TPS2121: Vout is turn on/turn off repeat

Amos Chen

Part Number: TPS2121

Hi Sirs,

Would you help recheck the TPS2121 schematic? The Vout is turn on/off repeat.

I measured the I_VIN2 (12V input current) is about 1.3A.

1, VIN1 is not valid (no connect) and VIN2 is vaild (connect to 12Vin)

2. Both PR1, CP2 are low.

3. Does the Vout off due to SS?

I want TPS2121 to function as the follows:

1. When IN2 voltage is valid only (IN1 is not valid), OUT voltage is IN2 any time.

2. When both IN1 and IN2 voltage are valid, OUT voltage is IN1 any time.

Thank you

Amos.

0 Shreyas Dmello over 4 years ago

Hi Amos,

It looks like the device is hitting a fault and restarting every 25ms. This could be a current limit or thermal fault.

When IN2 turns off, I see that the output is at 5V. Why is this the case if IN1 is disconnected? What is the load here?

Secondly, what is the total output capacitance for tis device?

Can you please provide a waveform with IN2, CP2, IOUT and VOUT probed? Could you also make sure that the Rilim is correctly set.

0 Amos Chen over 4 years ago in reply to Shreyas Dmello

Hi Sir,

The issue is been solved. Seems TPS2121 restarting due to OC protection, we found the load device is polarity reversed.

Thank you for the feedback,

Amos.

0 Shreyas Dmello over 4 years ago in reply to Amos Chen

Hi Amos.

Thanks for following up on this. I will close out the thread.

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