PD64012

12-CHANNEL PoE MANAGER

Macros (802.3 Standard)

Classification – upon request from the MCU, a state machine applies a regulated 18 V on the port output. The

internal current is measured by a metering circuit, compared with a number of preset ranges and in this manner,

the classification is established.

Line Detection – the MCU generates a request to have four separate voltage levels applied to the output port. A

unique measurement circuit monitors the delta between the second and third levels, and between the third and

fourth levels. The voltage differences are compared with values stored in registers. By comparing the values, the

system can decide whether or not to enable the port.

AC Disconnect – the system applies a sinusoidal signal to the positive terminal of the port. The voltage developed

on the port terminals is proportional to the value of the load. If the load is high, the AC component riding on the port

terminals, will be small and reversed. If the load low, the AC component will be large. A special circuit measures

the level of the AC component and compares it with a value stored in a register. Based on the comparison results,

the system decides to disable the port or not.

DC Disconnect for DC Modulation: senses if the port current falls below 7.5 mA. If so, a flag is raised and timers in

the Channel RT Controller are enabled. The Channel RT Controller acts according to pre-programmed limits for

thresholds and time windows, prior to initiating a disconnect status for that port. The circuitry takes into account

PD’s that modulate their current consumption, disconnecting them only if necessary.

Analog Section

Clock Oscillator

A 4 MHz oscillator, used for internal logic and timers.

Power on Reset (POR)

Monitors the internal regulated +3.3 V and generates a Reset signal, if this value drops below 2.8 V. The Reset

signal resets the ASIC’s logic and generates an output flag to the other PD64012 ASICs, via the RESET_N pin.

Charge Pump

This circuit block generates a voltage which increases the main input voltage by 10 VDC (approx.). This potential

is used to operate the AC Disconnect circuits.

Current Limit

This circuit continuously checks the current for enabled ports. Once the current exceeds a specific level, the

system starts to measure the elapsed time. If this period is greater than a preset threshold, the port is disabled. In

all cases, the output current will not exceed a pre-established maximum.

Real Time Protection

This circuit receives flags from two locations in the PD64012: from the sense resistor and from the main input

voltage (48 V). A 10-bit A/D Converter feeds the Digital section, at the Current and AC Voltage Measurement block.

From there on, the system handles the levels according to pre-programmed limits.

DC Disconnect Comparator

Once the port current drops below a set limit, the comparator provides an indication to the DC Disconnect Logic to

that effect.

PD-IM-7348 Evaluation Board

The performance features of the PD64012 PoE Manager can be fully appreciated with the PD-IM-7348 Evaluation

Board. This board allows to investigate all functions accessible to the designer. The evaluation board supports up

to 48 ports, has both I

www.powerdsine.com

© PowerDsine 2003

Information in this document subject

06-0003-058 (Rev. 2.8) / 5 August 2004

to change without prior notice.

10