SI3453-B01-GM Silicon Laboratories Inc, SI3453-B01-GM Datasheet - Page 14

• Manufacturer Part Number: SI3453-B01-GM
• Description: IC POE CONTROLLER MIDSPAN 40QFN
• Manufacturer: Silicon Laboratories Inc

Specifications of SI3453-B01-GM

• Package / Case: 40-QFN
• Controller Type: Power over Ethernet Controller (POE)
• Interface: I²C
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 14mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Maximum Power Dissipation: 1.2 W
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Product: Ethernet Controllers
• Standard Supported: IEEE 802.3at, IEEE 802.3af
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 3 V
• Supply Current (max): 14 mA
• Maximum Operating Temperature: + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 336-1837-5

Si3452/3
4.4. Disconnect Detection
4.4.1. dV/dt Disconnect (Si3452)
The dV/dt™ disconnect function can be used to detect a disconnected device without using dc disconnect or ac
disconnect.
In dV/dt™ disconnect mode, the FET current limit is switched to 7.5 mA. If the FET voltage increases, a load is
assumed to be present and the FET current limit is automatically switched back to its pre-selected value. If, after
350 ms, the FET voltage has not increased, there is no load present, and the FET is turned off.
In addition to operating in a manner functionally distinct from DC disconnect, dV/dt disconnect requires no
additional external components and fully interoperates with all powered device DC Maintain Power Signatures. For
more information, see "AN399: dV/dt Disconnect and the IEEE 802.3 PoE Standard".
4.4.2. DC Disconnect (Si3453)
The port current is continuously monitored by the Si3452/3. The Si3452/3 can dynamically change the
measurement scale to achieve accuracy over a wide range of currents.
As defined in the IEEE 802.3 PoE standard the PSE should disconnect if the port current is less than a nominal
7.5 mA for more than 350 ms.
4.5. Transient Voltage Surge Suppression
The Si3452/3 features robust on-chip surge protectors on each port; this is an industry first. This unique protection
circuitry acts as an active device which can withstand lightning transients as well as large ESD transient events.
When the port voltage exceeds its protection limit and the current reaches a triggering threshold, current is shunted
from the port to the ground pins.
Internal circuitry is provided to protect the line outputs from externally coupled fault currents. These are transient
currents of up to 5 A peak.
The operation of the protection circuits depends on the operating mode of the channel switch and the direction of
the fault current. The clamping operation is performed on the detect pin.
The switch itself will also be protected by the current limit. If the transient lasts long enough to heat up the die, then
the temperature sense circuit will shut off the switch, and all the fault current will flow through the clamp diode.
4.6. Temperature Sense
A temperature sense signal is used in conjunction with the current limit status signals from the gate drive blocks.
Any channel that is generating excess heat is assumed to be operating in current limit mode, with both high voltage
drop and high current.
If the port is in PoE mode, an overload will generally not result in thermal shutdown before the 60 ms I
the port is in PoE+ mode, an overload may cause the port to shut down prior to the 60 ms I
case, the event is reported as I
by the 802.3at draft and provides much more robust overload protection than is possible with external FETs.
In addition, there is a thermal shutdown if the package temperature exceeds 120 °C. If this threshold is reached, all
output drivers are turned off and detection modes are disabled. This secondary threshold limit guards against the
possibility that the overheating is not caused by a driver operating in current limit.
4.7. Port Measurement and Monitoring
VEE monitoring in conjunction with port current monitoring allows measurement of port power. Port power
monitoring, dynamic power allocation via LLDP*, and port power policing allows efficient power supply sizing.
The Si3452/3 is factory calibrated and temperature compensated for the following measurements:


*Note: LLDP = Link Layer Discovery Protocol. Refer to IEEE 802.3at (draft) and IEEE 802.1AB for more information.
14
Port current measurement. These measurements are auto ranged and scaled to a 16 bit number at 100 uA per
bit. Port current accuracy is ±4% ± 2 mA.
V
V
EE
EE
is measured with a scale of 64 V. The measurement is reported as a 16 bit number scaled at 1 mV per bit.
measurement accuracy is ±4% over the valid V
CUT
. The faster shutdown in PoE+ mode is consistent with and specifically allowed
Rev. 0.42
EE
range.
CUT
period. In either
CUT
period. If