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10.3.2 Silicon Labs Si3452 Quad High Voltage Port Controller for PoE + PSE

When connected directly to the host system or configured in Auto mode, each Si3452 high-voltage port

controller provides all of the critical circuitry and sophisticated power measurement functionality for the

high-voltage interfaces of four complete PSE ports. The Si3452 fully integrates robust, low-R

(0.3Ω

typical) power MOSFET switches, low-power dissipation current sensing circuitry, and transient voltage

surge suppression devices. The on-chip current sense circuitry and power MOSFETs provide

programmable scaling of current limits to match PoE (350 mA, 15.4 W for 2 ports) and PoE+ (600 mA, 30

W for one port) power requirements on a per port basis. Each Si3452 also performs the IEEE-required

powered device (PD) detection, classification, and disconnect functionality.

The flexible architecture enables powered device disconnect detection using Silicon Laboratories

proprietary dV/dt disconnect sensing algorithm. dV/dt disconnect is an alternative to DC disconnect that

requires no additional BOM components, does not dissipate extra device power, and fully interoperates

with all powered devices. Also provided are multi-point detection algorithms and per-port current and

voltage monitoring.

Intelligent protection circuitry includes power supply under voltage lockout (UVLO), port output current

limiting and short-circuit protection, thermal overload sensing and port shutdown, and transient voltage

surge suppressors capable of protecting the Si3452 from a variety of harsh surge events seen on the RJ-

45 interface.

To maximize system design flexibility and minimize cost, each Si3452 connects directly to a system host

controller through an I2C serial interface.

Figure 31 – Silicon Labs Si3452 functional block diagram

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