ncp1081 ON Semiconductor, ncp1081 Datasheet - Page 4

• Manufacturer Part Number: ncp1081
• Description: Integrated High Power Poe-pd Interface & Dc-dc Converter Controller
• Manufacturer: ON Semiconductor

transformer to provide power to the NCP1081 DC−DC controller via its VDDH pin. This topology shuts off the current flowing
from VPORTP to VDDH and therefore reduces the internal power dissipation of the PD, resulting in higher overall power
efficiency.
High Power Considerations
configurations of high−power PoE systems including those
based on the developing IEEE 802.3at
operation can be enabled by a Dual Event Layer 1
classification or a Single Event Layer 1 classification
Spare
Pairs
Pairs
Data
Figure 4 shows the same non−isolated fly−back configuration as Figure 3, but adds a 12 V auxiliary bias winding on the
Figure 5 shows the NCP1081 used in a non−isolated forward topology.
The NCP1081 is designed to implement various
Spare
Pairs
Pairs
Data
RJ− 45
RJ−45
DB1
DB2
DB1
DB2
Figure 4. Non−Isolated Fly−back with Extra Winding
standard. High power
Figure 5. Non−Isolated Forward Converter
Simplified Application Diagrams
R1
R2
R2
R1
Rclass
Rinrush
Rilim1
http://onsemi.com
Rclass
Rinrush
Rilim1
TEST2
TEST1
INRUSH
VPORTN1
VPORTP
CLASS
ILIM1
UVLO
VPORTN2
TEST2
TEST1
4
INRUSH
VPORTN1
VPORTP
ILIM1
UVLO
VPORTN2
CLASS
Css Rosc
combined with a Layer 2 high power classification. The
NCP1081 also supports proprietary designs capable of
delivering 25 W to 40 W to the load in two−pair
configurations. A separate application note describes these
implementations (“NCP1081 High Power PoE Applications”).
NCP1081
Css Rosc
NCP1081
nCLASS_AT
nCLASS_AT
VDDH
GATE
ARTN
VDDL
RTN
FB
CS
C1comp
VDDH
GATE
ARTN
VDDL
RTN
C2comp
CS
FB
C1comp
Cvddh
Cvddl
Cpd
Rslope
Rcomp
C2comp
Cvddh
Cvddl
R5
Rslope
Rcomp
LD1
Rd1
Cpd
D3
LD1
Rd1
M1
Rcs
D2
T1
M1
Rcs
T1
D1
D2
D1
L1
R4
R3
R3
R4
Voutput
Cload
Voutput
Cload