines. Since thethickness separating the shield from the tracks is just some tens of microns, the 3D signals will be strongly attenuatedor cross coupled. The shield should therefore be trimmed to cover just the 2D lines (see Figure 25).

FIGURE 25: SHIELD LAYER

NC between 3D electrode pins and 2D/GND pins

Display

PCB

NC (No Connection)


Key:

GND/Shield


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3.7 FPC Contacts

Plating materials used for the FPC contact area should be compatible with the mating side (connector or glassdeposition):

• Thermoelectric effects could be very detrimental to 3D operation, generally showing up in systems as sudden signal offset change on one or more RX channels. This is due to the extreme sensitivity of 3D system to even small relative changes of RC constant of RX lines.

• Electromigration effects could permanently stop operation due to increased contact resistance.

If an FPC connector is used, it is strongly recommended to use gold plating on both the FPC and the connector contacts.


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4.0 HOST PCB DESIGN

4.1 PCB Material and Thickness

The usage of good quality FR4 is suggested. Highly hygroscopic materials like CEM1 should be avoided.

To exclude vibration-induced microphonic effects, and to guarantee a minimum distance between 3D feed lines andmetal parts below the PCB, the total PCB thickness should be 1 mm or greater.

Thin polyimide foils, resulting from the extension of the FPC, can be used with a stiffener (see Section 4.2 “PolyimideStiffener”).

4.2 Polyimide Stiffener

When using polyimide as a PCB, take care to use FR4 as a stiffener, and not metal, as the small distance to a conductiveplane could couple significantly to 3D electrodes feed lines and substantially attenuate the signals.

FIGURE 26: POLYIMIDE STIFFENER

4.3 Placement

3D feed lines are very sensitive to noise, and therefore routing to the GestIC device should be as short as possible.Consequently, if a decision must be taken on how to place the GestIC device and the maXTouch device, place theGestIC device nearest to the sensor connector.

4.4 Routing

Most of the rules applied to sensor design applies here also:

• 3D feed lines should be kept as short as possible.

• 3D feed lines should be as thin as possible. A width of 0.08 mm or lower is recommended. The maximum allowed width is 0.15 mm.

• Do not allow any other signal to cross or pass over the 3D feed lines.

• There should be no ground plane below the 3D feed lines. If this should be absolutely necessary, make sure there is at least 1 mm vertical distance from the feed lines to the ground plane underneath.

• Whenever possible, the 3D feed lines should be kept at least 2 mm from any other signal line. See also Section 5.0 “System Design”.

• The distance between the 3D feed lines should be at least 1 mm. If the total feed line length is below 20 mm, a distance of 0.5 mm from other 3D lines is admissible.

• It is possible to avoid crossover of the 3D lines with other signals passing behind the back of the 2D/3D connector. See the concept layout in Figure 27.

Metal

Polyimide

FR4

Polyimide


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FIGURE 27: ROUTING OF 3D LINES BEHIND THE CONNECTOR TO AVOID CROSSOVERS

4.5 Additional information

For additional information on PCB design, please refer to the relevant GestIC and maXTouch datasheets.

GestIC

maXTouch

3D Lines NOT shielded and not overlapping other linesrouted on the bottom layer of the PCB

2D Lines


Key:


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5.0 SYSTEM DESIGN

5.1 Influence of Grounded and Floating Objects

Because of their sensitivity, the tracks must be routed with the maximum distance to foreign signals, especially fromthose on nearby PCBs. Routing 3D feed lines near AC signals (for example, communication lines, AC/DC converters,and so on) must be avoided, and a ground shield should be used if necessary. Generally speaking, 3 mm is a sufficientdistance from TTL level signals. A greater distance may be necessary if high power is involved.

Routing next to ground rather than AC signals is always preferred, but note that shielding the RX signals will result inthe loss of sensitivity.

5.2 Floating Conductors

Floating conductors must be kept outside the sensitive area. Floating conductive parts act as expansions of the 3D RXelectrodes, falsify the gesture detection and add noise to the system. This is more important the closer the conductorsare to the RX electrode. If a foreign conductive object is not avoidable, it must be connected to device ground (seeSection 5.3 “Ground Planes and Metal Panels”.

5.3 Ground Planes and Metal Panels

The electric field generated by the 2D TX electrodes area needs to be detected by 3D electrodes. Ideally, it should freelyspread around the sensor area for best performances.

In practical circumstances, it will be greatly attenuated by nearby grounded objects, and the system should be designedto reduce as much as possible this negative influence.

5.4 Distance of Electrodes from Ground

The area around the RX electrodes has a major effect on the detection range. The distance between the 3D RXelectrodes and ground (for example, a grounded metal bezel around the display or a shield layer on the sensor glass)should be maximized.

In particular, ground areas placed above or beside the RX electrodes will absorb the electrical field more strongly andwill thus be worse than ground areas placed below the RX electrodes.

The effect of a nearby ground layer on the field distribution can be seen comparing Figure 28 and Figure 29. InFigure 29, where an additional ground layer has been added, the electric field distribution has been distorted andweakened compared to Figure 28.

FIGURE 28: ELECTRIC FIELD UNRESTRICTED BY GROUND PLANES

TX (Touch Area) RX

Ground Plane

Substrate Glass

Cover Glass


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FIGURE 29: ELECTRIC FIELD DEGRADED DUE TO GROUND PLANE PROXIMITY

5.5 Practical Examples

This section gives some practical examples that show how nearby ground planes can influence the signal.

With reference to Figure 30, there are two ways in which the distance between the 3D electrode and the GND layer caninfluence the detected signal. These are shown in the following examples.

EXAMPLE 1: VARIATION OF SUBSTRATE THICKNESS

Substrate thickness can have a strong influence when there is a ground layer on the back. For example, if an FR4substrate thickness is reduced from 1.6 mm to 0.5 mm, the signal amplitude is halved and the detection range isconsequently decreased by 30% to 50%.

EXAMPLE 2: VARIATION OF GROUND OVERHANG

With an FR4 substrate of 0.5 mm, if the ground layer extends 3 mm over the RX electrode instead of 1 mm, the signalamplitude is again halved, resulting in a further 30% to 50% reduction in the detection range.

FIGURE 30: EFFECT OF GROUND PLANES ON THE BACK OF THE SENSOR

The housing material also has an influence. A metallic housing brings additional ground in the sensor proximity thatreduces the detected signal.

EXAMPLE 3: CONDUCTIVE HOUSING

Figure 31 shows a setup with a metallic housing at 15 mm distance. In this case, the signal is approximately 40% lowerthan in a system with a plastic housing.

RXSubstrate Glass

Cover Glass

Ground Plane

Ground Plane

TX (Touch Area)

Ground Plane

Substrate thickness 0.5 mm vs 1.6 mm

TX (2D Touch Area)

FR4 Substrate

RX

Ground plane extension 1 mm vs 3 mm


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FIGURE 31: EFFECT OF CONDUCTIVE HOUSING ABOVE THE SENSOR

5.6 Internal Grounding

To avoid noise injection to 3D RX electrodes, it is very important that all system components share a common ground.

A non-exhaustive checklist of components to ground together is:

• 2D/3D touch controller board

• Display bezel and all its metal parts

• Display driver board

• Display backlight and backlight circuitry

• System power supply

FIGURE 32: INTERNAL GROUNDING

A metal bezel around the display must always be grounded, as shown in Figure 33. Use soldered wires or screws forthis purpose. Adhesive copper tapes are unreliable as a means to connect GND to the metal bezel and therefore shouldbe avoided.

Ground Plane

Substrate:1.6mm

TX (2D Touch Area)

FR4 Substrate

Cover GlassRX

1 mm15 mm

Conductive Housing(Grounded)

Display

PowerSupply

DisplayDriver

Touch Controllerand 3D Device


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FIGURE 33: DISPLAY BEZEL GROUNDING

5.7 System Earth

It is highly recommended that the system ground discussed in Section 5.6 “Internal Grounding” is referred to earth,following the applicable safety and EMC normative (this will always overrule any advice in this application note). Anunearthed 2D/3D system will likely show “baseline” variations, with low noise immunity and generally poor performance.This is especially true for small size and/or plastic housed devices.

For this reason, untethered battery-powered systems are not recommended when implementing 3D sensing.

5.8 Sensitivity on the Back of the Sensor

From the sensor’s point of view, there is virtually no difference if a hand is moved in front or behind the sensor. Ingeneral, the sensitivity is minimized by the presence of the display. If sensitivity of the back of the sensor is a concern,a conductive shield can be used. The same applies if unwanted sensitivity is present on the sides of the system.

5.9 FPC Sensitivity

As discussed in Section 2.2 “3D Feed Lines”, FPC 3D lines will be sensitive to nearby conductive objects. Verify thatthe system does not “react” to the manipulation of touchable parts of the housing in proximity of the FPC. If necessary,move the FPC and/or interpose some shielding.

5.10 Mechanical Stability and Vibrations

A mechanically stable setup is important to avoid signal drift caused by the deformation and relaxation of flexiblematerials.

If vibrations can change the distance from the 3D sensor to any other object (conductive or non-conductive),performance is affected. This can lead to a lower detection rate and bad baselining, resulting in a perceived shift in thehand position.

5.10.1 FPC STABILITY

The 3D FPC is very sensitive to vibrations. Make sure that the 3D FPC does not move when the device is subjected toany expected mechanical environment during operation. Electronic grade sulfur-free silicone glue or soft foam damperscan be used to mitigate the problem.

5.10.2 MOVEABLE SENSORS

A 3D sensor mounted on a moveable part (for example, a terminal with pan-tilt ability) cannot distinguish between itsown movement and a “hand” movement. Moving the sensor will in most cases result in a temporary “3D blindness”. Ona correctly tuned system this will typically last just a few seconds, thanks to the automatic recalibration. If this adjustmentproves to be insufficient, it is recommended to install a low cost SMD accelerometer so that the host system can detectthe movement and force a 3D recalibration.

Cover Glass

Metal bezel of displaymust be connected to

GND!

Sensor Glass

Display

3D Electrode


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5.11 Thermal Considerations

Fast temperature changes could lead to signal drifts due to the dependency of dielectric materials on temperature.Localized changes can be particularly detrimental, since signal shifts at different electrodes would not be balanced. Highpower devices and cooling systems should be checked to avoid this kind of influence.

5.12 Air Streams

Make sure that those places where 3D lines are routed (on the sensor, FPC and PCB) are protected from strong aircurrents (for example, system cooling fans), as these could affect 3D system operation due to temperature effects.

5.13 Moisture

The area above the 3D RX electrodes is very sensitive to capacitive changes. Moisture can bridge the signal from TXto RX, making the system sensitive to environmental changes. This problem can become particularly evident indemonstration mock-ups, where this issue is generally overlooked.

The effect of moisture therefore needs to be reduced by sealing the RX electrodes.

The left hand example in Figure 34 shows a bad example in which a 3D PCB is placed below an air gap between thehousing and the cover glass. Here, moisture can infiltrate and reach the RX electrode, thus bridging the signal from TXto RX. The dotted arrow in shows the capacitive coupling between TX and RX via the dielectric of the cover glass. Thiscoupling is always present and does not harm the 3D sensing. The solid arrow shows an additional signal path that ismodulated by moisture and/or humidity. This can change rapidly, for example by breath. This unpredictable additionalcoupling is undesirable and needs to be suppressed by sealing the 3D RX electrodes.

The right hand example in Figure 34 shows a good example of sealing the 3D RX electrode against the effects ofmoisture. In this example there is no air gap and the cover glass seals the RX electrode. Moisture therefore does notreach the PCB (3D RX lines) and the unwanted effect is very much reduced.

FIGURE 34: GAP BETWEEN HOUSING AND COVER GLASS

WRONG: There is an open gap between the housing and cover glass, so water can reach the PCB

CORRECT: The gap between the housing and cover glass is sealed, so water does not reach the PCB

TX

Display RX

Cover Glass

Sensor Glass

Moisture/Water

PCB

TX

Display RX

Cover Glass

Sensor Glass

Moisture/Water

PCB


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6.0 SCHEMATICS DESIGN GUIDE

This section addresses those points that will allow a smooth integration of 2D-3D system into your project. Note that itdoes not cover general aspects related to a good electronics design. Please refer to the device Datasheet for otheradvice, such as power supply decoupling, placement, soldering, and so on.

6.1 Connecting the 2D/3D System to the Host

The GestIC 3D Device can be connected to the host system through an I2C interface only, whereas the maXTouchdevice typically offers a choice of either SPI or I2C for connection to the host system.

For best performance it is recommended to separate the communication lines used by the GestIC and maXTouchdevices completely, connecting them to different pins on the host processor. However, if it is necessary to minimize therequired resources on the host, it is possible for both devices to share the same I2C interface, subject to the rules in thefollowing sections.

6.2 SDA and SCL Lines

6.2.1 COMMON I2C INTERFACE

If SDA and SCL are shared (that is, the same I2C interface is used for both the Gestic and maXTouc device), considerthe following points:

• If the bus bandwidth is exceeded, some communication packets will be lost, and this could result in missed gestures or touch events. This can happen, for example, when using debug data from the maXTouch device, or when using SD data from the GestIC device. Make sure that the host is configured to use the maximum SCL frequency allowed for the system (refer to the datasheets for the GestIC and maXTouch devices for their respective specifications).

In addition, to avoid excessive bus bandwidth usage and possible gesture/touch event loss, disable GestIC SD and/or CIC messages. Additionally, reduce the message output from the maXTouch device to those messages that are considered essential, and make sure that no debug data is output. Checking the bus with an oscilloscope could also help to verify the size of the load.

• 2D and 3D programming debug tools (such as, maXTouch Studio and the 3D Parameter Tuning tool) do not support a concurrently shared bus, as the tools can interfere with each other’s operation. This will mean inserting jumpers to allow separation of the bus to allow the concurrent operation of the tools, making debugging much easier (see Figure 35).

6.2.2 SEPARATE I2C INTERFACES

Separated SDA and SCL lines have the following advantages:

• Improved 3D noise performance

Separate I2C buses will avoid noise coming from communication with 2D device being injected into the 3D device.

• Improved bus bandwidth and minimum latency

As described in Section 6.2.1 “Common I2C Interface”, both the maXTouch and GestIC devices can, in some cases, use all the available bus bandwidth of a 400 kHz I2C bus.

• Programming/debug support

2D and 3D programming debug tools (such as, maXTouch Studio and the 3D Parameter Tuning tool) can be connected to the target board at the same time (see Figure 36).

6.3 TS and CHG Lines

The TS and CHG lines must not be shared: sharing the line would require additional polling to ascertain which devicerequires host attention, thus creating excessive delays. These lines must therefore be connected to separate host pinsso that the host knows which device has data, even if using a shared I2C bus.

IMPORTANT! When programming the devices or using debug tools (specifically, maXTouch Studio and the 3D Parameter Tuning Tool), the host must always be disconnected or have its lines configured to high impedance.


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6.4 Reset Lines

It is recommended that separate Reset lines are used for the maXTouch RESET line and the GestIC MCLR lines. If thisis not possible, and a single Reset line is used, a removable jumper will need to be inserted between the maXTouchRESET line and the GestIC MCLR line. This will allow the lines to be separated so that external programming ordebugging tools can be used (see Figure 35).

FIGURE 35: SCHEMATIC – SHARED COMMUNICATION INTERFACES (NOT RECOMMENDED)

Note 1: The value of the pull-up resistors will be chosen to ensure SCL and SDA rise and fall times meet the I2C specification. The value required will depend on the amount of capacitance loading on the lines.

2: Only the relevant pins are shown.3: Provided for debug purposes only. Not required for normal operation.

47kΩ100kΩ

(1)

10nF

VDD

(1)

(1)(1)

MCLR

SCL

SDA

TS47

GestIC

7

35

36

TS

654321

654321

SCL

SDA

RESET

CHG

maXTouchSDA

SCL

RESET

CHG

MXT Bridge Connector2.54mm pin strip (2)

6543

MGC Bridge Connector2 mm pin strip

10kΩ

10kΩ

VDD

ToHost

3 x 0Ω Resistors (3)


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FIGURE 36: SCHEMATIC – SEPARATE COMMUNICATION INTERFACES (RECOMMENDED)

Note 1: The value of the pull-up resistors will be chosen to ensure SCL and SDA rise and fall times meet the I2C specification. The value required will depend on the amount of capacitance loading on the lines.

2: Only the relevant pins are shown.

MCLR

SCL

SDA

TS47

10kΩ

MGC_TS

MGC_SDA

MGC_SCL

MGC_MCLR

10kΩ

MGC Bridge Connector2 mm pin strip

654321

654321

SCL

SDA

RESET

CHG

47kΩ

MXT_SDA

MXT_SCL

MXT_RESET

100kΩ

MXT_CHG

6543

10nF

ToHost

ToHost

7

35

36

VDD

VDD

(1)(1)

(1)(1)

MXT Bridge Connector2.54mm pin strip (2)

GestIC

maXTouch


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APPENDIX A: GUIDANCE ON DIMENSIONS AND ROUTING

The suggested dimensions discussed in this application note are summarized below.

General Tracks, FPC and Electrodes

4S1N Electrodes Distance(see Section 2.1.4)

Item Description Min Preferred Max

A 3D Electrode width(2) sensor size a 3 4 6

sensor size b 4 5 7

sensor size c 5 6 8

B 3D electrode to 3D electrode distance 1 2 6

C 3D electrode routing width See Note(3) 0.1

D1 Clearance of 3D electrode/routing to

• 3D electrode,

• other 3D electrode routing or

• shield line with width < 100µm

sensor size a 0.5 1 2

sensor size b, c 1 1.5 2

D2 Clearance of 3D electrode/routing to shield line with width > 100µm

sensor size a 1 2 4

sensor size b, c 2 3 4

E Clearance of 3D electrode/routing to 2D touch region (including all 2D signals) or plane(5)

sensor size a 1 3 10

sensor size b, c(4) 1 / 2 3 10

F Clearance of 3D electrode to RX or TX flex seal 3 – 30

G Distance between 2 electrodes if separated by routing to flex – – 20

D2A

B

C E

EE

F

B B


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Split Electrode (see Section 3.1)

Frame Electrodes Alignment(see Section 2.1.3)

Item Description Min Preferred Max

H Maximum total cutaway of electrode divided by routing to flex

sensor size a – – 15

sensor size b, c – – 25

IX, IY Overhang (shading) between electrodes at 90o (see Section 4.3 “Placement”)

sensor size a -1 0 2

sensor size b, c -1 2 6

Bottom LayerShield LayerMetal Bezel

Keep bottom layer clear under 3D electrodes. The specified minimum distance is the distance to ground. Without GND in the bottom layer, this can be the distance to the metal bezel of the display.

0.5(6) 1 –

Note 1: Use the maximum space available between 2D and 3D signals to avoid coupling between 2D and 3D signals.2: Size a: small sensors (6" diagonal or less) with minimized feed lines length and thin feed lines (50µm or less)

Size b: medium sensors (8" 12" diagonal) and thin feed lines (50 µm or less)Size c: large sensors (> 12") or all sensors with feed lines width >50 µm

3: Use the minimum width allowed by metal connection4: 1 mm allowed when length of total coupling distance for the given signals < 50 mm, otherwise 2 mm5: "plane": any floating, grounded or active shield conductive area larger than 3 mm x 3 mm6: See Section 2.0 “Sensor Area Design” for limitations related to distances < 1mm

North North

IY

IX


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APPENDIX B: REVISION HISTORY

Revision A (November 2017)

Initial edition

Revision B (July 2021)

Updated


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NOTES:


Note the following details of the code protection feature on Microchip devices:

• Microchip products meet the specifications contained in their particular Microchip Data Sheet.

• Microchip believes that its family of products is secure when used in the intended manner and under normal conditions.

• There are dishonest and possibly illegal methods being used in attempts to breach the code protection features of the Microchip devices. We believe that these methods require using the Microchip products in a manner outside the operating specifications contained in Microchip's Data Sheets. Attempts to breach these code protection features, most likely, cannot be accomplished without violating Microchip's intellectual property rights.

• Microchip is willing to work with any customer who is concerned about the integrity of its code.

• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of its code. Code protection does not mean that we are guaranteeing the product is "unbreakable." Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break Microchip's code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.

Information contained in this publication is provided for the solepurpose of designing with and using Microchip products.Information regarding device applications and the like is providedonly for your convenience and may be superseded by updates. Itis your responsibility to ensure that your application meets withyour specifications.

THIS INFORMATION IS PROVIDED BY MICROCHIP "AS IS".MICROCHIP MAKES NO REPRESENTATIONS ORWARRANTIES OF ANY KIND WHETHER EXPRESS ORIMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE,RELATED TO THE INFORMATION INCLUDING BUT NOTLIMITED TO ANY IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY, AND FITNESS FOR APARTICULAR PURPOSE OR WARRANTIES RELATED TO ITSCONDITION, QUALITY, OR PERFORMANCE.

IN NO EVENT WILL MICROCHIP BE LIABLE FOR ANYINDIRECT, SPECIAL, PUNITIVE, INCIDENTAL ORCONSEQUENTIAL LOSS, DAMAGE, COST OR EXPENSE OFANY KIND WHATSOEVER RELATED TO THE INFORMATIONOR ITS USE, HOWEVER CAUSED, EVEN IF MICROCHIP HASBEEN ADVISED OF THE POSSIBILITY OR THE DAMAGESARE FORESEEABLE. TO THE FULLEST EXTENT ALLOWEDBY LAW, MICROCHIP'S TOTAL LIABILITY ON ALL CLAIMS INANY WAY RELATED TO THE INFORMATION OR ITS USE WILLNOT EXCEED THE AMOUNT OF FEES, IF ANY, THAT YOUHAVE PAID DIRECTLY TO MICROCHIP FOR THEINFORMATION. Use of Microchip devices in life support and/orsafety applications is entirely at the buyer's risk, and the buyeragrees to defend, indemnify and hold harmless Microchip fromany and all damages, claims, suits, or expenses resulting fromsuch use. No licenses are conveyed, implicitly or otherwise,under any Microchip intellectual property rights unless otherwisestated.

Trademarks

The Microchip name and logo, the Microchip logo, Adaptec, AnyRate, AVR, AVR logo, AVR Freaks, BesTime, BitCloud, chipKIT, chipKIT logo, CryptoMemory, CryptoRF, dsPIC, FlashFlex, flexPWR, HELDO, IGLOO, JukeBlox, KeeLoq, Kleer, LANCheck, LinkMD, maXStylus, maXTouch, MediaLB, megaAVR, Microsemi, Microsemi logo, MOST, MOST logo, MPLAB, OptoLyzer, PackeTime, PIC, picoPower, PICSTART, PIC32 logo, PolarFire, Prochip Designer, QTouch, SAM-BA, SenGenuity, SpyNIC, SST, SST Logo, SuperFlash, Symmetricom, SyncServer, Tachyon, TimeSource, tinyAVR, UNI/O, Vectron, and XMEGA are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.

AgileSwitch, APT, ClockWorks, The Embedded Control Solutions Company, EtherSynch, FlashTec, Hyper Speed Control, HyperLight Load, IntelliMOS, Libero, motorBench, mTouch, Powermite 3, Precision Edge, ProASIC, ProASIC Plus, ProASIC Plus logo, Quiet-Wire, SmartFusion, SyncWorld, Temux, TimeCesium, TimeHub, TimePictra, TimeProvider, WinPath, and ZL are registered trademarks of Microchip Technology Incorporated in the U.S.A.

Adjacent Key Suppression, AKS, Analog-for-the-Digital Age, Any Capacitor, AnyIn, AnyOut, Augmented Switching, BlueSky, BodyCom, CodeGuard, CryptoAuthentication, CryptoAutomotive, CryptoCompanion, CryptoController, dsPICDEM, dsPICDEM.net, Dynamic Average Matching, DAM, ECAN, Espresso T1S, EtherGREEN, IdealBridge, In-Circuit Serial Programming, ICSP, INICnet, Intelligent Paralleling, Inter-Chip Connectivity, JitterBlocker, maxCrypto, maxView, memBrain, Mindi, MiWi, MPASM, MPF, MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient Code Generation, PICDEM, PICDEM.net, PICkit, PICtail, PowerSmart, PureSilicon, QMatrix, REAL ICE, Ripple Blocker, RTAX, RTG4, SAM-ICE, Serial Quad I/O, simpleMAP, SimpliPHY, SmartBuffer, SMART-I.S., storClad, SQI, SuperSwitcher, SuperSwitcher II, Switchtec, SynchroPHY, Total Endurance, TSHARC, USBCheck, VariSense, VectorBlox, VeriPHY, ViewSpan, WiperLock, XpressConnect, and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.

SQTP is a service mark of Microchip Technology Incorporated in the U.S.A.

The Adaptec logo, Frequency on Demand, Silicon Storage Technology, and Symmcom are registered trademarks of Microchip Technology Inc. in other countries.

GestIC is a registered trademark of Microchip Technology Germany II GmbH & Co. KG, a subsidiary of Microchip Technology Inc., in other countries.

All other trademarks mentioned herein are property of their respective companies.

© 2017 - 2021, Microchip Technology Incorporated, All Rights Reserved.

ISBN: 978-1-5224-8563-6

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AN2574 - Microchip Technology

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