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TPS2373: SPEC Question

Kai Hsiao
Guru 12675 points
Part Number: TPS2373
Other Parts Discussed in Thread: TPS2372

HI Sir 

I have some question of TPS2373 

1. Do you have 6.25ohm cable's brand and datasheet ?? due to type 4 need 6.25ohm  Ethernet cable 

2. AC impedance lower than 26.3 kΩ in parallel with 0.05 μF for MPS function ,May I know which schematic have these cap and resistor ?

3. I saw "10- mA pulsed current for at least 75 ms every 325 ms" for 802.3at in datasheet ,but below figure show 300mS and 60mS ,is it correct ?

4. I saw "for Class 5-8 PDs have also increased to 16 mA at the PSE end of the ethernet cable" in datasheet ,but below figure show 14mA ,is it correct ?

5. Can TPS2373 support Dual Signature PD Structure?

6. About Autoclass ,how PSE can know the max power of PD? Measure Voltage or current ??

  • 0
    TI__Genius 9230 points

    Answer:
    Hi Kai,

    1. 6.25 ohm comes from using 4 pairs of (25 ohm/pair) Cat5e ethernet cable for power instead of 2 pairs with .at (12.5ohm total). Using a Cat5e cable or greater will be sufficient.

    3/4. The figure does not reflect the .bt standard. The 320 ms, 6ms, and 16mA values you are mentioning are correct. I would not go with this figure if it was not found on the datasheet.

    6. See the datasheet for TPS2372 for more information on autoclass. (not supported inTPS2373)
    www.ti.com/.../tps2372.pdf

    2 & 5. Let be get back to you on those.

    - Thomas A.

  • 0 in reply to Thomas Amlee
    TI__Genius 9230 points
    2. All of our EVMs & TI Designs should meet this requirement. Just make sure to keep your input capacitor (across Vdd-Vss) less than 0.12uF.

    5. TPS2373 does support Dual signature, however this is a feature that is designed at the board level. The IC itself does not prevent or allow its implementation. One note: you must change your class resistors if you choose to do dual signature. I'll reply with a table of the values.

    - Tom A.
  • 0 in reply to Thomas Amlee
    TI__Genius 9230 points

    Notice that 4 class fingers are seen with different current levels than with a typical single PD implementation.