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NCP1095GEVB

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Assigned Power

The NCP1095GEVB will request Class 8 during Physical

Layer classification. PDs need to take into account that they
can be underpowered and eventually be assigned to Class 3,
4 or 6.

The state of the NCM and NCL outputs provides

information about the power level that the PSE has assigned
to the NCP1095GEVB during classification. See Table to
determine the assigned power based on the status of the
orange NCM and NCL leds.

Table 1. CLASSIFICATION RESULT

NCM

Led

NCL

Led

Assigned

Class

Assigned

Power

off

off

3

13 W

off

on

4

25.5 W

on

off

6

51 W

on

on

8

71.3

90 W

PDs assigned to Class 8 may consume greater than 71.3 W

as long as they guarantee not to exceed the 90 W power limit
at the PSE power interface. Operation beyond 71.3 W is,
however, only possible if additional information is available
to the PD regarding the actual link section DC resistance
between the PSE and the PD.

The application should always operate at or below the

assigned power limit. Failure to do so will result in the PSE
disconnecting the PD!

PSE Categorization

The state of the LCF output provides information

(retrieved during classification) about the type of PSE the
NCP1095GEVB is connected to. See Table 2 to determine
the PSE Type based on the status of the red LCF led.

Table 2. PSE TYPE

LCF Led

PSE Categorization

off

The PSE is categorized according to 802.3af/at

(PSE Type 1 or Type 2)

on

The PSE is categorized according to 802.3bt

(PSE Type 3 or Type 4)

The PSE Type determines the MPS timing. It also

indicates to a PD requesting Autoclass whether it makes
sense to go to the maximum power state according to its
assigned Class.

System Startup

A PD can be underpowered and assigned to Class 3 only.
Therefore the DC/DC converter behind NCP1095GEVB

should not draw more than 13 W during start-up. Eventually
the soft-start setting of the DC/DC converter might need to
be adapted to accomplish this.

Requested Power

As mentioned before, the NCP1095GEVB will request

Class 8 during Physical Layer classification. If a lower Class
or power level is preferred, resistor R8 labeled “CLB”
and/or resistor R7 labeled “CLA” should be changed. See
the 

NCP1095 datasheet

 for the nominal resistance values.

The Class the PD is actually assigned to is always limited

to the requested Class.

Autoclass

The NCP1095GEVB will by default not request

Autoclass during Physical Layer classification. If the PD
should request Autoclass, remove 0E resistor R9 labeled
“acs”.

Maintain Power Signature (MPS)

A PD should draw a minimum amount of current in order

to prevent the PSE from removing power. The load resistor
R15 was added on the bottom side of the board to make sure
the load current is always sufficient and the NCP1095GEVB
remains powered.

Depending on the minimum current the system may draw,

the resistance value of R15 should be increased for the final
design in order not to waste power unnecessarily.

For some systems, the load resistor can even be omitted.

Содержание NCP1095GEVB

Страница 1: ...DC DC converter behind the NCP1095 EVB should be operational over a 34 V to 57 V voltage range Step 2 Connect the control connection to the DC DC converter It is important that the DC DC converter or any significant load is kept off when the pass switch is charging the input capacitance For a DC DC converter with an undervoltage UV or UVLO or an active high enable EN or SHDN the PG signal on conne...

Страница 2: ... 802 3af at PSE Type 1 or Type 2 on The PSE is categorized according to 802 3bt PSE Type 3 or Type 4 The PSE Type determines the MPS timing It also indicates to a PD requesting Autoclass whether it makes sense to go to the maximum power state according to its assigned Class System Startup A PD can be underpowered and assigned to Class 3 only Therefore the DC DC converter behind NCP1095GEVB should ...

Страница 3: ...NCP1095GEVB www onsemi com 3 Figure 2 Schematic Diagram NCP1095 EVB ...

Страница 4: ...nsert a high voltage 30 V auxiliary supply when the NCP1095GEVB is already powered by a PSE Violating the warning above may result in the PD sourcing power on the PoE IN Ethernet connector Figure 3 Operational NCP1095GEVB Showing Basic Interconnections G3 G2 BC846BPDW1 162K IN1 IN2 G4 G1 MMBZ27VALT1G BC846BPDW1 G3 If the customer needs to implement a system in which a high voltage 30 V rear auxili...

Страница 5: ... support systems or any FDA Class 3 medical devices or medical devices with a similar or equivalent classification in a foreign jurisdiction or any devices intended for implantation in the human body You agree to indemnify defend and hold harmless onsemi its directors officers employees representatives agents subsidiaries affiliates distributors and assigns against any and all liabilities losses c...

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