ncp1081 ON Semiconductor, ncp1081 Datasheet - Page 12

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

IEEE802.3at (D3.0) compliant may apply more than two
fingers, but the final result will be the same as two fingers).
nCLASS_AT Indicator
used to notify to the microprocessor of the powered device
that the PSE performed a one or two event hardware
classification. If a two event hardware classification has
occured and once the PD application is supplied power by
the NCP1081 DC−DC converter, the nCLASS_AT pin will
be pulled down to ARTN by the internal low voltage NMOS
The nCLASS_AT active low open drain output pin can be
PSE Type identification:
Operation Mode:
Number of Mark Event:
Reset Range
Mark Range
Class range
Class_AT
Figure 8. Isolated nClass_AT Communication with the Powered Device Application
NCP1081
VDDL
Detection
20.5 V
13 V
9.5 V
5.4 V
0 V
20uA
X
Figure 7. Hardware Physical Classification Event Sequence
PSE identified by default as type 1 PSE (af)
1st Class Event
0
ARTN
nCLASS_AT
VDDL
1st Mark Event 2nd Class Event
http://onsemi.com
2 Fingers Classification with
Rled
Mark Events (.at spec)
(Isolated DC/DC converter)
12
Opto 1
Isolation
switch (ARTN is the ground connection of the DC−DC
converter). Otherwise, nCLASS_AT will be disabled and
will be pulled up to VDDL (3.3V typ) via an internal current
source (20 mA typ) and via the external pull−up resistor.
pin may be configured with the processor of the powered
device. An opto−coupler is used to guarantee full isolation
between the Ethernet cable and the application.
1
The following scheme illustrates how the nCLASS_AT
Rbip
Csup
2nd Mark Event
Powered Device Application
PSE identified as type 2 PSE (at)
IN2
IN1
UVLO_on
GND
VSUP
2
Microprocessor
Microcontroller
Power On
Features
Layer 2
Engine
or