Si3452/3

2

Rev. 1.0

Description

When connected directly to the host system or configured in Auto mode, each Si3452/3 high-voltage port controller

provides all of the critical circuitry and sophisticated power measurement functionality for the high-voltage

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

either PoE (350 mA, 15.4 W), PoE+ (600 mA, 30 W), and extended (800 mA, 40 W) power requirements on a per-

port basis. Designed for use in Endpoint PSE (e.g., Ethernet switches) or Midspan PSE (e.g., inline power

injectors) applications, each Si3452/3 also performs the IEEE-required powered device (PD) detection,

classification, and disconnect functionality.

The flexible architecture enables powered device disconnect detection using either dc disconnect (Si3453) or

Silicon Laboratories' proprietary dV/dt disconnect (Si3452) 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 Si3452/3 from a variety of harsh surge events seen on the RJ-45 interface.

To maximize system design flexibility and minimize cost, each Si3452/3 connects directly to a system host

Functional Block Diagram

PER PORT ANALOG

HV SPI

&

Port

Control

VOUT1

Gate Control,

Current Limit

& Foldback

Detection

&

Classification

DC or

dV/dt

Disconnect

Channel

Mode

&

Limit

Control

VREF & Central Bias

PGA

DET4

VOUT2

VOUT3

DET3

DET2

Thermal

Prot.

DET1

VOUT4

Current

Sense

10b

ADC

Temp

Sensor

LV SPI

MCU Core

& PSE FSM

256 Byte SRAM

8 kByte EPROM

I2C

PLL

Voltage

Regulator

& Monitor

POR

WDT