prEN IEC 63758-5-4:2026

• Status: Not Published
• Publication Date: 23-Feb-2028
• Technical Committee: CLC/TC 100X - Audio, video and multimedia systems and equipment and related sub-systems
• Current Stage: 4020 - Enquiry circulated - Enquiry
• Start Date: 18-Sep-2026
• Completion Date: 18-Sep-2026
• Directive: 2014/53/EU - Directive 2014/53/EU of The European Parliament and of the Council of 16 April 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of radio equipment and repealing Directive 1999/5/EC
• Mandate: M/607 - COMMISSION IMPLEMENTING DECISION of C(2025)1207 on a Standardisation Request M/607 as regards charging interface and charging communication protocol for radio equipment capable of being recharged by means of wireless charging in relation with Article 3(4), sixth subparagraph, of Directive 2014/53/EU of the European Parliament and of the Council.
• Ref Project: oSIST prEN IEC 63758-5-4:2026 - Qi specification - Version 2.3 - Part 5-4: Mpp - Foreign object detection (Fast Track)

prEN IEC 63758-5-4:2026 is a CLC Committee Draft for Vote for the Qi specification, Version 2.3, Part 5-4. It specifies Foreign Object Detection (FOD) methods for MPP wireless power transfer, for Power Transmitter and Power Receiver implementations that need to detect and manage metal objects in the coupling field.

What does prEN IEC 63758-5-4:2026 specify?

prEN IEC 63758-5-4:2026 defines how Qi MPP systems detect foreign objects before and during power transfer, and how they react when an object could overheat. The document is organized as a general front section, followed by the pre-power-transfer, in-power-transfer, and calibration-based methods that make up the FOD approach.

• Clause 1 covers the general rules for reading the specification, including compliance language, numeric notation, packet field ordering, and shorthand notation.
• Clause 2 explains the FOD background and how the different methods are combined for sequential placement and in-transfer detection.
• Clause 3 describes the Open-air Q-Test before power transfer.
• Clause 4 describes the MatedQ-DeflectionTest before power transfer when a Power Receiver is present.
• Clause 5 describes MPP Power Loss Accounting (MPLA) during power transfer.
• Clause 6 describes MPLA improvements for Power Modes (MPLA2).
• Clause 7 describes DPLOSS, the calibration-based in-transfer method used to extend detection to higher power.
• Clause 8 gives nominal GG values for the MPLA, MPLA2, and MatedQ coefficient sets.

What are the key requirements of prEN IEC 63758-5-4:2026?

prEN IEC 63758-5-4:2026 combines pre-power-transfer detection, in-power-transfer monitoring, and calibration rules so a Power Transmitter can reduce or stop power before a foreign object becomes hazardous. In practice, implementers need to treat the methods as a coordinated safety system, not as separate optional features.

General rules and packet handling

Clause 1 states that the provisions are mandatory unless they are marked as recommended, optional, note, example, or informative. It also fixes the notation for numbers, tolerances, big-endian packet fields, text strings, and shorthand packet references. That matters because the FOD methods rely on exact parameter exchange and exact interpretation of packet data.

Open-air Q-Test before power transfer

Clause 3 defines the Open-air Q-Test as a comparison between the transmitter’s runtime Q measurement and its stored free-air reference. The test is used to detect a foreign object on the transmitter before power transfer begins, and it can be run periodically during standby. The movement timer and settling timer are there to avoid false foreign-object flags while a Power Receiver is being placed.

Clause 3 also makes the practical response clear: if the Open-air Q-Test is not implemented, the transmitter must set the open-air foreign-object flag so the in-power-transfer method knows it is working without pre-checks. If communication fails after digital ping, or if a foreign object is detected within the critical radius, the flag is set. In practice, this lets the transmitter limit negotiated power before charging starts.

MatedQ-DeflectionTest with a Power Receiver present

Clause 4 uses the same Q-based measurement concept, but with a mated Power Receiver and per-unit calibration. The Power Receiver sends MATEDQ_COEFF parameters during the negotiation phases, and the Power Transmitter uses the settled Open-air Q measurement as the starting point for MatedQ calculations. This matters because the transmitter is no longer deciding only from a free-air baseline - it is comparing the actual paired system against calibrated expectations.

Clause 4 also requires the transmitter to set the foreign-object field in MATEDQ_RES when a foreign object is in a position that would lead to overheating, and it must not enter DeltaPloss calibration if a foreign object is detected. In practice, that prevents a system from calibrating itself around an unsafe condition.

MPLA during power transfer

Clause 5 introduces MPLA as the in-power-transfer method for detecting foreign objects while power is flowing. The method estimates foreign-object power by comparing transmitted and received power, while separating coil, circuit, and friendly-metal losses and using ecosystem scaling so arbitrary transmitter-receiver pairs can be paired. For engineers, this means the design must support parameter exchange, loss modelling, and current measurement, not just a simple power subtraction.

Clause 5 also defines the power-control response. If the estimate indicates a foreign object, the transmitter must reduce transmitted power within a limited time, and while it is throttling it must answer PLA packets with NAK and hold or reduce inverter voltage. In practice, the transmitter is expected to fall back to a safe negotiated level rather than keep charging at the same rate.

MPLA2 for higher-accuracy power-mode operation

Clause 6 updates the in-power-transfer model for PLA Format 2. MPLA2 keeps the same overall purpose as MPLA, but uses a revised friendly-metal loss model that accounts for changing rectified voltage and current. The transmitter and receiver exchange the new parameters through PLA_2 packets, and the same safe throttling behaviour applies if a foreign object is present.

This matters for higher-power operation because the document uses MPLA2 to improve the fit of the power-loss estimate in power modes where the original model is less accurate. For implementers, that means the negotiation, packet format, and loss model must all match the selected power mode.

DPLOSS calibration and fallback

Clause 7 defines DPLOSS as a calibration-based method for tracking changes in compensated power loss during transfer. The Power Receiver calibrates at startup with multiple power levels and a minimum number of accepted calibration points, and the transmitter uses the resulting plane to watch for changes during operation. In practice, this is the method that extends FOD monitoring above the lower-power range, but only when calibration completes successfully.

Clause 7 also defines the fallback behaviour. If calibration is not available or a threshold is exceeded, the system reverts to the lower guaranteed power level and invalidates the calibration. That makes calibration quality a safety issue, not just a tuning task.

What terms does prEN IEC 63758-5-4:2026 define?

• Power Transmitter (PTx) - The charging-side device that measures Q, negotiates power, and applies foreign-object protection actions.
• Power Receiver (PRx) - The device being charged that reports coefficients, measurements, and power data back to the PTx.
• Foreign Object Detection (FOD) - The set of methods used to detect metal objects in or near the magnetic field so power can be limited before overheating occurs.
• Open-air Q-Test - The pre-power-transfer method that compares the transmitter’s Q in free air with its runtime Q to detect a foreign object before a receiver is mated.
• MatedQ-DeflectionTest - The pre-power-transfer method that uses paired transmitter-receiver measurements and calibration data to detect a foreign object when the receiver is present.
• MPLA - MPP Power Loss Accounting, the in-power-transfer method that estimates foreign-object power from transmitted and received power and related loss terms.
• MPLA2 - The updated MPLA model for PLA Format 2, with revised friendly-metal loss handling.
• DPLOSS - Delta Ploss, the calibration-based method that monitors changes in compensated power loss during power transfer.

Who uses prEN IEC 63758-5-4:2026?

prEN IEC 63758-5-4:2026 is used by engineers and technical teams working on Qi MPP wireless charging products. That includes transmitter and receiver designers, firmware developers, validation labs, quality managers, and certification teams.

In practice, they use it to choose the right FOD method, set thresholds, design packet exchange, calibrate coils, and verify that the system reduces power safely when a foreign object is present. It is also relevant to buyers and product managers who need to check whether a wireless charging design supports the expected safety and interoperability behaviour.

Which standards are used with prEN IEC 63758-5-4:2026?

• ISO/IEC Directives, Part 2 - Defines the wording rules behind shall, should, may, and can in the specification.
• IEC 62368-1:2018 - Provides the thermal burn injury safety context referenced by the in-power-transfer foreign-object limits.
• Qi Specification - Communications Protocol - Supplies the packet definitions and negotiation behaviour used when PTx and PRx exchange FOD-related parameters.
• Qi Specification - MPP Power Delivery - Provides the power-delivery concepts used by the FOD methods, including K estimation and equivalent inverter voltage references.
• Qi Specification - MPP Communications Protocol - Provides the communication framework used for the MPP negotiation and packet exchanges.
• Qi Specification - MPP Design Guidelines (Informative) - Supplies the power-loss split model referenced by MPLA.
• Qi Specification - Foreign Object Detection book - Provides the related Q-measurement and analysis material that the methods in this part rely on.

What does the prEN IEC 63758-5-4:2026 document contain?

The document contains measurement methods, calibration procedures, packet exchanges, compliance specifications, equations, figures, and error budgets for FOD in Qi MPP systems. It uses flow diagrams to show when to ping, when to wait for settling, and when to set or clear foreign-object flags.

Clause 3 and Clause 4 focus on Q-based detection and include theory-of-operation material, implementation guidance, and example timing behaviour. Clause 5 and Clause 6 add the MPLA and MPLA2 equations, parameter representations, ecosystem scaling, and compliance checks for transmitter and receiver behaviour.

Clause 7 contains the DPLOSS calibration workflow, linear calibration checks, fit-error checks, and the conditions that trigger fallback to lower power. Clause 8 then lists nominal coefficient values for MPLA, MPLA2, and MatedQ, which are used as reference values during design and testing.

SLOVENSKI STANDARD
01-november-2026
Specifikacija Qi - Različica 2.3 - 5-4. del: Mpp - Odkrivanje, zaznavanje tujkov (hitri
postopek)
Qi specification - Version 2.3 - Part 5-4: Mpp - Foreign object detection (Fast Track)
Ta slovenski standard je istoveten z: prEN IEC 63758-5-4:2026
ICS:
29.240.99 Druga oprema v zvezi z Other equipment related to
omrežji za prenos in power transmission and
distribucijo električne energije distribution networks
33.160.99 Druga avdio, video in Other audio, video and
avdiovizuelna oprema audiovisual equipment
35.200 Vmesniška in povezovalna Interface and interconnection
oprema equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

100/4546/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 63758-5-4 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-09-18 2026-12-11
SUPERSEDES DOCUMENTS:
IEC TC 100 : AUDIO, VIDEO AND MULTIMEDIA SYSTEMS AND EQUIPMENT
SECRETARIAT: SECRETARY:
Japan Ms Mahiru Uehara
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):
TC 106,TC 108
ASPECTS CONCERNED:
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft for
Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they
are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some Countries”
clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is the final stage for
submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Qi Specification - Version 2.3 - Part 5-4: MPP - Foreign object detection (Fast Track)

PROPOSED STABILITY DATE: 2029
NOTE FROM TC/SC OFFICERS:
As this is a fast-track process offered by WPC, the Word file is not provided.

electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

QiSpecification
MPP–ForeignObjectDetection
Version2.3
PublishDate:08December2025
DISCLAIMER
Theinformationcontainedhereinisbelievedtobeaccurateasofthedateofpublication,butisprovided“asis”andmay
containerrors.TheWirelessPowerConsortiummakesnowarranty,expressorimplied,withrespecttothisdocument
anditscontents,includinganywarrantyoftitle,ownership,merchantability,orfitnessforaparticularuseorpurpose.
NeithertheWirelessPowerConsortium,noranymemberoftheWirelessPowerConsortiumwillbeliableforerrorsin
thisdocumentorforanydamages,includingindirectorconsequential,fromuseoforrelianceontheaccuracyofthis
document.Foranyfurtherexplanationofthecontentsofthisdocument,orincaseofanyperceivedinconsistencyor
ambiguityofinterpretation,contact:[e-mail].

Contents
1. General 7
1.1 StructureoftheQi Specification 7
1.2 Scope 8
1.3 Compliance 8
1.4 References 8
1.5 Conventions 9
1.5.1 Notationofnumbers 9
1.5.2 Tolerances 9
1.5.3 Fieldsinadatapacket 9
1.5.4 Notationoftextstrings 10
1.5.5 Short-handnotationfordatapackets 10
2. ForeignObjectDetection 11
2.1 Background 11
3. Open-airQ-Test(pre-powertransferFODmethod) 12
3.1 Introduction 12
3.2 MovementTimer 13
3.3 SettlingTimer 14
3.4 Open-airQ-TestRecommendations 15
3.4.1 PTxQ-TestRecommendation1 15
3.4.2 PTxQ-TestRecommendation2 15
3.4.3 PTxQ-TestRecommendation3 15
3.4.4 PTxQ-TestRecommendation4 15
3.4.5 PTxQ-TestRecommendation5 15
3.4.6 PTxQ-TestRecommendation6 15
3.4.7 PTxQ-TestRecommendation7 15
3.4.8 PTxQ-TestRecommendation8 15
3.4.9 PTxQ-TestRecommendation9 15
3.4.10 PTxQ-TestRecommendation10 15
3.4.11 PTxQ-TestRecommendation11 16
3.5 TheoryofOperation 17
3.5.1 MeasuringQ 17
3.5.2 Qcompensationfordrift 20
3.5.3 ChoosingaQdeflectionthreshold 20
3.5.4 PotentialImplementationIssues 21
3.5.5 Summary 21
3.6 PRxmovementanddigitalping 22
4. MatedQ-DeflectionTest(pre-powertransferFODmethod) 24
4.1 Introduction 24
4.2 MatedQ-DeflectionTestSpecifications 25
4.2.1 PTxMatedQ-DeflectionTestSpec1 25

4.2.2 PTxMatedQ-DeflectionTestSpec2 25
4.2.3 PRxMatedQ-DeflectionTestSpec1 25
4.3 Recommendations 25
4.3.1 PTxMatedQ-DeflectionRecommendation1 25
4.3.2 PTxMatedQ-DeflectionRecommendation2 25
4.3.3 PTxMatedQ-DeflectionRecommendation3 25
4.3.4 PRxMatedQ-DeflectionRecommendation1 25
4.3.5 PRxMatedQ-DeflectionRecommendation2 25
4.3.6 PRxMatedQ-DeflectionRecommendation3 25
4.4 TheoryofOperation 26
4.4.1 Notation 26
4.4.2 ThresholdCalculation 26
4.4.3 EcosystemScaling 26
4.4.4 CoefficientGenerationandExtraction 27
4.4.5 DerivationofDistanceMethod 28
4.4.6 Example 29
4.4.7 MethodtoDetermineThreshold 30
5. MPPPowerLossAccounting(in-powertransferFODmethod) 32
5.1 Introduction 32
5.2 MPLASpecifications 33
5.2.1 MPLAPRxSpecifications 33
5.2.2 MPLAPTxSpecifications 35
5.2.3 ParameterRepresentations 38
5.3 MPLAEquations 39
5.4 Eco-SystemScaling 40
5.4.1 Introduction 40
5.4.2 Eco-SystemScalingDerivation 41
5.5 ProcessofExtractingLQK-DependentCoefficients 43
5.6 FOpowerestimationerrorduetoinverterhardswitching 44
5.7 FOpowerestimationerroroutside2x2cylinder 45
5.8 FODetectionThresholds 46
5.8.1 FODetectionThresholds 46
5.8.2 PFODistributionsforScenarios1and2 47
5.9 In-PowerFODAction 49
5.9.1 FODAction 49
5.10 AccessoryPowerLossRequirements 52
5.10.1 AccessoryPowerLoss 52
5.11 ErrorBudget 53
5.11.1 Introduction 53
5.11.2 MeasurementErrorAnalysis 54
5.11.3 PFOErrorBudget 57
5.11.4 Is3-sigmaSufficient? 58
5.11.5 PowerLossAccountingComplianceTesting 59

5.12 Measuringcoilcurrent 61
6. MPLAImprovementsforPowerModes(MPLA2) 62
6.1 MPLA2Equations 62
6.2 EcosystemScaling 62
6.3 MPLA2PTxSpecifications 63
6.3.1 PTxMPLA2Spec1 63
6.3.2 PTxMPLA2Spec2 63
6.3.3 PTxMPLA2Spec3 63
6.3.4 PTxMPLA2Spec4 63
6.3.5 PTxMPLA2Spec5 63
6.3.6 PTxMPLA2Spec6 64
6.3.7 PTxMPLA2Spec7 64
6.3.8 PTxMPLA2Spec8 64
6.3.9 PTxMPLA2Spec9 64
6.3.10 PTxMPLA2Spec10 64
6.3.11 PTxMPLA2Spec11 64
6.3.12 PTxMPLA2Spec12 64
6.3.13 PTxMPLA2Spec13 65
6.3.14 PTxMPLA2Spec14 65
6.3.15 PTxMPLA2Spec15 65
6.3.16 PTxMPLA2Spec16 65
6.3.17 PTxMPLA2Spec17 65
6.4 MPLA2PTxRecommendations 66
6.4.1 PTxMPLA2Recommendation1 66
6.4.2 PTxMPLA2Recommendation2 66
6.5 MPLA2PRxSpecifications 67
6.5.1 PRxMPLA2Spec1 67
6.5.2 PRxMPLA2Spec2 67
6.5.3 PRxMPLA2Spec3 67
6.5.4 PRxMPLA2Spec4 67
6.5.5 PRxMPLA2Spec5 67
6.5.6 PRxMPLA2Spec6 67
6.5.7 PRxMPLA2Spec7 67
6.5.8 PRxMPLA2Spec8 67
6.5.9 PRxMPLA2Spec9 68
6.5.10 PRxMPLA2Spec10 68
6.5.11 PRxMPLA2Spec11 68
6.5.12 PRxMPLA2Spec12 68
6.5.13 PRxMPLA2Spec13 68
7. DPLOSS(in-powertransferFODmethod) 69
7.1 DPLOSSSpecifications 70
7.1.1 PTxDPLOSSSpec1 70
7.1.2 PTxDPLOSSSpec2 70
7.1.3 PTxDPLOSSSpec3 70
7.1.4 PTxDPLOSSSpec4 70
7.1.5 PTxDPLOSSSpec5 70
7.1.6 PTxDPLOSSSpec6 70
7.1.7 PTxDPLOSSSpec7 70
7.1.8 PTxDPLOSSSpec8 70
7.1.9 PTxDPLOSSSpec9 70
7.1.10 PTxDPLOSSSpec10 70
7.1.11 PTxDPLOSSSpec11 71
7.1.12 PTxDPLOSSSpec12 71
7.1.13 PTxDPLOSSSpec13 71
7.1.14 PTxDPLOSSRecommendation1 71
7.1.15 PTxDPLOSSRecommendation2 71
7.1.16 PTxDPLOSSRecommendation3 71
7.1.17 PTxDPLOSSRecommendation4 71
7.1.18 PRxDPLOSSSpec1 71
7.1.19 PRxDPLOSSSpec2 71
7.1.20 PRxDPLOSSSpec3 71
7.1.21 PRxDPLOSSSpec4 71
7.1.22 PRxDPLOSSSpec5 72
7.1.23 PRxDPLOSSRecommendation1 72
7.1.24 PRxDPLOSSRecommendation2 72
7.1.25 PRxDPLOSSRecommendation3 72
7.1.26 PRxDPLOSSRecommendation4 72
7.2 TheoryofOperation 73
7.2.1 CalculatingPLoss_CompensatedandPLOSS 73
7.2.2 CalibrationProcedure 73
7.2.3 LinearCalibrationCheck 75
7.2.4 CheckingforFitError 75
7.2.5 EvaluatingDPLOSS 75
7.3 DPLOSSwithaSwitched-Capacitor-BasedPRxSystem 76
7.3.1 PTxrequirementtobeoutofPhaseshiftcontrolduringCalibration 76
7.3.2 DeltaPLoss(DPLOSS)ErrorBudget 77
7.3.3 PowerLossAccountingComplianceTesting 78
8. GGValueDefinitions 79
8.1 MPLAcoefficients 79
8.2 MPLA2coefficients 79
8.3 MatedQcoefficients 79
1. General
TheWirelessPowerConsortium(WPC)isaworldwideorganizationthataimstodevelopandpromoteglobalstandards
forwirelesspowertransferinvariousapplicationareas.Animportantapplicationareacomprisesflat-surfacedevices
suchasmobilephonesandchargersoperatingatpowerlevelsupto25W.
1.1 StructureoftheQi Specification
Generaldocuments
l
Introduction
l
Glossary,Acronyms,andSymbols
l
TechnicalSystemOverview
l
PowerProfiles
Systemdescriptiondocuments
l
Mechanical,Thermal,andUserInterface
l
PowerDelivery
l
CommunicationsPhysicalLayer
l
CommunicationsProtocol
l
ForeignObjectDetection
l
NFCTagProtection
l
AuthenticationProtocol
l
MPPCommunicationsProtocol
l
MPPMagneticsDesign
l
MPP PowerDelivery
l
MPP CommunicationsPhysicalLayer
l
MPP ForeignObjectDetection
l
MPP DesignGuidelines(Informative)
l
MagneticCovers
l
ActiveAlignmentSystem
l
ThermalManagementProtocol
1.2 Scope
TheQiSpecification,MPPForeignObjectDetection(thisdocument)definesmethodsforensuringthatthepowertransfer
proceedswithoutheatingmetalobjectsinthemagneticfieldofaPowerTransmitter.AlthoughthePowerTransmitter
mayoptionallyuseanyofthesemethods,someofthemrequireassistancebythePowerReceiver.
1.3 Compliance
AllprovisionsintheQiSpecificationaremandatory,unlessspecificallyindicatedasrecommended,optional,note,
example,orinformative.VerbalexpressionofprovisionsinthisSpecificationfollowtherulesprovidedinISO/IEC
Directives,Part2.
Table1-Verbalformsforexpressionsofprovisions
Provision Verbalform
requirement “shall”or“shallnot”
recommendation “should”or“shouldnot”
permission “may”or“maynot”
capability “can”or“cannot”
1.4 References
Forundatedreferences,themostrecentlypublisheddocumentapplies.ThemostrecentWPCpublicationscanbe
downloadedfromhttp://www.wirelesspowerconsortium.com.

1.5 Conventions
1.5.1 Notationofnumbers
l
Realnumbersusethedigits0to9,adecimalpoint,andoptionallyanexponentialpart.
l
Integernumbersindecimalnotationusethedigits0to9.
l
Integernumbersinhexadecimalnotationusethehexadecimaldigits0to9andAtoF,andareprefixedby"0x"
unlessexplicitlyindicatedotherwise.
l
SinglebitvaluesusethewordsZEROandONE.
1.5.2 Tolerances
Unlessindicatedotherwise,allnumericvaluesintheQiSpecificationareexactlyasspecifiedanddonothaveany
impliedtolerance.
1.5.3 Fieldsinadatapacket
Anumericvaluestoredinafieldofadatapacketusesabig-endianformat.Bitsthataremoresignificantarestoredata
lowerbyteoffsetthanbitsthatarelesssignificant.Table2andFigure1provideexamplesoftheinterpretationofsuch
fields.
Table2-Exampleoffieldsinadatapacket(table)
b b b b b b b b
7 6 5 4 3 2 1 0
B (msb)
B 16-bitNumericDataField (lsb)
B OtherField
(msb)
B 16-bitNumericDataField (lsb)
Field
Figure1-Examplesoffieldsinadatapacket

1.5.4 Notationoftextstrings
TextstringsconsistofasequenceofprintableASCIIcharacters(i.e.intherangeof0x20to0x7E)enclosedindouble
quotes(").Textstringsarestoredinfieldsofdatastructureswiththefirstcharacterofthestringatthelowestbyte
offset,andarepaddedwithASCIINUL(0x00)characterstotheendofthefieldwherenecessary.
EXAMPLE: Thetextstring“WPC”isstoredinasix-bytefieldsasthesequenceofcharacters'W','P','C',NUL,NUL,and
NUL.Thetextstring“M:4D3A”isstoredinasix-bytefieldasthesequence'M',':','4','D','3',and'A'.
1.5.5 Short-handnotationfordatapackets
Inmanyinstances,theQiSpecificationreferstoadatapacketusingthefollowingshorthandnotation:
/
Inthisnotation,referstothedatapacket'smnemonicdefinedintheQiSpecification,Communications
Protocol,andreferstoaparticularvalueinafieldofthedatapacket.Thedefinitionsofthedatapacketsin
theQiSpecification,CommunicationsProtocol,listthemeaningsofthemodifiers.
Forexample,EPT/ccreferstoanEndPowerTransferdatapackethavingitsEndPowerTransfercodefieldsetto0x01.

2. ForeignObjectDetection
2.1 Background
Tosupporthigherpowerupto25W,MPP usesamulti-stepapproachtoforeignobjectdetection(FOD).Themost
commonsituationinwhichanFOarrivesbetweenthePTxandPRxisifitisplacedonthePTxfirst(sequential
placementofFO).ComparedwiththecasewheretheFOisplacedsimultaneouslywiththePRx,theuserismoreeasily
exposedtoanover-heatedFOifpowerdeliverystarts.WhentheFOisplacedonthePTxpriortoplacementofthePRx
itcaneasilybedetectedusinganOpen-airQ-Test(pre-powertransferFODmethod)whichisexecutedduringthe
analoguepingphase.Becausetheopen-airQtestissoaccurateandisnotaffectedbythepresenceofaPRx,itcanbe
usedtoguaranteethereisnoFOwhichwillover-heatevenatmaximumpowerdelivery.
InthecasethattheFOarriveswiththeplacementofthePRx,thePTxcandetectthepresenceofanFOusingMatedQ-
DeflectionTest(seeSection4,MatedQ-DeflectionTest(pre-powertransferFODmethod)),whichleveragesthesame
measurementscollectedduringtheOpen-airQ-Test.MatedQ-DeflectionforMPPassuresthedetectionofanFOplaced
withaPRxduetothetightlydefinedmagneticstatespace.
InthecasetheFOisplacedbetweenaPTxandPRxduringpowertransfer,therearetwomethodstodetectanFO.The
firstisMPPPowerLossAccounting(in-powertransferFODmethod) whichisusedforFOdetectionupto15W.The
secondisDeltaP_loss(∆Ploss)whichisusedtoextendFOdetectionupto25W.Accuratelydetectingthepresenceofan
FOduringpowertransferisachallengingtask.ItmaybethecasethatFOdetectionwhichiscompletelydependenton
in-powertransferFODwillhavetolimitthepowertransfertosomethinglowerthanmaximum.
Table3summarizesanypowerlimitationsthatoccurdependingontheresultoftheopen-airQtest.
Table3-Powerlimitationsdependingonopen-airQtestresults.
Open-AirQTest Result
Notimplemented
Limitmaximumpowerdeliverytothelevelsupportedby
PRxplacedonPTxpriortopowerbeing
Section5,MPPPowerLossAccounting(in-powertransferFOD
appliedtoPTx
method) aloneandsettheSection5.8,FODetectionThresholds
FOarriveswithPRx
totheIEC62368compliancelevel.
FOdetectedonPTX
NoFOdetected Allowmaximumpowerdelivery.

3. Open-airQ-Test(pre-powertransferFODmethod)
3.1 Introduction
Thissectionintroducesapre-powerforeignobjectdetection(FOD)methodthatisusefulfordetectingforeignobjects
placedonthePTxmatpriortothearrivalofthePRx.
Thisopen-airQtestisnotasubstituteforin-powertransferFOD,noramated-Qmethod.Theopen-airQtestwillnot
detectFOswhicharriveonthePTxsimultaneouslywiththePRx,oriftheFOisinsertedinthepowertransmitter’sfield
afterthePRxhasarrived.
Thebasicfunctionalityoftheadditionalmethoddescribedinthisdocumentconsistsincomparingtheresponsetoan
analoguepingwhenPTxisrunning,withthestored-in-unitresponsetoanaloguepingwhenPTxisinfreeair.
Duringthestart-upphase,thePTxusesanaloguepingtomeasureadeflectiontoQdefinedas:
Equation:1
Figure2- DetectionCapabilityV.S.ThermalRequirements.
where isthecalibratedvalueforopen-airQmeasuredatproductionandQismeasuredbyanaloguepingor
calculatedfromadirectimpedancemeasurementatrun-time.Notethat ifthereisnoFOpresent,butit’snot
exactlyzerobecauseofeffectssuchastemperaturedriftasdiscussedlaterinthisdocument.Componentagingwillalso
cause whenPTxisoperatinginfreeair.
Whenanobjectisplacedonthemat,theQwillbedeflectedbysomeamount.If islargeenough,anobjectcanbe
inferred.AresponsefromdigitalpingcanthenbeusedtodistinguishbetweenwhetheranFOorapowerreceiverwas
placedonthemat.AbasicflowisprovidedinFigure3.

Ifopen-airtestisnotimplemented,thePTxinternalopen-airFOflagshouldbesetsothatthein-powerFODmethod
knowsthattheopen-airFOtestdidnotdetectthematclearofFOs.ThepowercontractwithPRxshouldbenegotiated
tothemaximumpowerthatin-powerFODcanguaranteewithnoFOover-heating.
Figure3-Simplifiedflowdiagramforopen-airQtest.
3.2 MovementTimer
IntheQ-testflowdiagram,amovementtimerissetonceaQdeflectionisdetected.Whilethistimerisrunning,analogue
pingscontinueuntileither(a)aresponsetothedigitalpingoccursindicatingthepresenceofareceiveror(b)the
movementtimerexpires.Thepurposeofthemovementtimeristopreventareceiverplacedfarenoughoff-centretobe
falselydetectedasanFOwhiletheuserisslidingthereceiverintoplace.FalsedetectionofFOcouldhappeninsucha
scenariobecausetheopen-airQ-deflectionisquitesensitive,moresothandigitalping.

Thedurationofthemovementtimershouldbe1-2s.Becauseofthemagnetattach,thereceiverwillsnapintoplace
veryquickly.MoreinformationaboutthemovementtimeisprovidedinSection3.5.4.2,PRxmisplacedthenreplaced.
3.3 SettlingTimer
BecausetheKEstimation(seetheMPPPowerDeliverybook)occursaftersuccessfuldigitalping,itisimportantfor
digitalpingstocommenceonlyaftertheQdeflectionhassettled.TheQdeflectionbeingsettledindicatesthatthePRxis
nowinpositionandnolongermoving.MoreinformationisprovidedinSection3.6,PRxmovementanddigitalping.

3.4 Open-airQ-TestRecommendations
3.4.1 PTxQ-TestRecommendation1
Ifimplemented,theopen-airQtestshoulddetectthepresenceofaForeignObjectwithintheareadefinedbythecritical
radiusbeforepowertransferbegins.
3.4.2 PTxQ-TestRecommendation2
Ifimplemented,theopen-airQtestshouldbeperformedperiodicallyduringPTxstandbywithamaximumperiodof1
Qtest/s.
3.4.3 PTxQ-TestRecommendation3
Ifimplemented,theQ-factorandthenaturalfrequencyoftheLCtankofthePTxinfreeairshouldbeknowntoPTxto
calculatetheQdeflectionwithopen-airQtest.
3.4.4 PTxQ-TestRecommendation4
Ifimplemented,PTxshouldtrytoinitiatecommunication(viadigitalping)whenopen-airQ-deflection( )ishigher
thanfreeairthreshold .
3.4.5 PTxQ-TestRecommendation5
Ifimplemented,aFOflagshouldbesetifcommunicationfailsafterdigitalpingissent.
3.4.6 PTxQ-TestRecommendation6
Ifimplemented,aFOflagshouldbesetiftheopen-airQtestisnotperformed.
3.4.7 PTxQ-TestRecommendation7
Ifimplemented,aFOflagshouldbesetifanFOwithinthecriticalradiusisdetected.
3.4.8 PTxQ-TestRecommendation8
Ifimplemented,aFOflagshouldbesetifPTxhasnotmeasuredopen-airQ-deflection( )belowfreeairthreshold(
)priortoreceivingthedigitalpingresponse.
3.4.9 PTxQ-TestRecommendation9
Ifimplemented,aFOflagshouldbeclearedifandonlyifPTxhasmeasuredopen-airQ-deflection( )belowfreeair
threshold(  ).
3.4.10 PTxQ-TestRecommendation10
IfimplementedandtheFOflagisset,themaximumpowercapabilityshouldbesetbasedonFODcapabilityofthein-
powerFODmethodtopreventtheFOfromheatingupbeyondthetemperaturelimitassociatedwiththatobjectand
placementsequence.
3.4.11 PTxQ-TestRecommendation11
Ifimplemented,themaximum (totalresistanceinfreeair)oftheMPPPTxshouldbelimitedto:
GiventheresistancevariationcausedbytheFO( )andadesired .

3.5 TheoryofOperation
3.5.1 MeasuringQ
Inthisapproach,apulseofenergyisinjectedintothecoilandthedecayoftheringingresponseismeasured.Qisthen
estimatedfromthedecayenvelope.SeeEstimateQfromthedecayoftheringingresponsetoapulsefromAnnexB,
ForeignObjectDetectionbook.
Figure4-Implementationofhowtomeasureringresponse.
Figure4showsapossibleimplementationbydrivingtheFETsoftheinverter.Thedifferentphasescanbedescribedas:
1. t-startup
Duringthistime,theinputvoltageoftheinverterisallowedtoreachtherequirednominalvoltagefortheping.
2. t-discharge
Thepurposeofthisstageistodischargetheresonantcapacitorandtoestablishtheinitialconditionsfortheping
(i.e.VCtx(0)=0,iLtx(0)=0).Thisshouldbedonebyshortingtheresonanttankviathebottomswitchesofthe
invertingbridge(e.g.Q3andQ4).
3. t-ping
Thisistheenergyinjectionstage.Duringthisstage,theDCsourceisconnectedacrossthePTxresonanttankfor
t-pingtime.ThisshouldbedonebyturningoffQ3,turningonQ1,andleavingQ4onasshowninFigure4.
4. t-response
Afterenergyisbeinginjectedintothetankduringthepingstage,thetankshouldbeshortedviathelowside
switchestoallowforfreeoscillationoftheresonanttank.ThisshouldbedonebyturningoffQ1andturningon
Q3.Thenaturalresponseofthetank(e.g.thevoltageacrossthePTxtuningcap)isthensampledandprocessed.
EstimatingQrequiresaccuratesamplingofthewaveformpeakstoobtainitsenvelope.ToeliminatetheimpactoftheDC
offsetfromthedecayestimatetheenvelopeamplitudecanbemeasuredasthepeak-to-valleydifference.Pleasereferto
AnnexB.2,ForeignObjectDetectionbook.

3.5.1.1 NoteonPTxwithmultipleresonantcapacitors
Thestateofchargeofthetransmitterresonantcapacitors,CTx,affectstheMatedQresponse.Toachieveaconsistent
MatedQresponse,theCTxcapacitorsneedtobeprecharged.Thiscanbeachievedwithbiasping.Thebiasping
energizesAC2node.Afterthepre-chargephase,anotherdischargephaseisrequiredtodischargethecapacitortobe
usedduringtheMatedQping.TheinvertertimingsequenceisdescribedinFigure5.
H
Q1 Q2 Q1
Rtx Ltx
H
AC1
Q2
H H
Q3
Ctx
H H
Q4
AC2
Q3 Q4
Icap_bank
t-startup t-bias t-ping
t-discharge1 t-discharge2 t-response
Figure5-biaspingconfiguration.
Thebiaspingshouldbesentwhilethesystemisinfreeairasdeterminedbytheanalogueping.Onceitisdeterminedan
objectispresent,biaspingshallberemovedduringtheQdeflectionsettlingperiod(SeeSection3.6,PRxmovementand
digitalping)becauseitimpactstheMatedQresponse.
Ingeneral,abiaspingshallbesentpriortoenteringsettlingphaseandasettlingphaseisrequiredforMatedQ
calculation.Exampleswheresettlingisrequiredinclude:
1. AreconnecteventafteraCOMMsdisconnectbeforeproceedingtotheQdeflectionsettlingperiod.
2. AdigitalpingfailstoestablishcommunicationswithaPRx.
3. APRxrequestsCloakwithreason"FODPause",thePTxshallscheduleabiaspingbeforeenteringsettlingphase.
Figure6,Figure7,andFigure8showtimingdiagramsforthescenariosdescribedabove.
Free Air Object Present
Bias Ping
Q settled
Digital Ping
Qdeflection
settling
Figure6-AreconnecteventafteraCOMMsdisconnectbeforeproceedingtotheQdeflectionsettlingperiod

Disconnect
Disconnect
Timeout
Power Signal
Bias Ping
Q settled
Analogue Ping
Digital Ping
Qdeflection
settling
Figure7-AdigitalpingfailstoestablishcommunicationswithaPRx
FOD Cloak
Cloak Exit
Reason
Power Signal
Bias Ping
Q settled
Analogue Ping
Qdeflection
settling
Figure8-APRxrequestsCloakwithreason"FODPause",thePTxshallscheduleabiaspingbeforeentering
settlingphase
TheflowchartinFigure9describestherelationshipbetweenbiasandanaloguepings.
Send Bias Ping
Send Analogue Ping
Y
Free Air?
N
Send Analogue Ping
N
Qdeflection
Settled?
Y
Send Digital Ping
Figure9-Relationshipbetweenbiaspingsandanaloguepings
ItiscriticalforthePRxtousethesameHWconfigurationduringallMatedQmeasurements.AdifferenceinCRx
selectionoradditionalloadontherectifierwillimpactMatedQ.ThisisespeciallyimportantduringFODCloak.AfterFOD
cloak,MatedQismeasuredandcomparedtoitsvaluebeforedigitalpingtocheckforthepresenceofanFO.
3.5.1.2 ImpactofFOorPRxonOpen-AirQ-deflection
PleaserefertoAnnexB3,ForeignObjectDetectionbook.

3.5.2 Qcompensationfordrift
ThissectionprovidessomepossibilitiesforimprovingtheQdeflectionmeasurementwhichmayormaynotbeneeded
forsomeimplementations.TheQdeflectionin isintendedtocomparetherun-timemeasurementofQagainstthe
productioncalibratedmeasurementofQ.Duringrun-time,effectsbesidesthepresenceofanFOsuchastemperature
andfrequencydriftcanresultinQdeflection.Compensatingfortheseeffectsimprovesthereliabilityoftheopen-airQ
test.
3.5.2.1 AccentuatingQdeflectionduetofrequencydriftcausedbyFO
PleaserefertoAnnexB4,ForeignObjectDetectionbook.
3.5.2.2 TemperatureCompensation
PleaserefertoAnnexB6,ForeignObjectDetectionbook.
3.5.2.3 SeparatingDCandACresistance
ManydrifteffectsinthemeasurementofQoccurtotheDCportionoftheresistance(frequencyindependent)which,
itself,isnotaffectedbythepresenceofanFO.Frequencyindependent“DCresistances”includeresistancesfromthePCB
tracesandinverterFETresistances.IftheDCresistanceisseparatedfromtheoverallresistance,theDCresistancecan
becalibratedatproductionandremovetheimpactofDCresistancedrift.Specifically,let:
Equation:2
wherewe’veindicatedthatR (T)issensitivetotemperaturewhileR (T,ω)issensitivetotemperatureand
DC coil,AC
frequency.
UsingEquation:2,Qcanbewrittenas:
Equation:3
Thetotalresistance,R,canalsobedeterminedbytheanaloguepingringingresponse:
Equation:4
Equation:5
Equation:6
IftheDCresistanceismeasured,itsvalue,R ,canbestoredatproductionandthencomputeQatrun-timeas:
DC,0
Equation:7
ThiseffectivelyeliminatesDCdriftfromtheQmeasurementatthecostofadditionalmeasurementerrorofthe
resistances.
Finally,replace with:
Equation:8
ToachieveaQdeflectionof10%,thePTxACresistanceshouldbenomorethan~216mΩ.IfthePTxcanmeasureQ
moreaccurately,itcanaffordtohaveahigherACresistance.
3.5.3 ChoosingaQdeflectionthreshold
PleaserefertoAnnexB5,ForeignObjectDetectionbook.

3.5.4 PotentialImplementationIssues
3.5.4.1 Proximitytometalobjects
PleaserefertoAnnexB.7,ForeignObjectDetectionbook.
3.5.4.2 PRxmisplacedthenreplaced
IncaseofPRxmisplacement(e.g.placingthePRxonPTxthenslidingittoacorrectposition)anFOflagcouldbeset,
consequently,PTxcouldinhibitpowertransferorstartpowertransferatareducepowerratewhenPRxisthenplaced
onacorrectposition.
Tomitigatethisissue,apossibleSection3.2,MovementTimercouldbeintroducedasshowninFigure3.Themitigation
consistsindelayingtheFOflaginanattempttoestablishcommunicationbeforethemovementtimerexpiresasshown
inFigure10.
Figure10-PRxreplacedbeforethemovementtimerexpirestopreventfalseFOflag.
3.5.5 Summary
Theopen-airQtestisusedtocalculatetheopen-airQ-deflection.
Open-airQ-deflectionmeasuresthevariationoftheQ-factorduringruntimefromitsvaluewheninfreeair(unmated
andwithnoForeignObjects):
l
ΔQisopen-airQ-deflection
l
QistheQ-factorcalculatedin-fieldduringruntimeoperation,thisparametercouldbecompensatedforR drift
AC
duetoagingand/ortemperature
l
Q istheQ-factorinfreeairanditcouldbestoredintheunitduringproduction
Atthecriticalradius,theopen-airQ-deflectionisdefinedasfollows(assumingΔL =0):
FO
l
R istotalresistanceofthecoilandeverythingelseinthepathofQmeasurement(e.g.FETswitches,PCBtraces,
AC
capESR).
l
ΔR isthevariationofR duetothepresenceofaFOatthecriticalradius
FO AC
l
ΔL isthevariationofL (inductanceinfreeair)duetothepresenceofaFOatthecriticalradius
FO 0
Theopen-airQ-deflectionthresholdshouldhaveenoughmargintoaccountformeasurementerrorandcomponent
aging:
l
ΔQ istheopen-airQ-deflectionthreshold
th
l
ΔQ istheopen-airQ-deflectionvaluewhenaForeignObjectisplacedatthecriticalradius
critical
l
d istheopen-airQ-deflectiondriftcausebyaging
aging
l
e istheopen-airQ-deflectioninaccuracyintroducedbythealgorithmusedtocalculatedQ-factor
error
Theopen-airQ-deflectionthresholdcouldbeaffectedbytheproximitytometalobject(e.g.PTxplacedonametaltable).
3.6 PRxmovementanddigitalping
IthasbeenshownhowtochooseaQdeflectionthresholdbasedonΔR causedbythepresenceofaFO.Thisimplies
AC
thatwhenPTxdetects > adigitalpingwillbesenttotrytoestablishcommunications.PRxcouldcausea
Qdeflectionhigherthanthethresholdswhileit'sapproachingPTx,leadingtoapossiblefailuretorespondtodigitalping
fromPTxorpoorcouplingestimation.FailingtorespondtodigitalpingleadstosettingtheFOflaghencepossible
powertransferlimitation.
Toavoidthisissue,itispossibletointroduceaQdeflectionsettlingperiodduringwhichthePTxwillwaituntilthe
computedQdeflectionissettle(PRxnotmoving)tosendadigitalpingandtrytoestablishcommunications.
Thefollowingscenariodescribesapossibleimplementationofthesettlingperiod:
1. PTxisinstand-bymode,calculating periodically(e.g.every100ms)
2. PRxisapproachingPTxcausing > whilestillmoving
3. PTxwillenterasettlingperiodassoonas >
4. PTxwillkeepcalculating (thesamplingratecouldbeincreasedtoimprovetheresolution)
5. isconsideredsettledonlyifithasnotvariedbeyond± %(e.g.1%)foratleastt (e.g.200ms),
settle
indicatingthatthePRxisstationary
6. ThissettlingcriterionwillensurethatwhenaPRxisplacedonaPTxandadigitalpingissent, willbe
measuredaccurately.
and defineaminimumPRxplacementvelocity.Thisisrequiredtoavoidsendingadigitalping
prematurelythatcouldaffectthecouplingestimation.
Tocalculatetheminimumplacementvelocity,thedesignershouldconsiderthesmallestvariationof overthearea
ofinterestofthePTx.
Forinstance,let:
variationof overx-axisofthePTx
Theminimumrequiredvelocitytoavoidprematuresettlingis:
pleasenotethat needstobeassmallaspossibleandit'slimitedbynoise,algorithminaccuracyandpossible
interactionswithPRx.
Apossiblescenario:
=1.0406mm/%
=1%
=187.5ms
v =5.55mm/s
min
Figure11showsanexampleofwhatopen-airQ-deflectionlookslikewhenPRxisapproachingPTx.During(1)theopen-
airQ-deflectionis0%andat(2)theopen-airQ-deflectionhasexceededthethreshold.Thesamplingratecouldbe
increasedonce > toimprovetheresolution.At(3)theopen-airQ-deflectionhasnotchangedforthe
minimumrequiredtimethereforeadigitalpingcanbesentandpowertransfercanbegin.
Figure11-Exampleofq-deflectionprofilewhenPRxisapproachingPTx.

4. MatedQ-DeflectionTest(pre-powertransferFODmethod)
4.1 Introduction
MatedQ-DeflectiontakesadvantageofthesamemeasurementmethodsasOpen-airQ-Testmeasurement.MatedQwill
usethelastmeasurement(s)fromthesettledOpen-airQvalue.Assuch,thissectionwillassumeknowledgeofAnnexB4,
ForeignObjectDetectionbooktomeasurethequalityfactorofthepowertransmittersresonantcircuit.
PreviousconceptionsofMatedQstruggledduetoalargemagneticstatespace.WithMPP,themagneticstatespaceis
tightlydefined,whichallowsforpredictableandlinearbehaviourthatcanbecompensatedwithcrosstermsexchanged
atstartup.MatedQ-deflectioncurrentlyisabletodetectFOsatpositionsontheinterfacesurfacewherethereisariskof
heatingabovetemperaturelimitswithoutfalselydetectinganFOwhennoneispresent.
and aremeasuredandcalculatedidenticallyasdescribedin“AnnexB.2:Measuringthequalityfactor”
intheForeignObjectDetectionbook,withthefollowingadditiontoadjustforMatedQfactorycalibration.
Equation:9Deflection withcalibration
FrequencydeflectionissimilarlycalculatedandadjustedforwithMatedffactorycalibration.
Equation:10f deflectionwithcalibration
These and measurementsaretakenwhenthelastOpen-airQ-measurementfinishedduringOpen-air
Qsettling.
Inordertoimprovedetectionmargins,per-unitcalibrationisperformedforeachPTxdeviceduringmanufacturing.This
involvescalibratingeachunitagainstareferencePRxcoil,suchastheTPRcoil,atafixedpositionofr=0mmandz=2
mm.
Thecalibrationresultsarerepresentedby and ,whichcorrespondtothematedmeasurementsofQ
andfbetweenthePTxandreferencePRxcoil,respectively(seeFigure12).

4.2 MatedQ-DeflectionTestSpecifications
4.2.1 PTxMatedQ-DeflectionTestSpec1
ThePTxshallsettheFO fieldto2intheMATEDQ_RESdatapacketwhenaforeignobjectisplacedatapositionthat
wouldleadtooverheating.
4.2.2 PTxMatedQ-DeflectionTestSpec2
PTxshallnotenterDeltaPlosscalibrationifaForeignObject(FO)isdetected.
4.2.3 PRxMatedQ-DeflectionTestSpec1
PRxshallsendvalidparametersintheMATEDQ_COEFFdatapacket(header0xA8)tothePTxduringboththe128kHz
and360kHzNegotiationPhases.
4.3 Recommendations
4.3.1 PTxMatedQ-DeflectionRecommendation1
ThePTxshouldcalculateusingEquation:9
4.3.2 PTxMatedQ-DeflectionRecommendation2
ThePTxshouldcalculateusingEquation:10
4.3.3 PTxMatedQ-DeflectionRecommendation3
EachPTxshouldmeasure and usingtheTPR#MPP4coilatthe(0,2)position.
4.3.4 PRxMatedQ-DeflectionRecommendation1
PRxMatedQ-DeflectionRecommendation1isdeprecated.
4.3.5 PRxMatedQ-DeflectionRecommendation2
PRxshouldcalculateecosystemscalingparametersasdefinedinSection4.4.3,EcosystemScaling.
4.3.6 PRxMatedQ-DeflectionRecommendation3
ThePRxshouldretrievetheMATEDQ_RESdatapacketduringtheNegotiation PhasebysendingGET[MATEDQ].

4.4 TheoryofOperation
4.4.1 Notation
Inthefollowingsections,thesubscriptofvariablesandcoefficientsdescribeswhichdevicesarematedtogether.The
firstletterinthesubscriptdenotesthetypeoftransmitter,thesecondthetypeofreceiver:
Symbol Description
ReferenceUnit(TPT/TPR)
ThenewlydesignedPTx–onlyvalidinthefirstsubscriptposition
ThenewlydesignedPRx–onlyvalidinthesecondsubscriptposition
Forexample, referstoavariableorconstantZthatisassociatedwiththeTPTandTPRpair.Likewise, referstoa
variableorconstantthatisaPTxandTPRpair,andsoon.
Inthissection,TPTandTPRareusedtorepresentthereferencetransmitterandreferencereceiverperQi2.0
specification.ThetermPTx,andPRxareusedtorepresenttheproductunderdevelopment.
4.4.2 ThresholdCalculation
ThePTxwillcalculatethelinearthresholdatruntime,basedonthefollowingequation.
Equation:11ThresholdCalculationwithcrossterms
4.4.3 EcosystemScaling
ForPRxdevices,crosstermswhichissharedwiththePTxatrun-timeisneeded.Theyaregeneratedasfollows:
Equation:12PRxCrossTerm
Equation:13PRxCrossTerm
Equation:14PRxCrossTerm
PTxdeviceswillneedtostoretheir coefficientswhilePRxdeviceswillneedtostoretheir cross-terms.
DuringruntimethePTxwillcalculatethethresholdbasedonEquation:11.

4.4.4 CoefficientGenerationandExtraction
DistanceMethodisanimplementationofMatedQalgorithm.ItdetectsFObycheckingthedistanceofmeasured
observablestotheobservableswhennoFOispresent.Thethresholdextractionprocessisbasedonthedistancetothe
linearfittedlineofPRx-onlymeasurements.Thelinearfitlineisthenshifteduptogeneratethedecisionboundary.
TheobservableswithoutFOpresencearenotknownforanygenericPTx-PRxinthefield.Thereforeecosystemscalingis
requiredtopredictthesevalues.Toachievethescaling,theTPTandTPRaredefinedasareference,andallgenericPTx
orPRxhastobepairedwiththereferencecounterparttoextractcoefficients.
Figure12-DistancetoPRxclusterthresholdmethod

4.4.5 DerivationofDistanceMethod
ThefollowingderivationassumesthegenericTxiscalledPTx,andgenericRxiscalledPRx.Also,TPT#MPP4isdefined
asthereferenceTx,calledTPT,andtheTPR#MPP4asthereferenceRx,calledTPR.Itisclaimedthattheobservablesfor
PTx-PRxpaircanbepredictedbytheobservablesofTPT/TPR,PTx-TPRandTPT-PRxpairs.
4.4.5.1 NecessaryData
BelowisalistofnecessarydatatoenabletheDistanceMethod:
1. EcosystemscalingcoefficientsforTPR-TPTpair
2. ForeachPTxorPRx,anominalunittopairwitheitherTPR#MPP4orTPT#MPP4.TakeQandfmeasurementsat
thefollowingpositions:(0,0),(1,0),(2,0),(0,2),(1,2),(2,2),(0,3),(1,3),and(2,3).
Withtheabovedata,thedetailedDistanceMethodisdescribedbelow:
Inthefollowingdiscussion,theobservablesaredefinedas and .
Equation:15
Thedeflectionofinputimpedanceoftheresonantpathcanalsobecalculatedas:
Equation:16
Thedeflectionofinputimpedanceoftheresonantpathcanalsobecalculatedas:
Equation:17
ForthegoldenTPT-TPRpair, atdifferentpositionsaremeasuredandfittedwithaline:
Equation:18
FortheTPT-PRxpair, atdifferentpositionsaremeasuredandfittedwithaline:
Equation:19
ForaPTx-TPRpair, atdifferentpositionsaremeasuredandfittedwithaline:
Equation:20
ForaPTx-PRxpairthatmeetinthefield, atdifferentpositionsarethenpredictedbyscaling:
Equation:21
where
and aregivenby:
Equation:22
Equation:23
ThePTxwillstore and
ThePRxwillstore and asdefinedinSection4.4.3,EcosystemScaling.
WhenthePTxandPRxmeetsinthefield,thePRxwillsenditscoefficientstothePTxduringnegotiation.
Afterthescaling,PTxcancomparetheactualmeasured and tothepredicted and .
Ifthedifferenceisgreaterthanthethreshold∆d,theFOflagisset.Thiscanbeexpressedbythefollowingequation:
Equation:24
Thedistancethreshold∆dshouldbeselectedsothatthereisnofalserejectionevenwiththetoleranceofmatedsystem,
phonecase,andmeasurementerror.Ontheotherhand,themaximumdetectionradiusisalsolimitedby∆d.Ifthe
detectionradiusisgreaterthanFOheatingcriticalradius,thenthemethodisconsideredsuccessful.Otherwise,
compromiseisrequiredbetweenpowercapabilityandsafety.
4.4.6 Example
Inthefollowingexample2xPTxand2xPRxarepaired,andtheirobservablesf_defandR_defareplottedwith
correspondinglinearfitinFigure13.ThescaledlineforPTxanPRxisalsoplottedinthebottomrightsubplot.The
distanceofthescalinglineandlinearfitlineistheecosystemscalingerror.
InFigure14,theobservableswithFOandphonecaseareaddedwiththethreshold.

Figure13-LinearfittinglinesforthetwoPTxandPRxpairs.
Figure14- ObservableswithFOandphonecaseareaddedwiththethreshold
4.4.7 MethodtoDetermineThreshold
ThefollowingstepscanbeusedbymanufacturerstoenabletheDistanceMethodandobtaintheThreshold.
1. CollectallnominaldataasdescribedinSection4.4.5.1,NecessaryData
2. Definetheworstcase1standarddeviation and .Additionalmargincanbeadded(example20%).These
valuesarefixedanddonotchangewithproduct.
3. ForPTx,thenominaldatapointswhenpairedwithTPRwillbelinearlyfitted(basedonLMSerror)toget
Equation:20.Themaximum distanceofthedatapointstothelinewillberecordedinPTxfirmwareas .
4. SimilarlyforPRx,thenominaldatapointswhenpairedwithTPTwillbelinearlyfittedtogetEquation:19.
Additionally,PRxwillcompareitsmaximum tothemaximum ofGGpair,andstoreitas .

5. WhenPTxandPRxmeetsinthefield,PRxwillsend and toPTxtoenablePTxtocalculatethescaledRx-
OnlylineforPTx-PRxpair.Additionally,PRxwillalsosendits toPTx.
6. PTxwilltakemax( , ),multiplyitbyapercentilemarginM,addaoffsetmarginEforRx-Onlylinescaling
error,andaddNtimesthestandarddeviationtoobtainthethreshold.ThethresholdshiftsthePTx-PRxscaled
PRx-Onlylineupasthefinaldecisionboundary, .
ThesystemmodelusesthefollowingvaluesforM,N,E,and :
l =0.2
l
=5
l
=0.0695
l
=0.028422
TheabovestepsarealsovisualisedinFigure15.
Figure15-Stepstodeterminethreshold

5. MPPPowerLossAccounting(in-powertransferFODmethod)
5.1 Introduction
Qiv1.1introducedpowerlossaccountingforin-powertransferforeignobjectdetection.Modificationsareintroduced
heretoextendpowerlossaccountingto15Wpowerdeliveryandbeyond,withouttheneedforrun-timere-calibration.
Thisenhancedapproachwillbereferredtoas"MPPPowerLossAccounting"(MPLA).
TheapproachofferedforMPLAisbasedonthefollowing:
l
MPLAisdesignedtoensureadequateaccuracysothat15Wcanbedeliveredinther=[0,2mm],z=[0,2mm](the
“2x2cylinder”,seetheGlossarybook)state-spacewithoutover-heatinganFOinordertomeettherequirements
ofIEC62368-1:2018sectiononthermalburninjuryrequirementsforwirelesspowertransmitters.
l
Thelosserrorisdesignedtoincrease(oratleastbenon-negative)asPRxpositiondisplacementincreasesfrom
thecoil’scentre.Inthisway,displacementsoutsidethe2x2cylinder,MPLAwillbebiasedtowardsfalseFO
detectionandpowerthrottlingversusmissedFOdetectionwhichwouldallowFOheatingtoexceedtemperature
limits.
(i)
l
Coilandfriendlymetallosses(seeFigure17),stronglydependentonmatedcouplingproperties(LQK ),are
separatedfromcircuitlossesoutsidethemagneticcircuit.
l
Friendlymetallossesareaccountedseparatelyfromcoillossesusingthepowerlosssplitmodeldetailedinthe
MPP DesignGuidelines(Informative)book.
l
Thelosserroriscomputedforareferencedesignpair(TPT#MPP1-TPR#MPP1)usingequationsandcoefficients
accountingforthecoilandfriendlymetalwhichareprovidedinthischapter.
l
ThereferencedesignunitsrepresentexemplaryMPPdesigns
l
PerformanceoftheerrorbetweenarbitrarymatedPTxtoPRxdesignsisensuredbyexchangingeco-
systemscalingparametersduringthenegotiationstagepriortopowerdeliveryandby(a)ensuringthat
thereferencedesignsprovideadequateperformancewhenmatedtoeachotherand(b)bychoosingthe
eco-systemscalingcoefficientstotranslatethematedPTxtoPRxinductiveproperties(LQK)totheLQKof
thereferencedesigns.
l
MPLAerrorcomplianceisevaluatedforthePTxorPRxcoupledtothehigh-accuracytesttoolswhichare
closelymatchedtotheMPPreferencedesigns.
l
ThebasicpoweraccountingapproachinBPPbiasesthePRxlossestimatetoalwaysover-estimatetheloss(Test
#57:DeltaPrerrorfrom-0to+350mW).ThisbiasisunknowntothePTxbutthePTxneedstocompensateforit
initspowerlosscalculation.InMPLA,boththePTxandPRxshouldhaveazero-meanpowerestimatessothat
computed iszero-meanwithinthe2x2cylinder.
l
Powercontractre-negotiationisprovidedtoallowpowertobereducedinthepresenceofanFOtopreventover-
heating(“besteffortcharging”).
(i)
LQKreferstothekeyelectricalobservablesofthematedinductivecoils.Thefirstletterrepresentstheinductive
parametersofthematedinductivecoils( and ).Thesecondletterrepresentsthequalityfactorofthecoil( and
).Thelastletterstandsforthecouplingfactorbetweenthecoils,whichincludestheinductivecoupling andthe
resistivecoupling .
5.2 MPLASpecifications
5.2.1 MPLAPRxSpecifications
ThesearetheMPLAspecificationsforPRx.ThepFOlimitsinPRxspecs5-6arederivedfromanerroranalysisprovided
inSection5.2.1,MPLAPRxSpecifications.
5.2.1.1 PRxMPLASpec1
DuringtheNegotiationphase,PRxshallsendparameters , ,and  toPTx.SeeTable5.
5.2.1.2 PRxMPLASpec2
DuringtheNegotiationphase,PRxshallrequestparameter  fromPTx.SeeTable5.
5.2.1.3 PRxMPLASpec3
PRxshallnegotiate and accordingtoQiSpecification,CommunicationsProtocolbook,andsetWindowsize=
[01000]( =32ms)andWindowoffset=[100]( T=16ms).
5.2.1.4 PRxMPLASpec4
PRxshallmeasureits andcalculateitsreceivedpower( )andsendthemtothePTxinthePLApacket(0x58).
5.2.1.5 PRxMPLASpec6
WithnoFOpresent,forallPRxpositionswithinthe2x2cylinder,when ≤10W,thecomputed ofPRxmatedto
theTPT#MPP1shallbewithintherange[-155mW,+155mW].
NOTE:thesevaluesaredeterminedfromtheSection5.11.3,PFOErrorBudget.
5.2.1.6 PRxMPLASpec7
WithnoFOpresent,forallPRxpositionswithinthe2x2cylinder,when >10Wuptothemaximumdeclaredpower,
thecomputed ofPRxmatedtotheTPT#MPP1shallbewithintherange[-240mW,+240mW].
NOTE:thesevaluesaredeterminedfromtheSection5.11.3,PFOErrorBudget.
5.2.1.7 PRxMPLASpec8
Outsideofthe2x2cylinder,thecomputed shallbepositive.
5.2.1.8 PRxMPLASpec9
PRxMPLASpec9isdeprecated.
5.2.1.9 PRxMPLASpec10
WhenthePRxisrampingitsloadabove7.5W,afterreceivingan"ACK"responsetoaPLApacket,itshalllimititsload
increasestostepsof1Worless.
5.2.1.10 PRxMPLASpec11
Uponreceiving“NAK”asaresponsetoaPLApacket,If islowerthanthetargetlevelminus1.5V,PRxshallreduce
itsloadtobring within-1.5V/+0.5Vofthetarget.

5.2.1.11 PRxMPLASpec12
Uponreceiving“NAK”asaresponsetoaPLApacket,PRxshallnotrampupitsloadpower(evenif  islessthanthe
targetpower).
5.2.1.12 PRxMPLASpec13
Uponreceiving“NAK”asaresponsetoaPLApacket,PRxshallcomputeandsendanewPLApacketevery250ms-300
ms.
5.2.1.13 PRxMPLASpec14
shallhaveavalueof1.0.
NOTE:TheMPLAimplementationforMPPensuresthatMPLASpecparametervaluescanbeempiricallydeterminedandmeasured.
Toenablethis,MPLAusesthebarecoppercoilACresistanceofthePRxcoilmeasuredat360kHzbeforeitisassembledintoa
completecoilmodule(nomagneticshieldingorferritepresent).The valueissetto1.0becausethemeasurementis
takeninfreeair(andnotimpactedbymatedproducts);thisvaluemaychangeinfuturereleases.

5.2.2 MPLAPTxSpecifications
ThesearetheMPLAspecificationsforPTx.Inspecs4,6,9,10,12and14,theTPRistoreportPPR,estinsteadofPPRto
ensurethePTxMPLAimplementationhassufficientmarginandFOdetectionisworkingasexpected.ThePPR,estvalues
arederivedfromtheSection5.11.5,PowerLossAccountingComplianceTesting.
Testscenarios1and2aredescribedinSection5.8,FODetectionThresholds.Inthe
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