`
`STANDARDS PROJECT:
`
`IEEE 802.3 DTE Power via MDI Study Group
`
`
`
`CONTRIBUTION TITLE: Proposed DC Power Requirements for Power via MDI
`
`
`
`SOURCE:
`
`Circa Communications Ltd.
`1000 West 14th Street
`North Vancouver, BC
`Canada V7P 3P3
`
`
`
`CONTACT:
`Phone:
`Fax:
`Internet:
`
`Phil Holland
`(604) 990-5415
`(604) 990-5475
`Phil.Holland@Circa.CA
`
`
`
`DATE:
`
`September 31, 1999
`
`
`
`DISTRIBUTION TO:
`
`IEEE 802.3 DTE Power via MDI Study Group
`
`
`
`This submission have been formulated to assist the IEEE 802.3 DTE Power via MDI Study
`Group. This document is offered to the study group as a basis for discussion and is not
`binding on the Contributor. The requirements are subject to change in form after more
`study. The Contributor specifically reserves the rights to add to, or amend, the qualitative
`statements herein. Nothing contained herein shall be construed as conferring by implication,
`estoppel, or otherwise any license or right under any patent, whether or not the use of
`information herein necessarily employs an invention of any existing or later issued patent.
`
`The contributor grants a free, irrevocable, non-exclusive license to the IEEE 802.3 DTE
`Power via MDI Study Group to incorporate text contained in this contribution and any
`modifications thereof in the creation of a standards publication; to copyright in IEEE’s name
`any standards publication even though it may include portions of this contribution; and at
`IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE
`standards publication.
`
`SONY EXHIBIT 1015
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`Page 1 of 11
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`Page 2 of 11
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`Power via MDI Contribution
`
`Proposed DC Power Requirements for Power via MDI
`
`Contribution to the
`IEEE 802.3 DTE Power via MDI Study Group
`
`September 31, 1999
`
`TABLE OF CONTENTS
`
`1.
`2.
`
`3.
`
`INTRODUCTION ........................................................................................................ 2
`DC CAPABILITIES OF EXISTING LAN COMPONENTS ........................................... 3
`2.1. WIRING.................................................................................................................... 3
`2.2. CONNECTORS ......................................................................................................... 3
`2.3. POWER LIMIT IMPOSED BY EXISTING LAN COMPONENTS...................................... 4
`2.4. SAFETY CONSIDERATIONS...................................................................................... 4
`2.5. FORESEEABLE MISUSE ........................................................................................... 5
`POWER SOURCE/SINK OBJECTIVES AND CHARACTERISTICS .......................... 6
`3.1. EASY MIGRATION TO LAN POWERED DEVICES ...................................................... 6
`3.2. MAXIMIZE THE POWER RANGE................................................................................ 6
`3.3. POWER MANAGEMENT CONSIDERATIONS.............................................................. 7
`3.4. OUTLINE OF A PROPOSED POWER MANAGEMENT METHODOLOGY....................... 8
`
`Circa Communications Ltd.
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`1. Introduction
`
`Power via MDI Contribution
`
`The installation and user benefits provided by being able to power products such as
`telephones via a LAN are significant and will be important to the successful deployment of
`these new products. While obvious for products such as telephones, the same benefits are
`applicable to many products. The range of products that could be supported will only be
`limited by the maximum power that can be provided. For example, a laptop could be
`powered via the LAN or a desktop PC could be held up by a centrally located UPS.
`
`With the intent of enfranchising the widest range of products, this contribution focuses on
`the DC characteristics including safety, foreseeable misuse and power management issues
`that will allow a wide range of power to be provided via the LAN wiring. The contribution
`assumes that power could be provided via a single pair of wire or via a phantom powering
`configuration that would use two or more pairs of wire.
`
`It is also assumed that power could be provided to or from devices such as servers, hubs or
`routers. For example, a recognized need in IP telephony applications is to power a
`remotely located hub or switch which could in turn power the telephones connected to it. A
`conclusion based on this example is that the need to support a wide range of power levels
`and the ability to power at least one level of intermediate device will be key to the successful
`mass deployment of products such as LAN based point of sale terminals and telephone
`systems which will consist of large numbers of terminals. To be economically viable,
`support for a wide power range and the powering of intermediate devices must not place
`any economic burdens on the low power systems that will make up the majority of the
`market.
`
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`2. DC Capabilities of Existing LAN Components
`
`Power via MDI Contribution
`
`To be practical, any methodology used to deliver power via LAN wiring should be
`compatible with the wiring and connector systems that are in place today. In the sections
`that follow, the system components are considered in terms of any limitation that they may
`place on the power that can be delivered to a particular LAN device.
`
`2.1. Wiring
`
`The most common wire used today is 24 AWG Category 3 and 5 cable but some 26 AWG
`cable is still in use. Based on a maximum length of 100 meters the DC characteristics are;
`
`For 24 AWG and 26 AWG wire the resistance ranges from 8 to 9 ohms or 12 to 14 ohms
`per 100 meters respectively. The highest resistance is for solid wire, which is also the most
`commonly used type for the longest sections of a given run. Assuming that 26 AWG wire
`must be supported, a loop resistance of 18 ohms per 100 meters should be used as a worst
`case.
`
`• For single conductor, the rated current carrying capacity is 4 and 6 amperes for 26
`and 24 AWG wire respectively. While this may seem high, it must be derated
`significantly to limit the temperature rise when used in bundles. When you consider
`that bundles of a 100 or more 4 pair cables are common in LAN wiring the derating
`factor will reduce the practical current to less than 1 A. For example, a bundle of
`100 category 5 cables (24 AWG) that supplies 1.5 amps to a device connected to
`each cable via a phantom powering scheme that uses 4 conductors (0.75 A each),
`will have in internal temperature rise of 20°C. This temperature rise would place a
`realistic current limit on most installations.
`
`• Older wiring used in data networks was designed to be used with analog telephone
`systems and had to carry DC voltages of up to 105 volts with superimposed ring
`voltages of 90 volts RMS and was rated at 150 volts. Newer wiring is more
`commonly rated at 350 volts or better.
`
`2.2. Connectors
`
`Specifications for the eight position modular plugs and jacks used in LANs vary widely but
`even the lower ratings will provide good DC performance.
`
`• Current carrying capacity ratings typically range from 1 to 2.5 amps. Some
`manufacturers also derate this capacity to as little as 0.2 A as a function of
`temperature or total current carried by all the contacts in the connector. Assuming
`an ambient temperature of 50° C, a practical upper limit is 0.75 A per contact.
`
`• Modular connectors were originally designed to withstand the high voltages
`produced by ringing generators as well as the 1,000 to 1,500 volt lightning surges so
`in spite of their small size, will handle high voltages. The eight position modular
`plugs and jacks used for data networks inherited this construction and have
`regulatory agency ratings of 150 volts.
`
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`2.3. Power Limit Imposed by Existing LAN Components
`
`If the wiring system limitations above are considered, the power that can be delivered to a
`device on a LAN is considerable. This is shown in the table below.
`
`Power via MDI Contribution
`
`Parameter
`
`Dedicated Single
`Phantom Power
`Pair
`(2 pair)
`24 AWG 26 AWG 24 AWG 26 AWG
`150 Volts 150 Volts
`150Volts
`150Volts
`1.5 A
`1.2 A
`1 A
`0.8 A
`225 W
`180 W
`150 W
`120 W
`
`Conductor Size
`Supply Voltage
`Supply Current
`Supply Power
`(Max)
`28.5 Ω
`18 Ω
`14.3 Ω
`9 Ω
`Cable Resistance
`22.8 V
`18 V
`17.2 V
`13.5 V
`Voltage Drop
`18 W
`18 W
`20 W
`20 W
`Cable Loss
`102 W
`132 W
`160 W
`205 W
`Load Power (Max)
`Table 1 Power Limits and Dissipation for Common LAN Wiring Systems
`
`Please note that the maximum current used in Table 1 is based on temperature rise rather
`than connector current ratings. While it is unlikely that all the cables in a bundle would be
`fully loaded, it is possible, so the limitation has been used in this example.
`
`2.4. Safety Considerations
`
`Safety agencies are most concerned about minimizing the risks to users, installer etc, from
`product hazards. These include electric shock and energy hazards, thermal hazards, and
`fire hazards. While requirements may vary from country to country, IEC950 and the
`national variants of it are internationally accepted. For this reason, IEC 950 has been used
`to establish the limits used for this contribution.
`
`In IEC 950, the requirements for the protection against electric shock are based on the
`circuit configuration (grounded, ungrounded, level of pollution) and the operating voltage.
`While all of the voltages used to power network devices can all be considered hazardous,
`the requirements for systems operating at less than 60 volts DC and that conform to the
`requirements for SELV circuits are considerably less stringent than those operating above
`60 Volts.
`
`For operating voltages of less than 60 volts that are well isolated (double or reinforced
`primary insulation) from the mains, only operational insulation, (no insulation in some cases)
`is required between the SELV supply voltage and the user. Suitable insulation is likely to
`exist in most LAN interfaces today.
`
`For an ungrounded device operating above 60 volts, the insulation system used to provide
`protection for the user must be double or reinforced. While double or reinforced insulation
`can be provided by the housing for simple devices and is easily provided with modern wiring
`products such as double insulated wire, factors such as transformer size will be affected.
`As such, there will be an additional cost involved for products that operate for supplies that
`are higher than 60 volts. To ensure that these factors do not place a burden on low voltage
`products, it will be desirable to have at least two classes of power systems. The most
`common would be a lower power system that would be based on a maximum of input 60
`volts and a special purpose higher power scheme based on supply voltages over 60 volts
`but under the 150 volt limit set by the connectors.
`
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`Power via MDI Contribution
`
`2.5. Foreseeable Misuse
`
`In addition to the mandated safety requirements, there are a lot of common sense factors
`that should be considered. These can be safety related or simply an annoyance. Some
`examples include:
`
`Eight position modular connectors are small enough to be easily placed in a child’s mouth.
`As LAN appliances proliferate and powering via the LAN becomes more common this will
`happen. Even though there are no mandated requirements to prevent this and studies have
`shown that the resulting shock is not likely to be lethal due to the close spacing of the pins
`relative to any other return path, the voltages and currents involved will cause serious
`burns. A prudent design would therefore try to devise a way to reduce the likelihood of such
`an incident. One way to fulfill this objective is to ensure that power is not supplied to circuits
`that are not connected to a device that can be recognized by the power source.
`
`While originally intended for use in telecom systems, eight position modular connectors are
`not special use connectors. Unlike mains plugs that should only be used in a recognized
`manner, eight position modular connectors are used in a variety of applications including
`telephony products, LAN connections, barcode scanners and keyboards. While there is a
`possibility that a hazard (shock or fire) could be created by the accidental misuse of any
`combination of these devices on a powered LAN connection, it is more likely that the result
`would be damage to the device or power source. Neither is desirable so the LAN power
`system should be designed to minimize damage caused to other products including LAN
`interfaces with terminations that can be destroyed by even a moderate power source. Once
`again, this objective can be satisfied if power is not supplied to circuits that are not
`connected to a device that can be recognized by the power source.
`
`Offices often have several LAN connections in a single wall plate. It is therefore
`foreseeable that two powered LAN connections will be interconnected with either LAN cable
`or some other type of cable with an unknown connection scheme. This should not cause
`damage to the system.
`
`It is foreseeable that devices intended to be powered from a supply located somewhere on
`the LAN could be plugged into 8 position modular jacks intended for non-LAN devices.
`These could include powered ISDN jacks or basic analog telephone circuits which
`commonly use 8 position connectors when 2 to 4 lines (RJ-13 ?) are terminated on a single
`connector. While it is unlikely that the LAN device would damage any of the power sources,
`these power sources may present voltages as high as 200 volts peak with output currents
`as high as 0.5 A and could damage the LAN device. To minimize potential damage, the
`LAN device must be polarity and over voltage protected. It would also be desirable for the
`LAN device not to power up unless it can determine that it is connected to a recognized
`power source. This would also allow the device to indicate to the user that it is powered and
`has a valid LAN connection.
`
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`3. Power Source/Sink Objectives and Characteristics
`
`Power via MDI Contribution
`
`3.1. Easy Migration to LAN Powered Devices
`
`To allow an easy migration to LAN powered devices, the proposed Source and Sink
`characteristics have been designed to limit the changes to the circuitry needed to support
`the addition of power to the LAN. Changes to existing MACs or PHYs have not been
`proposed to avoid making the wide range of existing parts obsolete. This is particularly
`important for new devices such as those for LAN telephones that are available now or in the
`near future that have single or dual embedded network interfaces.
`
`An important factor in the migration to LAN powered devices is the ability to support higher
`powered or intermediate devices without placing a cost burden on the multitude of low
`power devices that will exist. This can be done by providing high and low power categories
`and a means of ensuring interoperability is provided. This contribution proposes three
`categories and a means of ensuring that only valid combinations of Sources and Sinks will
`inter-operate. Initially the three categories can be managed by the power Sources and
`Sinks themselves but migration to more intelligent management can be supported in the
`future
`
`3.2. Maximize the power range.
`
`In Table 1, the thermal limits of large bundles of cables limited the power that can be
`delivered to a device connected to a LAN were described. These maximums ranged from
`102 W to 205 W and were dependent on the powering configuration and wire gauge. To
`simplify the safety requirements for lower power, cost sensitive devices, this has been
`divided into a low voltage and high voltage category. Based on the maximum 60 volt limit
`for SELV circuitry the low voltage source category must have an upper limit of 60 volts. It is
`proposed that the nominal voltage therefore be set at 55 ± 5 volts. Allowing reasonable
`tolerances, the proposed high voltage category source voltage is 135 ± 15 volts. To ensure
`that the temperature rise for #26 AWG wire is reasonable a maximum load current of 1.2 A
`or 0.6 A per conductor has been assumed. This limits the Source Power to 66 W for the
`low voltage category and 162 W for the High Voltage category. Assuming that the cable
`can be 26 AWG, the maximum power that will be delivered and therefore the limit to be
`consumed by the Sink device is 45 W for the Low Voltage category devices and 141 W for
`the High Voltage category. This is summarized in the table that follows.
`
`Parameter
`
`Phantom Power
`Phantom Power
`(2 pair) High
`(2 pair) Low
`Voltage
`Voltage
`24 AWG 26 AWG 24 AWG 26 AWG
`Conductor Size
`55 Volts
`55 Volts
`135 Volts 135 Volts
`Supply Voltage
`1.2 A
`1.2 A
`1.2 A
`1.2 A
`Supply Current
`66 W
`66 W
`162 W
`162 W
`Supply Power
`9 Ω
`14.3 Ω
`9 Ω
`14.3 Ω
`Cable Resistance
`10.8 V
`17 V
`10.8 V
`17 V
`Voltage Drop
`13 W
`20.6 W
`13 W
`20.6 W
`Cable Loss (100 M)
`53 W
`45 W
`149 W
`141 W
`Load Power (Max)
`Table 2 Practical LAN Power Capabilities
`
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`Power via MDI Contribution
`For many devices, the power that can be delivered and what is actually required will be very
`different. Many devices, such as telephones will only require power levels below 5 watts so
`the Source should not always be required to support higher power levels. To recognize this,
`a Low Power, Low Voltage category is proposed. The characteristics of the three
`categories proposed are:
`
`Category
`Characteristic
`3
`2
`1
`135 V
`55 V
`55 V
`Source Voltage
`162 W
`66 W
`5.1W
`Source Power (max)
`20.6 W
`20.6 W
`0.12 W
`Cable Loss (100 M)
`141W
`45 W
`5 W
`Sink Power (max)
`Table 3 Proposed Source and Sink Power Categories
`
`3.3. Power Management Considerations
`
`When considering a power management methodology a wide range of requirements
`including design practicality and cost must be evaluated. Some of the factors that were
`considered for the power management scheme proposed were:
`
`a) For safety and reliability reasons, power should only be provided when the Source
`has determined that a valid Sink has been connected. Due to the unknown
`characteristics of the wide variety of products that use 8 position modular
`connectors, this can only be done by looking for a unique Sink signature.
`
`b) For reliability reasons, It is desirable that the Sink only accepts power when it is
`connected to a recognized Source. This can be done by requiring the Sink to only
`respond to a recognized power up sequence.
`
`c) It should not be assumed that all devices will be able to support management
`protocols. This complicates the administration of any product such as LAN
`telephones and adds a cost burden that may be unacceptable on low cost (under
`$30) devices.
`
`d) Higher power devices should be supported without any burden being placed on the
`more common low power devices.
`
`e) Power may be inserted and removed by devices that are separate from the network
`interface. As such the power management methodology should be independent
`from the MAC or PHY. This is also important because it avoids making the wide
`range of low cost LAN silicon in use now obsolete for powered devices. It is also
`important because it provides the ability to move the burden that high currents will
`place on LAN isolating transformers to external devices that are only provided when
`more power is required. This is most applicable to applications where the power
`provided by the LAN wiring exceeds 5 watts.
`
`f) LAN connections are isolated so it is expected that Sinks and Sources will also have
`to be isolated. As a practical design consideration the basic Sink and Source
`management should be located on the cable side of the connection so that the need
`to provide more costly isolated control lines for these devices can be avoided.
`
`g) LAN power Sources will be provided as primary power and as backup power to
`devices that may be locally powered. When a Source is used for backup power, its
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`Power via MDI Contribution
`removal and application must be able to be accomplished while the device is
`operating and should not impair normal operation.
`
`h) It should be assumed that some ports could be a Source or a Sink and that the
`functional determination could be automatic.
`
`i) A power management methodology should not require system intelligence nor
`should it preclude its use.
`
`j) Continuous operation of a power management system should not be dependent on
`the device operating system. For example, a reset or reboot should not affect normal
`operation of the power management system unless this is a specifically intended
`interaction.
`
`k) The 8 position modular connectors were designed primarily for low current
`applications and some designs may not tolerate the high inrush current currents that
`can be caused when capacitor is charged from a voltage source. The power
`management system should ensure that these inrush current do not occur.
`
`3.4. Outline of a Proposed Power Management Methodology
`
`Adding the three power categories proposed in Table 3, places even more requirements on
`the power management system. For example, a device with a type 1 Sink could be
`powered from a type 1 or 2 Source. If designed with an adequate input voltage and
`insulation system, it could also be powered from a type 3 Source. A type 2 device could be
`powered from a type 2 Source or if designed with an adequate input voltage and insulation
`system from a type 3 Source. A type 2 device cannot be used with a type one Source
`because it requires more power than the Source may be able to provide. Due to the high
`power requirement for a type 3 device, it can only be powered from a type 3 source. In the
`future, an intelligent power management methodology could be used to allow a device to
`power up as a type 1 or 2 device and then request and confirm that a specific power be
`allocated to it before switching to a high power category.
`
`This contribution proposes the use of a DC signature to identify the Sink type and the Sink
`may use the specific power up sequence characteristics of the Source to determine if it
`should draw power. While this may seem complex, these functions can be performed with
`simple Source and Sink circuitry that doesn’t require changes to the existing integrated
`circuits used in most LAN circuitry. An intelligent system based management is also not
`required but the use of such systems is not precluded. In the case of the Sink, the power
`management function is envisioned as a functionality that could be added to the switching
`regulator that will be used to pass power over the isolation barrier required in most products.
`
`As proposed, the signature for a Sink circuit consists of three parts. At low voltages (less
`than 5 volts) the Sink must present a high resistance (greater than 10K) to the Source.
`During a transitional phase from low voltage to operating voltage it must preset a constant
`current load or pilot current that is used to identify the type 1 or 2 category of the Sink. A
`voltage clamp in type 1 and 2 Sinks is used to separate them from type 3 Sinks. This clamp
`is also required to ensure that the SELV circuit characteristics of type 1 and 2 devices
`cannot be exceeded in the event of a single fault. The fault could be the result of a failure in
`a type 3 Source.
`
`The low voltage characteristic of the Sink is provided to allow the source to detect devices
`such as termination resistors that could be damaged by the Source. The pilot current is
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`Power via MDI Contribution
`used to detect other types of power sinks such as power supplies or surge protectors that
`may exist in non-LAN devices.
`
`To detect the signature of the Sink, the Source and Sink go through a specific power up
`sequence. The basic sequence includes the following steps;
`
`With no current flowing from the Source, it reverts to a 6 volt (the actual voltages current
`used could vary from those used in the example) with the output current limited to 2 mA at 3
`volts or higher and but decreases to 0.5 mA at 0 volts. When a 1 mA pilot current is
`detected by the Source, the output voltage starts a transition to the operating voltage.
`During this transition, the pilot current must remain within a valid range. If the pilot current
`goes outside the valid range the output is reset to the 3 volts. It remains there until the load
`current is removed. If the pilot current remains within the valid range the Source output
`rises to the normal output voltage and the current limit is increased to the normal running
`current that the source is capable of providing. The Source is now in full power mode and
`will remain there until the load current falls below the pilot current or exceeds the maximum
`output current for more than a few hundred milliseconds. If this happens the Source resets
`and starts the initialization sequence again.
`
`A Sink starts to power up when a voltage is applied by the source but remains in the low
`pilot current state for a few hundred milliseconds after the nominal operating voltage is
`reached. It then switches run state and latches. It will stay in the run state as long as the
`operating voltage remains in the valid range. If the input voltage drops below the minimum
`for more than a few hundred milliseconds, the Sink will reset and reapply the pilot current
`until the operating voltage returns to normal.
`
`If it is desirable to have the Sink only draw power from a recognized Source, the slew rate
`of the transitional phase used to measure the pilot current can be define by the standard
`and used as a Source signature.
`
`A type 2 device is distinguished from a type 1 device by the pilot current. The type 2 Sink
`has a higher pilot current and will cause the transitional Current limit of a type 1 Source to
`be exceeded. When this happens, the Source will reset to the low voltage state. However,
`the lower pilot current of a type 1 device will allow it to operate from a type 1 or 2 Source.
`To comply with the requirements for an SELV circuit, a Sink must be able to maintain the
`SELV voltage limits at all times. This includes conditions where a single fault has occurred.
`One way of doing this is by providing a voltage clamp (such as a zener or thyristor
`protection device) at the input of a type 1 or 2 device that does not have an adequate
`insulation system to qualify as a type 3 Sink. While provided as part of the basic safety
`system, this clamp limits the transition voltage (causes the pilot current to be exceeded)
`which causes a type 3 source to reset to the low voltage state if an incompatible type 1 or 2
`device is connected.
`
`While not suggested as a requirement, a single connection can be designed to act as a
`Source or as a Sink. When a device is powered via the mains connection, the port
`functions as a Source. When mains power is not available, the port acts as a Sink and may
`draw power from a unit that has central battery backup. If both devices are mains powered,
`the ports both function as Sources and will remain that way until one port starts to draw pilot
`current
`
`While basic, this power management methodology will facilitate the use of different power
`category Sink and Source devices without placing a cost burden on the low power devices
`while allowing applications that do need considerably more than 5 or 6 watts to obtain it via
`a compatible powering system.
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