NCP1080

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3

Simplified Application Diagrams

LD1

Rd1

NCP1080

Data

Pairs

Spare

Pairs

Rcs

Cvddh

Cpd

Css

Rosc

M1

T1

Cload

Rclass

Rilim1

Rinrush

R1

R2

Optocoupler

R3

R4

R5

C1

Z1

Rslope

C2

Voutput

RJ−45

D1

DB1

DB2

OC1

GATE

RTN

FB

VPORTN2

VDDH

VDDL

VPORTN1

CLASS

ARTN

ILIM1

INRUSH

TEST1

TEST2

UVLO

CS

VPORTP

Cvddl

Figure 2. Isolated Fly−back Converter

Figure 2 shows the integrated PoE−PD switch and DC−DC controller configured to work in a fully isolated application. The

output voltage regulation is accomplished with an external opto−coupler and a shunt regulator (Z1).

NCP1080

GATE

RTN

FB

VPORTN2

VDDH

VDDL

Rcs

Cvddh

Cpd

C1comp

C2comp

Rcomp

Css Rosc

M1

T1

Cload

R3

R4

VPORTN1

CLASS

ARTN

ILIM1

INRUSH

TEST1

TEST2

Rclass

Rilim1

Rinrush

UVLO

CS

VPORTP

Rslope

Voutput

Data

Pairs

Spare

Pairs

R1

R2

RJ−45

DB1

DB2

LD1

Rd1

Cvddl

Figure 3. Non−Isolated Fly−back Converter

Figure 3 shows the integrated PoE−PD and DC−DC controller configured in a non−isolated fly−back configuration. A

compensation network is inserted between the FB and the COMP pin for overall stability of the feedback loop.