PD671XXX-8 Datasheet, PDF (11/14 Pages) Microsemi Corporation – 24-Channel PoE AF and AT DIMM

PD671xxx - 8 / 12 / 24-Channel PoE AF and AT DIMM
Data Sheet (Non-confidential)
Enhanced Mode PD671xxx DIMM Block Diagram
Figure 8 illustrates the internal circuitry of the Enhanced Mode DIMM Master. PD69012 appears only in one of
the 12 port circuits.
Figure 8: PD67124M DIMM, Internal Block Diagram
Top Assembly Description
The following sections detail the top assembly
components.
Power Supply
The entire circuit is powered by a nominal 48 VDC
potential (Vmain can range from 44 to 57 VDC for
AF mode and 50 to 57 VDC for AT high power
mode).
3.3 VDC Regulator
Each of the PD69012 includes a 3.3 VDC regulator
(EXT_REG and 3_3Vout) for up to 6 mA. This
current is utilized for powering external components
in the PoE domain. There is an option of adding a
driver to this output to drive higher loads. Q1
provides up to 30 mA to the PoE controller and to
the opto-couplers in the interface circuit. The total
capacitance on the 3.3 VDC should be less then
4.7 uF (with and without an external driver).
Grounds
The overall circuit includes two physical ground
planes, analog and digital, which are electrically
connected at a single point on the motherboard
(see Figure 9 and Figure 10). This method, used
throughout the design, improves noise immunity
and coupling. Application note AN-132, Catalogue
Number 06-0010-080 provides further details about
this design technique.
Control Signals
Several control signals are utilized between the
switch and the PoE circuitry:
ƒ xReset_In: Driven by the switch circuitry
to reset the PoE circuit.
ƒ xDISABLE_PORTS: Driven by the
switch, to disable all PoE ports
immediately.
Indication Signals
ƒ Int_out: Enables the Host CPU to
reduce the communication volume
whenever a PoE event masked by the
Host CPU occurs. The PoE Controller
sends an interrupt for indication.
ƒ System_ok: (Enhanced mode only) An
optional hardware single line, driven by
the Master DIMM to the Host CPU; this
signal provides the Host CPU with a
warning that a major failure such as
Vmain out of range has occurred.
Copyright © 2009
Microsemi
Page 10
Rev. 1.0 / 17-March-10
Analog Mixed Signal Group
2381 Morse Avenue, Irvine, CA 92614, USA; Within the USA: [phone], Outside the USA: [phone] Fax: [phone]