I am designing a flow transmitter with Power over Ethernet(PoE) output. I am assuming the power consumption of the device is going to be low (< 11 Watts) for which power demand fall under 802.3at standard.
Now, the customer is demanding flow transmitter's supply designed to be compliant with 802.3bt (class 4, single signature) standard. I am well aware that PSEs are backward compatible.
My doubt is, If I design transmitter's power supply 802.3bt compliant (which is for high power PDs) and if the total power consumption in run mode to be (let's say) 5 watts, will there be any problem in operation?
The reference design I am using https://www.ti.com/lit/ug/slvub75a/slvub75a.pdf. which is based on TPS2372-4 interface IC.
If any further detail required to answer, please let me know.
The PSE type and highest class defines the upper limit of its power supply, it's your choice.
See 802.3bt Clause 145.2.1 - a bt-compliant PSE is either type 3 or 4. It can be limited to any power class, from 1 through 8.
So, a 5 W PSE can only supply class 1 PDs.