ncp1083 ON Semiconductor, ncp1083 Datasheet - Page 12

• Manufacturer Part Number: ncp1083
• Description: Integrated High Power Poe-pd Interface & Dc-dc Converter Controller With 9v Auxiliary Supply Support
• Manufacturer: ON Semiconductor

PSE Type identification:
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 NCP1083 DC-DC converter, the nCLASS_AT pin will
be pulled down to ARTN by the internal low voltage NMOS
switch (ARTN is the ground connection of the DC-DC
converter and completes initialization, the microprocessor
should check if the NCP1083 detected a two event hardware
classification by reading its digital input (pin IN1 in this
example). If pin IN1 is low, the application knows power is
supplied by a draft IEEE 802.3at (D3.0) compliant PSE, and
Number of Mark Event:
The nCLASS_AT active low open drain output pin can be
As soon as the application is powered by the DC-DC
Operation Mode:
Reset Range
Mark Range
Class range
Figure 10. Isolated nClass_AT Communication with the Powered Device Application
20.5 V
13 V
9.7 V
5.4 V
0 V
Detection
X
Figure 9. Hardware Physical Classification Event Sequence
PSE identified by default as type 1 PSE (af)
1st Class Event
0
http://onsemi.com
1st Mark Event
with Mark Events (.at spec)
2 Fingers Classification
12
converter). Otherwise, nCLASS_AT will be disabled and
will be pulled up to VDDL (3.3 V 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.
can deliver power up to the level specified by the draft IEEE
802.3at (D3.0) standard.
classification with the PSE. There are several scenarios for
which the NCP1083 will not enable its nCLASS_AT pin:
•
The following scheme illustrates how the nCLASS_AT
Otherwise the application will have to perform a Layer 2
The PSE skipped the classification phase.
1
2nd Class Event
2nd Mark Event
PSE identified as type 2 PSE (at)
UVLO_on
2
Power On