TPS23751 MAXIMUM OUTPUT POWER FOR PD

You will need a solution similar to www.ti.com/.../universalsearch.tsp;src=top

Hi Eric,
Thanks for your help. But why this solution is non-standard?. What does it means? Is it not compliant with the standard IEEE802.3at?
Regards
Javier

The present standard covers PD's up to 25.5W over 2 pairs. There is ongoing committee work for the new standard for power over 4 pairs with much higher power levels but that is not "official" yet. There is Cisco UPOE which is an extension of the .at standard over 4 pairs which is closest to "official". This simply doubles the 25.5W to the PD using two .at ports over a single cable. You can find out more in www.ti.com/.../litabsmultiplefilelist.tsp;docCategoryId=1&familyId=664&keyMatch=slva625&tisearch=Search-EN-Everything

Hi,
So 25.5W is the maximum power to compliant with the standard?. Because I have seen some companies like Linear technology or Microsemy which have PD controllers which support up to 95W and they are compatible to IEEE 802.3 standard. Here

file:///C:/Users/Javier/Downloads/PoE_ICs_product_brief_Feb_2013.pdf

www.linear.com/.../LT4275

So what about these products from these companies?. They are compatible with the standard IEEE 802.3?

The LTC and Microsemi devices are compliant with IEEE 802.3at, but their high power-4 pair schemes (LTPoE++ for example) are not. This means that there is no interoperability between PSE-PD vendors for any current non-standard high power scheme. At present, there is no IEEE standard for high power but there will be a unified approach in the future.

TI also has a non-standard, 4-pair high power approach using the TPS23861 and TPS2379 based PD. Or, TPS23861 and the dual TPS2378 design for UPOE described in the SLVA625 application report.

You can find the latest IEEE 802.3 standard below. There are 6 sections, the PoE is in section 2

http://standards.ieee.org/getieee802/download/802.3-2012.zip

 

Ok, so If I understand correctly, if I use a non-standard high power PD vendor, the PSE has to be also from the same vendor for interoperability right?.
In my case the PD includes a single board computer (7W), one camera (4W), WIFI module(low power), RFID reader(10W) and one light (2W).
So if I use the TPS2379 to power these devices. Will it work with a standard PoE injector? or I will have to choose one PoE injector that can deliver more power?. If so, it would be compatible with the TPS2379?

Generally speaking, yes for > 51W at the PD using 4-pairs the PSE-PD supplier would be the same. For PD power between 25.5W and 51W, UPOE is somewhat more inter-operable as it is really just an extension of IEEE 802.3at over 4 pairs (2x type 2 .at power levels).

TPS2379 is an IEEE 802.3at compatible type 2 PD controller that can be used with the external FET to boost the current above 25.5W. It will work fine with POE injectors.

Ok so in my case, my application the PD need around 40W in order to work properly, so the TPS2379 would be fine right?. But in this case the TPS2379 would be a non-standard application right?. So will it work with all kind of PoE injectors which can deliver more than 40W (standard and non-standard)?.
And another question, what is the problem when an application is non-standardad?

Phihong has several 4-pair injectors that will work fine with the TPS2379 (and TPS2379EVM-106). For example, POE60U-560(G) -R is a 60W injector that just looks for a 12.5kohm detection signature. The TPS2379EVM-106 has an onboard jumper which can be configured to present the 12.5kohm detection resistance and as such will be powered over 4 pairs by the POE60U-560(G) -R.

And if I configure the TPS2379 to present the 24.9Kohm detection signature, instead of the 12.5Kohm . Then, the maximum power that the TPS2379 can draw is 25.5w (regarding the standard)??, even if the PoE injector can deliver more than this power??.
And for high power, only the Phihong PoE injectors would work with the TPS2379?. Or I just need to know which detection signature looks for the PoE injector in order to put the same detection signature in the TPS2379?.

Hi Javi,

Let's say you use the TPS2379EVM (capable of 2A high power as is). If you use the higher power Phihong capable providing 25W power if presented with 25k detection resistor or higher power with 12.5k detection resistor, the TPS2379EVM will be capable to providing 25.5W delievered to the PD with a 25k detection resistor (with Class 4 resistor) and will be capable of providing higher power delivered to the PD with 12.5k resistor. 

The PSE will limit it's power delievered based on what the PD 'tells' the PSE it can provide.