TPS2121: Output Not Present.

Hi Arsalan,

Where are you probing this 3-4V output? It is before or after the resistor on R25?

Can you please share some scope shots of this phenomenon?

I would like to see PR1, CP2, VOUT and if possible IOUT.

If you have an external 5V or 3.3V rail. ST can be pulled up to it (though a resistor) and be used as a diagnostic aid which lets you know which channel is selected.

Hello,

Here is my setup IN1 = 12V, IN2 = open

The values are

PR1 = 2.6V

CP2 = 0V

Vout = 0.1-0.3V fluctuating. before R25.

These measurements are taken using Voltmeter.

I cannot pull up the ST pin as It's connected to GND through via on the board.

Hello,

While Testing I just encountered a weird test case.

When I reduce the IN1 voltage to 9V then Vout becomes valid and then it stays valid in the whole range. What is this behavior. Can you explain ? 

What is the voltage on OV1 when you use 12V on IN1?

By the way leave IN2 disconnected.

Voltage on OV1 is 0.88V.

Yes It's disconnected.

Hi Arsalan,

The reported figures are inconsistent with the expected behavior from the device.

To further support this, we would like some scope shots with just IN1 being used and IN2 disconnected.

For this scopeshot we would like to see IN1, PR1, VOUT and IOUT.

The test would be a the turn on event (when IN1 is applied).

Hello,

Yes I know that these figures that I gave are inconsistent with the expected behavior that's why I asked this question and confused why it's happening this way. 

I do not have scope at the moment. I'll get back to you when I have it with me. 

Meanwhile, I have removed the Css and now Vout is 12V if I connect 12V to IN1 or IN2.

For Test Purposes I have changed the Css with 10uF, 3uF, 0.22uF but no Success.

Hello,

Sorry for the delayed reply. I was away.

I have now oscilloscope in hand but now the board is working fine. I have removed the SS cap from the circuit but I cannot work on board now as it is not with me. 

Thanks for the assistance. I'll experiment on it when I get it.