The attachment is a circuit diagram drawn by my client. He wants to use 1 port , 4-pair mode. I would like to ask:
Need to use Q504, Q505 two sets of Mosfet?
Does U1's PIN48~51 need to be connected?
Is the PIN44, 45, 53, 54, 55, 56 of U1 connected to the firmware side?
Hi Hsu,
For 4 pair applications, you will need connect 2 channels with 2 sets of MOSFET and Rsense to the RJ45 connector. The connection between PSE ports and RJ45 in the above schematic is incorrect for standard PoE 4 pair application. You will need to connect channel 1 to pair 12&36 and connect channel 2 to pair 45&78. In this way, PSE can perform connection check for high power PDs and reduce 50% power losses on the cable. Please refer to TPS23881EVM-008 and BOOST-PSEMTHR-007 for reference. Channel 5-8 are designed as 4 pair ports on the EVM. Pin 48 to 51 are address pins. You can connect all to GND (address is set to 0x20 in this case) or leave them open (address is set to 0x3E in this case). Or you can do whatever combination.
This table shows the addresses related to the A1-A4 pin status.
If you plan to use autonomous mode without any host control, you can pull up RESET and INT pin to VDD. Connect 53,54 to GND and leave 55 open. Pull down 56 to GND. Thanks.
Best regards,
Penny
Hi Hsu,
Do you mean the standby power <0.21W? You can calculate the device's power consumption by using Vpwr*Ipwr+Vdd*Idd= 0.71W(max). Thanks.
Best regards,
Penny
