ON Semiconductor NCP1095GEVB User manual

©Semiconductor Components Industries, LLC, 2019
June, 2019 −Rev. 0
1Publication Order Number:
EVBUM2644/D
NCP1095GEVB
NCP1095 Evaluation Board
User's Manual
IEEE 802.3bt PoE-PD Interface Controller
Board
General
The NCP1095GEVB board allows easy implementation
and evaluation of a Power-over-Ethernet powered
equipment that is able to operate with an assigned power
level up to 90 W. The evaluation board is based on the PoE
PD Controller NCP1095 (U2) that uses an external
pass-switch (Q1) and sense resistor (R10). The board can
also facilitate the design of proprietary 100 W+
applications.
Figure 1. Operational NCP1095GEVB Showing
Basic Interconnections
The NCP1095GEVB board is designed as a PoE splitter:
having a PoE-enabled Ethernet port (labeled “PoE IN”) as
input and offering the power to a separate connector (J2)
while passing through the data to another Ethernet port
(labeled “E OUT”).
Quick Start Guide
Step 1: Connect the power connections available on
connector J2 (labeled “GND” and “VPP”) to the DC/DC
converter on the system that needs to be powered (cf. black
and red wires in the picture on the left). The 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 connector J2 could be used (cf. green wire in the
picture on the left). The “PG” signal will be clamped to 18 V
by a zener when the board is powered up. For some DC-DC
converter boards an additional diode in series with the
control connection might be required (cathode connected to
NCP1095 and anode connected to the DC-DC converter).
For a DC-DC converter with an active low enable (EN or
SHDN or ON/OFF), the “nPG” signal on P1 could be used.
The “nPG” signal will be pulled up to VPP during the inrush
phase. Always check the voltage rating of the enable,
shutdown or undervoltage pin of the DC-DC converter.
Step 3: Insert the Ethernet cable (cf. blue cable in the picture
on the left) coming from the PSE in the Ethernet connector
J3 labeled “PoE IN”.
If the PSE powers up the system the green PGOOD LED
should be ON.
The status of the remaining LEDs depends on the PSE
being used.
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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 1 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.

NCP1095GEVB
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Figure 2. Schematic Diagram NCP1095 EVB

NCP1095GEVB
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Auxiliary Supply
The NCP1095GEVB supports drawing power from an
alternate or local power source in applications connected to
non-PoE enabled networks. A rear auxiliary supply can be
inserted in connector J6 labeled “P IN”.
The recommended voltage of the auxiliary supply is 24 V.
Table 3. ELECTRICAL CHARACTERISTICS
Operating Range
Auxiliary Input Voltage 20−30 V
Auxiliary Input Current 0–5 A
Auxiliary Input Voltage,
Extended [Warning!]
10–57 V
If an auxiliary supply that is too low (10.1 V …20 V) is
inserted before the UVLO threshold was crossed by the PSE,
the class driver could become unintentionally activated.
Therefore it is recommended to adapt the AUX resistor
divider to R22 = 33 kWand R23 = 15 kWfor operation with
a low voltage auxiliary supply voltage.
The NCP1095GEVB is able to operate with an auxiliary
supply voltage up to 57 V. However the customer must take
caution when using a high voltage (>30 V) auxiliary supply:
the NCP1095GEVB has to be unpowered when this high
voltage (30 V …57 V) supply is inserted.
Do not insert 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 auxiliary supply can be inserted
while the PD is already powered by the PSE, both
GreenBridge2 rectifiers (U1 and U3) need a gate drive
circuit allowing them to be disabled. Figure 4 shows a gate
drive circuit (GDC) able to turn off the GreenBridge2
internal top MOSFETs.
Figure 4. Basic GreenBridge2 GDC with disable
G4
G3
G1
G2
IN1 IN2
BC846BPDW1
DF6A6.8FUT1G
NCP1095_GBR
½BAV70LT1G
1.5M
BC846BPDW1
1.5M
If the AUX input pin of NCP1095 is pulled high, it will
immediately drive the GBR pin low. The above gate drive
circuit controlled by the GBR pin makes sure the PD does
not source power under any circumstance in combination
with a high voltage (>30 V) auxiliary supply.
The gate drive circuit shown in Figure 4 is NOT
implemented on NCP1095GEVB. Therefore a high voltage
(>30 V) auxiliary supply should not be inserted when
NCP1095GEVB is already powered by a PSE.

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