Copyright © 2013 Microsemi
Rev. 1.7, 17-July-2013 Analog Mixed Signal Group
1 Enterprise, Aliso Viejo, CA 92656, USA; Phone (USA): (800) 713-4113, (ROW): (949) 221-7100 Fax: (949) 756-0308
1 Port PSE PoE PD69101 Controller
Theory of Operation
The PD69101 performs IEEE802.3af, IEEE802.3at
functionality as well as legacy (capacitor) and Cisco’s
PDs detection, as well as additional protections such
as short circuit and dV/dT protection upon startup.
Line Detection
The Line Detection feature detects a valid AF or AT
load, as specified in the AF / AT standard. Resistor
value should range from 19 kΩ to 26.5 kΩ. Line
detection is based on four different voltage levels
generated over the PD (the load) as illustrated in
Figure 2.
v
t
2 Events
Classification Phase
Detection
Phase
Start-Up
(Inrush)
Power
“ON”
Power
“OFF”
Figure 2: Typical PoE Voltage Time Diagram
Legacy (Cap) Detection
In cases where pin 24 (LEGACY) is set to “0”, the
PD69101's detection mechanism is configured to
detect and power up LEGACY PDs, as well as AF/AT
compliant PDs.
This mechanism detects and powers up CISCO Legacy
PDs as well.
Classification
The classification process takes place right after the
resistor detection, when the resistor detection has
completed successfully. The main goal of the
classification process is to detect the PD class, as
specified in the IEEE802.3AF and AT standards.
In the AF mode the classification mechanism is based
on a single voltage level (single finger).
In the AT mode classification mechanism is based on
two voltage levels (dual finger) as defined in the
IEEE802.3at-2009.
Port Start Up
Upon a successful Detection and Classification
process, power is applied to the load via a controlled
Start Up mechanism.
During this period current is limited to 425 mA for a
typical duration of 65 mS, which enables the PD load to
charge and to enter a steady state power condition.
Over-Load Detection and Port Shut Down
After power up, the PD69101 automatically initializes
its internal protection mechanisms utilized to monitor
and disconnect power from the load in cases where
extreme conditions such as over-current or short ports
terminals scenario occur, as specified in the
IEEE802.3AF/AT standard.
Disconnect Detection
The PD69101 supports DC Disconnect function as per
the IEEE802.3AF/AT standard.
This mechanism continuously monitors load current
and disconnects power in cases where load current is
below 7.5 mA (typ.) for more than 322 mS.
Over-temperature Protection
The PD69101 has internal temperature sensors that
continuously monitor junction temperature and
disconnect load power when the junction temperature
exceeds 200° C. This mechanism protects the device
from extreme events, such as high ambient
