SI3482-A01-GM Silicon Laboratories Inc, SI3482-A01-GM Datasheet - Page 6

• Manufacturer Part Number: SI3482-A01-GM
• Description: IC CTLR POE 24-48PORT PSE 24-QFN
• Manufacturer: Silicon Laboratories Inc

Specifications of SI3482-A01-GM

• Applications: Power Over Ethernet Controller
• Current - Supply: 12.1mA
• Voltage - Supply: 2.7 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-WFQFN Exposed Pad
• Product: Power Distribution
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Si3482
2. Functional Description
The Si3482 Power Management Controller is the central controller in a Silicon Labs Power over Ethernet (PoE)
system. In a PoE system, power is provided by one or more power supplies and is consumed by one or more
powered devices (PDs). The Si3482 decides which of the PDs can have power and monitors the amount of power
consumed by each.
A host microcontroller unit (MCU) can configure the Si3482 and can query the status of the PDs and the power
supplies. The Si3482 stores its configuration in internal flash memory. A host MCU uses a Universal Asynchronous
Receiver Transmitter (UART) or a Serial Peripheral Interface (SPI) to communicate with the Si3482. Pins on the
Si3482 select which host interface to use and which baud rate to use for the UART interface.
Power supplies may be inserted into bays. The Si3482 supports a system with up to three bays. Power supplies
may be inserted or removed from the bays at any time. Each bay provides a signal to the Si3482 that indicates if a
power supply is present in the bay. The outputs of the power supplies are ganged together to provide a single
power source for the system.
The Si3482 manages a collection of Si3452 Port Controllers. The Si3482 supports a system with up to 12 Si3452s.
Each Si3452 has four ports; so, a system may have up to 48 ports. The Si3452 performs low-level port functions,
such as detecting and classifying PDs. The Si3482 has a global view of the system and manages power across all
ports.
PDs are connected to ports on the Si3452s. PDs may be connected or disconnected from the ports at any time.
When a PD is connected to a port, then the PD requests power from the port. The Si3482 determines the amount
of power requested from the classification of the PD. If there is enough power remaining, the Si3482 grants the
request; otherwise, the Si3482 denies the request.
The host may configure an optional power limit for each port. A power limit restricts the amount of power that the
Si3482 grants to a port. If a power request is greater than the power limit, the Si3482 does not fully grant the
request, but only grants the amount of the power limit.
The Si3482 supports Link Layer Discovery Protocol (LLDP) agents in the host. An LLDP agent can call a routine in
the Si3482 to dynamically adjust the amount of power granted to a PD during the course of a connection.
Several PDs may be connected to a PoE system. The Si3482 may have granted different amounts of power to
each PD, and each PD may be consuming different amounts of power. If a PD consumes more power than it is
granted (port overload), the Si3482 turns off the PD.
There are two approaches that the Si3482 can take when granting requests for power. The granting policy can be
grant-based or it can be consumption-based.
Figure 3. Powered Devices Example
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