LP38690: Inquire about the cause of the defect

Hello,

         Just to make sure that I understand you correctly, you experienced low output voltage with one LP3869 device and when you swapped it with a new LP3869 device, the issue went away? Do you have an input and output cap of at least 1uF in place? It would help us if you could share a schematic showing the connections to the LDO. Thanks!

Regards,

Srikanth

Hello

I'm the customer for this issue.

when I replace it with a new LP38690, the problem was resolved.

The inputs has a caps of 1uF, 100nF, 1nF.

The output has a caps of 33uF, 1uF.

This is the circuit diagram for the LDO connection

Thank you.

DSHa

Hello,

          The schematic looks good. Would it be possible for you to provide us some scope shots showing Vin, Vout and Iout during startup and steady state on the faulty unit? This is to ensure that abs max ratings are not being violated and to verify if the part is stable upon being loaded. Thanks!

Regards,

Srikanth

Hello

Defective units have already been repaired.
Therefore, we cannot provide scope shots.

A problem occurred while the device was operating normally.
Customers who have used our products must be informed of the cause of the problem.
But since I've never experienced this, I inquired about the possibility of having this type of problem.

Please advise on any issues that may be causing the above error symptoms on the LP38690.

Thank you

Hello, 

          I am looking into this, I will get back to you on Monday of next week (11/29) after Thanksgiving.  

Regards,

Srikanth

Hello,

          Could you confirm if the input current when the part is loaded was around 230mA? I am wondering if some contamination during addition of load might have caused the load current to exceed the current limit of the part or exceed the current limit of the 5V input supply which would cause the Input supply to droop and output voltage to also fall. Thanks.

Regards,

Srikanth

Hello

The load current of the 3.3V output power supply is 0.230mA.
The 5V current of the problematic device was measured lower than that of the normal product.

The part we tested is the LP38690 and we know that the device has an output current of 1A.
I also used a power supply with the 5V input supply's current limit set to 10A.

Please advise on any issues that may be causing the above error symptoms on the LP38690.

Regards

Hello,

         Could you provide me scope shots showing Vin, Vout and Iout during startup and steady state on a working unit? This is so we may rule out any violations of Abs Max ratings. Thanks!

Regards,

Srikanth

Hello

All products have been repaired and measurement is not possible.
Could this issue be caused by one of the conditions below?

1) When Vin is higher than the abs max value
2) When the voltage of Vout is higher than abs max at start
3) When Vin is shorted to GND

Regards.