oSIST prEN IEC 63758-5-4:2026

• Status: Not Published
• Public Enquiry End Date: 29-Nov-2026
• ICS: 29.240.99 - Other equipment related to power transmission and distribution networks
• ICS: 33.160.99 - Other audio, video and audiovisual equipment
• ICS: 35.200 - Interface and interconnection equipment
• Technical Committee: AVM - Audio, video and multimedia systems and equipment
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 28-Sep-2026
• Due Date: 15-Feb-2027
• 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: prEN IEC 63758-5-4:2026 - Qi specification - Version 2.3 - Part 5-4: Mpp - Foreign object detection (Fast Track)

oSIST prEN IEC 63758-5-4:2026 is the SIST publication that is identical to prEN IEC 63758-5-4:2026 for Qi Specification - Version 2.3 - Part 5-4, MPP - Foreign object detection. It specifies how Qi MPP systems detect foreign objects in the magnetic power-transfer field so power transmitters and power receivers can avoid heating metal objects during startup, mating, and power transfer.

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

oSIST prEN IEC 63758-5-4:2026 specifies a set of foreign object detection methods for Qi MPP, with separate handling for pre-power-transfer, mated, and in-power-transfer cases. The document is organized around the detection method, the associated negotiation and packet exchange, and the calibration and error-budget logic needed to decide when power may continue safely.

The main structure is:

• Clause 1 - General rules, scope, compliance wording, notation, tolerances, packet-field conventions, and shorthand notation.
• Clause 2 - ForeignObjectDetection background and the role of the different detection steps.
• Clause 3 - Open-air Q-Test for detecting a foreign object before power transfer begins.
• Clause 4 - MatedQ-DeflectionTest for detecting a foreign object when the PRx is placed on the PTx.
• Clause 5 - MPPPowerLossAccounting (MPLA) for in-power-transfer foreign object detection.
• Clause 6 - MPLAImprovementsforPowerModes (MPLA2), an updated accounting model for power modes.
• Clause 7 - DPLOSS, a calibration-based in-power-transfer method that extends power transfer above 15W.
• Clause 8 - GGValueDefinitions for the nominal coefficient values used with the test-tool coils.

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

Before power transfer

oSIST prEN IEC 63758-5-4:2026 uses Open-air Q-Test to compare run-time Q against a free-air baseline before power transfer starts. The practical purpose is simple: if a foreign object is already on the PTx, the transmitter can detect that condition before energy is applied.

Clause 3 explains that Open-air Q-Test is not a substitute for the in-power-transfer methods. It will not catch every insertion sequence, so the document ties it to the later methods rather than using it alone.

Clause 3 also introduces the MovementTimer and SettlingTimer. The MovementTimer is meant to avoid false foreign object flags while a receiver is still sliding into place, and the settling logic delays digital ping until the Q deflection has stabilized. In practice, this protects normal user placement from being mistaken for a fault.

Clause 3 recommends periodic testing during standby and says the transmitter should treat a failed or absent open-air test as a foreign-object condition for power-limit purposes. That matters because the later in-power method must know whether it can rely on a clean pre-power check.

When the PRx is being mated

oSIST prEN IEC 63758-5-4:2026 uses MatedQ-DeflectionTest when the PRx arrives on the PTx and the system has already collected settled open-air measurements. This method compares the mated response against the expected response and is intended for the tighter magnetic state space of MPP.

Clause 4 requires the PTx to set the FO field to 2 in MATEDQ_RES when a foreign object is placed at a position that would lead to overheating. It also says the PTx shall not enter DeltaPloss calibration if a foreign object is detected. In practice, that prevents the system from calibrating on a contaminated setup.

Clause 4 also requires the PRx to send valid parameters in MATEDQ_COEFF during both the 128 kHz and 360 kHz negotiation phases. That means the receiver has to participate in the setup, not just the transmitter.

The threshold method in Clause 4 depends on per-unit calibration against a reference PRx coil and ecosystem scaling. The practical takeaway is that manufacturers need reference measurements and stored coefficients if they want the method to separate a normal mated pair from a foreign-object case.

During power transfer

oSIST prEN IEC 63758-5-4:2026 defines MPLA as the in-power-transfer foreign object detection method for MPP. Clause 5 uses exchanged parameters, packet reports, and coil-loss estimation to decide whether power should continue or be reduced.

Clause 5 requires the PTx and PRx to exchange MPLA parameters during negotiation, and the PRx shall measure and report its power in the PLA packet. The document also sets different operating expectations inside the 2x2 cylinder and outside it. In practice, that means a transmitter must keep normal transfer stable near the center while becoming more conservative as coupling worsens.

Clause 5 requires the PTx to reduce transmitted power within 8 seconds if a foreign object is present. While throttling, the PTx sends NAK to PLA packets and maintains or decreases its equivalent inverter voltage. That matters because the system must back off quickly enough to protect the object, but not so abruptly that it becomes unusable.

Clause 5 also ties MPLA to accessory effects, coil-current measurement, and an error budget. Phone cases and other passive accessories can change the loss picture, so the standard explicitly treats them as part of the implementation problem rather than ignoring them.

For higher power modes and calibration-based operation

oSIST prEN IEC 63758-5-4:2026 introduces MPLA2 in Clause 6 to improve the loss model for power modes. MPLA2 uses PLA_2 and PowerLossAccountingParameters2, but it keeps the same safety intent: detect a foreign object, control power, and avoid overheating.

Clause 6 keeps the same basic transmitter behavior inside the 2x2 cylinder when no foreign object is present, and it still requires the PTx to reduce power within 8 seconds if a foreign object is present. The receiver also has to negotiate PLA Format 2 when the transmitter supports it.

Clause 7 defines DPLOSS for power transfer above 15W after calibration. The document requires the PTx to limit negotiable power to 15W until calibration is complete, use a minimum of three power levels for calibration, accept a minimum number of calibration points, and keep the calibration time within the specified limit. In practice, DPLOSS is the higher-power path, but it only works if the calibration routine is controlled and repeatable.

Clause 7 also says the system shall reduce power within 8 seconds when a foreign object enters the interface volume, and it provides fallback behavior if the threshold is exceeded. That means the transmitter can continue operating above 15W only while the calibrated loss model remains valid.

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

• foreign object (FO) - An object in the magnetic field that can heat during power transfer and trigger foreign object detection.
• Power Transmitter (PTx) - The unit that creates the wireless power field and decides whether to start, continue, or reduce power.
• Power Receiver (PRx) - The unit that receives wireless power and sends measurement data back to the transmitter.
• Open-air Q-Test - The pre-power-transfer method that compares run-time Q to a free-air reference.
• MatedQ-DeflectionTest - The method that evaluates Q deflection after the PRx has been placed on the PTx.
• MPLA - MPPPowerLossAccounting, the in-power-transfer method that estimates foreign-object risk from exchanged loss data.
• DPLOSS - Delta Ploss, the calibration-based method that tracks changes in power-loss estimates during transfer.
• PLA / PLA_2 - The packet formats used to exchange power-loss accounting data between PTx and PRx.

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

oSIST prEN IEC 63758-5-4:2026 is used by designers and validators of Qi wireless power systems, especially for flat-surface devices such as mobile phones and chargers operating at power levels up to 25W. It is also relevant to accessory makers because cases and other passive items can change the loss behavior.

Typical users include:

• PTx and PRx hardware designers
• firmware engineers implementing ping, negotiation, throttling, and packet exchange
• compliance and test laboratories
• quality managers checking calibration, threshold behavior, and error budgets
• buyers or product teams writing interoperability and safety requirements for Qi MPP products

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

• ISO/IEC Directives, Part 2 - Sets the wording rules behind shall, should, may, and can.
• IEC 62368-1:2018 - Provides the thermal burn injury safety context used when the document sets or discusses foreign-object power limits.
• Qi Specification - Communications Protocol - Supplies packet naming, negotiation behavior, and packet fields such as GET[MATEDQ], PLA, and PLA_2.
• Qi Specification - Power Delivery - Supplies the power-delivery context used for K estimation, equivalent inverter voltage, and timing alignment.
• Qi Specification - Foreign Object Detection book - Provides the companion measurement methods for Q, ring-down behavior, and the annexes referenced by this part.
• MPP Design Guidelines (Informative) - Provides the power-loss split model and related design background used in MPLA and DPLOSS calculations.

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

The document contains the rules for packet notation, numeric format, tolerances, and big-endian field layout, plus the shorthand notation for data packets. It also contains the background flowcharts and timing logic for Open-air Q-Test, including movement and settling behavior.

It includes methods, equations, and worked examples for MatedQ threshold calculation, ecosystem scaling, coefficient extraction, and distance-based decision boundaries. It also contains the MPLA and MPLA2 loss models, including parameter exchange, error-budget development, accessory effects, coil-current measurement, and compliance testing.

Figures and tables cover the major implementation topics: Q measurement, bias ping, threshold selection, calibration planes, error distributions, and compliance-test shifters. Table 4 defines parameter representation, Table 5 covers ecosystem scaling terms, and Tables 8 to 11 collect error-budget values and nominal coefficients for the test-tool reference coils.

Clause 7 adds the DPLOSS calibration procedure, linear calibration checks, fit-error checks, and the handling of switched-capacitor-based PRx systems. Clause 8 closes with nominal GG values for MPLA, MPLA2, and MatedQ reference coefficients used in testing and calibration.

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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