TPS54240: TPS54240 EN pin off output problem

Hi Kevin,

Is the supply connected to any load? Assuming you are powering up the board and then pulling the EN low. The output voltage will discharge slowly from the output capacitor and feedback resistor dividers.

Thanks,

Ethan

Hi Ethan

The output will have voltage 1.8V, both loaded and unloaded.
Now I have to turn off via MOSFET switch before the on Vin, is this normal? Does the TPS54240 have this phenomenon?

Sincerely

Kevin

Hi Kevin, 

Are you saying you are using Q821 to turn off the device so that 1.8V will fall and then power again? Are you testing this across multiple units?

Can you provide waveforms of start-up, power-down, and some waveforms of the issue you are dealing with (no load and with load). Please provide Vin,Vout, EN and SW.

Thanks,

Ethan

Hi Ethan,

Yes, using Q821 to turn off the device output ,so output has no voltage output.

Output has no voltage output, Otherwise, according to here circuit, when EN is off, the output will have 1.8v output.

Sincerely

Kevin