We design POE++ with LTC4266A-3 , but now the output can be only around 30w with 90w PD (LT4275), can you kindly help to advice,
1. How can i get the software programming documentation.
2. Things to improve with the design...
The LTC4266A-3 in AUTO pin high mode outputs up to the LTPoE++ 70W power level. If you are trying to achieve LTPoE++ 90W power, use the LTC4266A-4. Make sure the LT4275 classification resistors are set for the required power level.
1) Please contact you local ADI sales office to obtain this document.
2) On the schematic portion you provided, I have the following comments:
- At each port output, change the 0.47uF,100V capacitors (C40-C43) to 0.22uF, X7R, 100V.
- Make sure a bulk TVS and bulk capacitance (not shown) is across -55V_RTN and -55V power supply.
- For the LTPoE++ 70W power level, I recommend using the PSMN040-100MSE MOSFET instead of the PHT6NQ10T for a lower RDSON and high SOA MOSFET.
- Make sure the PSE Ethernet transformers (not shown) are rated for the LTPoE++ 70W current levels.
When operating in AUTO pin high mode, the LTC4266A-3 will power a PD at each port requesting up to the LTPoE++ 70W level. At each port an IEEE Type 1, IEEE Type 2, LTPoE++ 38.7W, LTPoE++ 52.7W, and LTPoE++ 70W PSE PD will be powered. An LTPoE++ 90W PD will be denied power with this power grade version of the LTC4266A.
Further power management functionality can be performed via I2C outside of auto mode.
Good day, thank you for the support before. After checking we find it seems is caused by fail to access to Auto mode.
So we change to manual mode and modify the Ilim setting, it work.
Seems we still have problem with choosing working mode, but the whole design follows DC1815A-C.