TPS22965: Non functioning of TPS22965NQWDSGRQ1 load switch

Hi Devendhiran,

Thanks for reaching out on E2E!

At an initial glance, I don't see anything wrong with the schematic.

Can you answer the following questions regarding the device and the application?
1. Have you tried disconnecting the downstream load and testing the TPS22965 by itself? What is the downstream load?
2. Can you share any oscilloscope shots?
3. When does the device fail? During startup? During normal operating conditions?
4. Does replacing the device fix the issue such that the circuit operates normally?
5. Is this a prototype or production platform?
6. What is your thermal pad connected to, GND?

Thanks,

Arthur Huang

Hi Arthur Huang,

Thanks for the reply.

1. Have you tried disconnecting the downstream load and testing the TPS22965 by itself? What is the downstream load? 

Response : 

We have disconnected the load on 3V3 load switch (U202) and verified that still CT voltage is not generated and the Input voltage is not switched to the output. 

Not disconnected the load and verified the functionality for the 1V8 load switch (U203).

SoC and its associated peripherals (memories and few level translators) are the actual loads attached with these switches. 

2. Can you share any oscilloscope shots?

Response : 

U202 - Working Condition

 

U202 - Non Working Condition

 

3. When does the device fail? During startup? During normal operating conditions? 

Response : 

The device is not failing during startup.

SoC and its associated peripherals (memories and few level translators) are the actual loads attached with these switches. Failure occurs when the SoC is powered down and powered up during normal runtime.

Also the test is being executed only in the normal room temperature.

4. Does replacing the device fix the issue such that the circuit operates normally?

Response : 

We are requesting the components for procurement. Once it is reached we will initiate the replacement of load switch.

One important concern on this replacement is that, Does TI has any special assembly instructions to remove and assemble the load switches on the PCB (especially during replace)?

5. Is this a prototype or production platform? 

Response : 

It is a prototype platform.

6. What is your thermal pad connected to, GND?

Response : 

Yes. Thermal pad is connected with GND only.

(Please refer the below mentioned layout snap for reference. The line marked in white color is the place where the load is disconnected to verify the functionality of switch without load).

Hi Devendhiran, 

Please refer to this document for SON PCB soldering techniques: http://www.ti.com/lit/an/slua271b/slua271b.pdf

Thanks for the detailed response! To clarify, the 1V8 load switch (U203) works properly, but the 3V3 LS (U202) does not? Looking at the schematic and the additional information you provided, I don't see any differences between 1V8 and 3V3 except the input voltage. Is that correct? 

Please let me know if you're able to replace the damaged TPS22965. I don't see anything incorrect with U203 from an applications standpoint, so I'm thinking the part might have been damaged during soldering or a potential short.

Thanks,

Arthur Huang

Hi Arthur Huang,

Thanks for sharing the PCB soldering techniques document.

For your note, 1V8 load switch also not working and exhibits the same behavior. As you said, except Input and output voltage there is no change in the connections of both load switches.

If you could able to provide us the list of situations or issues on which load switch fails, it will be helpful for us to trace the root cause.

You have mentioned that it might be damaged during soldering or potential short. So, Do you have any test measures (for e.g, impedance between each pins,etc) to ensure the mode of failure?

Finally, Does TI have any facility centers within India for assisting the component removal, validation and re-assembly? If so, it will be very much helpful for us.