NCP1081_13 datasheet(11/18 Pages) ONSEMI

Part #	NCP1081

Description	Integrated High Power PoE-PD Interface & DC-DC Converter Contr

Download	18 Pages

Scroll/Zoom	100%

Manufacturer	ONSEMI [ON Semiconductor]

Direct Link	http://www.onsemi.com

Logo

11 / 18 page

NCP1081

http://onsemi.com

11

DESCRIPTION OF OPERATION

Powered Device Interface

The PD interface portion of the NCP1081 supports the

IEEE802.3af and 802.3at defined operating modes:

detection signature, current source classification, inrush and

operating current limits. In order to give more flexibility to

the user and also to keep control of the power dissipation in

the NCP1081, both current limits are configurable. The

device enters operation once its programmable Vuvlo_on

threshold is reached, and operation ceases when the supplied

voltage falls below the Vuvlo_off threshold. Sufficient

hysteresis and Uvlo filter time are provided to avoid false

power on/off cycles due to transient voltage drops on the

cable.

Detection

During the detection phase, the incremental equivalent

resistance seen by the PSE through the cable must be in the

IEEE802.3af standard specification range (23.75 k

W to

26.25 k

W) for a PSE voltage from 2.7 V to 10.1 V. In order

to compensate for the non-linear effect of the diode bridge

and satisfy the specification at low PSE voltage, the

NCP1081 presents a suitable impedance in parallel with the

25.5 k

W Rdet external resistor connected between VPORTP

and VPORTN. For some types of diodes (especially Schottky

diodes), it may be necessary to adjust this external resistor.

When the Detection_Off level is detected (typically

11.5 V) on VPORTP, the NCP1081 turns on its internal

3.3 V regulator and biasing circuitry in anticipation of the

classification phase as the next step.

Classification

Once the PSE device has detected the PD device, the

classification process begins. The NCP1081 is fully capable

of responding and completing all classification handshaking

procedures as described next.

Classification Current Source Generation

In classification, the PD regulates a constant current

source that is set by the external resistor RCLASS value on

the CLASS pin. Figure 6 shows the schematic overview of

the classification block. The current source is defined as:

Iclass +

Vbg

Rclass

, (where Vbg is 1.2 V)

CLASS

VDDA1

1.2 V

VPORTP

VPORTN1,2

NCP1081

Rclass

Figure 6. Classification Block Diagram

The NCP1081 can handle all defined types of

classification, IEEE802.3af, 802.3at and proprietary

classification.

In the IEEE802.3af standard the classification is

performed with a Single Event Layer 1 classification.

Depending on the current level set during that single event

the power level is determined. The IEEE802.3at standard

allows two ways of classification which can also be

combined. These two approaches enable higher power

applications through a variety of PSE equipment.

For power injectors and midspans a pure physical

hardware handshake is introduced called Two Event Layer 1

classification. This approach allows equipment that has no

data link between PSE and PD to classify as high power.

Since switches can establish a data link between PSE and

PD, a software handshake is possible. This type of

handshake is called Layer 2 classification (or Data Link

Layer classification). It has the main advantage of having a

finer power resolution and the ability for the PSE and PD to

participate in dynamic power allocation.

Table 4. Single and Dual Event Classification

Standard

Layer

Handshake

802.3af

1

Single event physical classification

802.3at

1

Two event physical classification

802.3at

2

Data-link (IP) communication

classification

One Event Layer 1 Classification

An IEEE802.3af compliant PSE performs only One Event

Layer 1 classification event by increasing the line voltage

into the classification range only once.

Two Event Layer 1 Classification

A IEEE802.3at compliant PSE using this physical

classification performs two classification events and looks

for the appropriate response from the PD to check if the PD

is IEEE802.3at compatible.

The PSE will generate the sequence described in Figure 7.

During the first classification finger, the PSE will measure

the classification current which should be 40 mA if the PD

is at compliant. If this is the case, the PSE will exit the

classification range and will force the line voltage into the

Mark Event range. Within this range, the PSE may check the

non-valid input signature presented by the PD (using the two

point measurement defined in the IEEE802.3af standard).

Then the PSE will repeat the same sequence with the second

classification finger. A PD which has detected the sequence

“Finger + Mark + Finger + Mark” knows the PSE is

IEEE802.3at compliant, meaning the PSE will deliver more

current on the port. (Note that a PSE IEEE802.3at compliant

may apply more than two fingers, but the final result will be

the same as two fingers).

Similar Part No. - NCP1081_13

Manufacturer	Part #	Datasheet	Description
ON Semiconductor	NCP1081DEG	239Kb / 17P	Integrated High Power PoE-PD Interface & DC-DC Converter Controller September, 2008 ??Rev. 4
ON Semiconductor	NCP1081DER2G	239Kb / 17P	Integrated High Power PoE-PD Interface & DC-DC Converter Controller September, 2008 ??Rev. 4

More results

Similar Description - NCP1081_13

Manufacturer	Part #	Datasheet	Description
ON Semiconductor	NCP1081	239Kb / 17P	Integrated High Power PoE-PD Interface & DC-DC Converter Controller September, 2008 ??Rev. 4
	NCP1083	263Kb / 18P	Integrated High Power PoE-PD Interface & DC-DC Converter Controller May, 2013 ??Rev. 3
	NCP1080	227Kb / 15P	Integrated PoE-PD & DC-DC Converter Controller May, 2013 ??Rev. 7
	NCP1080	207Kb / 14P	Integrated PoE-PD & DC-DC Converter Controller September, 2008 ??Rev. 4
	NCP1082	220Kb / 17P	Integrated PoE-PD & DC-DC Converter Controller May, 2013 ??Rev. 3
	NCP1083	246Kb / 17P	Integrated High Power PoE-PD Interface & DC-DC Converter Controller with 9V Auxiliary Supply Support November, 2008 ??Rev. 0
Murata Manufacturing Co...	MYBSP01206AZFT	12Mb / 13P	Isolated DC-DC converter for PoE PD 2018
Kinetic Technologies.	KTA1137A	980Kb / 22P	IEEE 802.3at PoE PD with Integrated DC-DC Controller November 2019 - Revision 04a
ON Semiconductor	NCP1082	201Kb / 16P	Integrated PoE-PD & DC-DC Converter Controller with 9V Auxiliary Supply Support November, 2008 ??Rev. 0
Bourns Electronic Solut...	POE-EP	1,007Kb / 8P	POE-EP & POE-PD Series - PoE DC/DC Transformers Mar 31, 2015

More results

NCP1081 Datasheet(PDF) 11 Page - ON Semiconductor

NCP1081 Datasheet(HTML) 11 Page - ON Semiconductor

Similar Part No. - NCP1081_13

Similar Description - NCP1081_13

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Datasheet Download

Link URL