SI3482-A01-GM Silicon Laboratories Inc, SI3482-A01-GM Datasheet - Page 7

• 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
Figure 4. Grant Based Power Management
Figure 5. Consumption-Based Power Management
If the granting policy is grant based, then the power remaining for new grants is the total ungranted power. The
power remaining is the total power provided minus the total power granted.
The problem with this approach is that much of the provided power is unused because PDs often do not consume
all of their granted power.
If the granting policy is consumption-based, then the power remaining for new grants is the total unconsumed
power. The power remaining is the total power provided minus the total power consumed (excluding the reserved
power). This approach uses more of the provided power, but there is a possibility that the system may consume
more power than the power provided (system overload).
To avoid system overloads caused by momentary surges in power consumption, the host can specify that a certain
amount of power be held in reserve. The Si3482 does not use the reserved power when granting new requests.
Most power supplies can tolerate a limited amount of overload for a short duration. The host specifies the overload
limit of the power supplies to the Si3482. If a system overload is less than the overload limit, the Si3482 turns off
ports, one at a time in priority order, until the system is no longer overloaded. If a system overload is greater than
the overload limit (severe overload), the Si3482 immediately turns off all low-priority ports. If the system is still
overloaded, the Si3482 turns off additional ports, one at a time in priority order, until the system is no longer
overloaded. A severe overload is usually caused by removing a power supply.
2.1. Host Interface
The Si3482 has a UART interface and an SPI interface for communicating with the host MCU, but only one
interface is used at a time. The PSLCT (protocol select) pin selects which interface is used.
2.1.1. UART Interface
If the PSLCT pin is tied high, then the Si3482 uses the UART interface to communicate with the host MCU. The
Si3482 uses the TX and RX pins to send and receive serial data. The BAUD0, BAUD1, and BAUD2 pins select the
baud rate for the UART interface.
Rev. 0.1
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