TPS23753: adding ON/OFF switch to controll power tern on

Ajay Kumar55

Part Number: TPS23753

Hi,

I want to design a ethernet switch and it will be powered from PoE PD as well as external adapter. I want to controll the power on from ON/OFF switch. if ON my circuit should power on from PoE or adapter. when OFF circuit shpould not turn on fron either Poe or adapter. is it ok to connect a switch between DEN pin and DEN resistor, where DEN resistor is connected to VDD.

over 7 years ago

0 Darwin Fernandez over 7 years ago

TI__Mastermind 41770 points

Hi Ajay,

Yes you can use a circuit around the DEN pin to remove power from PoE and corrupt detection so that the PSE does not try to reconnect. I recommend using the circuit on Figure 10 from the app note below to do this.

www.ti.com/.../slva306a.pdf

Please let me know if this helps. Thanks!

Regards,
Darwin

0 Ajay Kumar55 over 7 years ago in reply to Darwin Fernandez

Prodigy 200 points

Hi,

I want to use switch so when switch in in 1-2 position PoE controller should not turn on. when switch is in 1-3 position PoE controller should take power from PoE or adapter. please let me know if below circuit is ok and will work or not?

0 Darwin Fernandez over 7 years ago in reply to Ajay Kumar55

TI__Mastermind 41770 points

Hi Ajay,

The solution above will only work if PoE has not been connected yet. If PoE is already powering the load, and the switch gets opened, there will be no guarantee that the PSE will remove power because the PD pass FET will not open consistently because the DEN pin is floating.

I recommend what we originally suggested. The BJT can be replaced with a toggle switch.

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TPS23753: adding ON/OFF switch to controll power tern on