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Part Number: INA285
Below is my customer design concern.
He applied INA285 in each RJ45 data pair.
As below picture, he use INA285 on pin 1, 3, 5, and 7.
And for these pins, they use below circuit on it.
However, after applied INA285, all 4 pairs had cross-influence with each other.
As I know for INAxxx porduct, they are major for current measure for power trace, not for data trace, right?
If it also can use on data trace, could you help to give me some advise for customer issue and some design suggestion.
Patrick Simmons, TI Sensing Products Applications Support
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In reply to Patrick Simmons:
Yes! Below is my customer NEXT test (Near End crosstalk Test) result!
It can be see that after add INA285, the signal low than 50MHz will be influenced.
As customer RJ45 support PoE function, that means common mode voltage should be more than 48V, and they hope the G>=500!
Therefore, is there any other solution suitable for my customer if INA285 cannot use for such design?
BTW, current shunt product also can design for data signal measurement?
In reply to Peter Tseng:
You may be able to use a fully differential amplifier such as the THS4541 to amplify the signal. What is the value of the shunt resistor, what is the current expected through the shunt resistor, and what voltage is needed at the output?
Jacob Freet High Speed Amplifiers
In reply to Jacob%20Freet:
As customer information, the Rsense they will use 2mohm, and the current will be 1~2A on the power rail.
For voltage, since the application is POE related, they will need up to 48V POE power for current shunt design.
Thank you for the information. CAn you clarify what you mean when you say they will "need up to 48V POE power"? Do you mean that the amplifier must be powered off of 48V or that the voltage at the shunt is 48V?
As my attached pictures and description above, customer use current shunt in pin1,3,5, and pin7 of RJ45 connector.
Due to their application is PoE related product and the PoE voltage must be carry via data pairs from PSE to PD.
The current shunt will face the 48V high voltage from PSE.
That's what I mean.
If my understanding is wrong, just feel free to correct me.
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