# T2P, Power Demotion, SG, Ideal diode bridge in DC2476A-A

To whom may it concern.

Hi I'm HS.

I have DC2476A-A and want to use T2P as type indicator via LEDs, which means I want to use 3 LEDs so that they indicate 4 states: af, at, bt(around 61W), bt(around 71W)

I set the output as 28V.

If I attach the LEDs to the secondary part of octo-coupler, LEDs will be oscillating from V_OUT=28V to 0V so it may make users frowned upon or seem to be stagnant since Pin T2P throw pulses out to octo-coupler at 976Hz.

So my question is...

1. What would be the most effective way to indicate 4 states using LEDs?

2. Is there any specific action when PD is demoted so that you can tell it is demoted or just normal operation.

ex) Datasheet said, 50% 976hz pulse means 51W --> Class 6.

How do you know if it's normal operation(class 6 by itself) or it is demoted?

3.

3-1. I want to change the voltage level of the T2P pulse cuz it's too high(Since V_OUT=28V) to connect to LEDs

Would it be ok if I pull-up to other voltage values, somewhat lower than V_OUT(=24V)?

Or How can I lower the voltage value in addition to connecting resistors in series with pull-up resistors?

3-2. I think i may attach LC filter to T2P so that it alters pulse into a smoothly-filtered continuous voltage waveform, DC. 3 comparators which are made of op-amps will be placed next to the LC filter. I hope the output of comparators is around 1.8V. I think I draw 1.8V from somewhere, idk..maybe voltage regulator from 7805 or something, and connect it to VDD of comparator.

Do you think it's a good idea to discern the state of PD(af,at,bt) and send this data/signal to end- device??

3-2-2. Comparator's VCC and V_REFs will be given/divided by V_OUT. V_REF will be referenced from V_OUT via 5.1V Zener Diode. Do you think it's a good way to get VCC from secondary area?

4.

4-1. What's the purpose of R13, C17 on the primary side of T3 and C20, D13, R18, R15 on the secondary side?

4-2. Reference schematic put  zener diode, D17(PMEG1020EA) at Pin PG , but no zener at Pin SG. What's the difference??

4-3. Reference schematic put gate driver at secondary power MOSFET but nothing at primary power MOSFET. What's the difference??

4-4 Why does gate driver need Transformer(T3)?, Why didn't reference design connect gate driver to Pin SG directly??

5. In reference schematic, Output filter has R35(Opt). What effect can we expect if we insert this R35? Any voltage drop? Higher filter performance??

6. In reference schematic, R5(8.2Ohm) is connected to Pin VPORT in LT4295. What's the purpose of this R5?

7. This is the screenshot of PoE ideal MOSFET Diode Bridge using LT4321 in DC2476A-A

What's the purpose of R28, D2, D3 and C11??

8. Layout.

I couldn't find any information/tips for layout of DC2476A-A.

Is there anything that i have to know and take care of when it comes to layout??

I think you guys use 6 layers PCB.

What's the impedance of pcb and what width should i use for line and data??

Thank you for your hard work and I appreciate it a lot

Hope you have a good day

Added layout
[edited by: feelyoursoul at 12:26 AM (GMT 0) on 26 Nov 2019]