TPS7A8300: TPS7A8300RGWR: Vref Varying from chip to chip

Hello,

          Since the ANY-OUT feature is being used, could you confirm if the SNS pin is connected to the Vout trace in your circuit? It would help us if we could have a look at your schematic that shows the connections made to the LDO. Thanks!

Regards,

Srikanth

Hello,

         Apart from above, please also verify if an Input capacitor larger than or equal to 10uF is in place. Thanks!

Regards,

Srikanth

Yes, SNS is connected to the Vout trace.

Input Capacitor is 12µF. Please ref uploaded schematic

Hello,

         The attached schematic has some pins muddled up, hence some connections are not very clear. Could you clarify the following:

(a) Since the ANY-OUT feature of the device is being used, could you confirm if the feedback resistors (R3_Adj & R4_Adj) are unpopulated when the measurement is made?

(b) Could you confirm that the EN pin is not floating and is connected to an appropriate DC  source?

(c) The schematic shows that the target output voltage is 3.3V, but all the programmable pins are connected to ground via 0Ω resistors R18-R28. Am I correct in assuming that for 3.3V output only resistors R20, R26 and R28 are populated and for the measurements made above none of the resistors were populated?

Thanks!

Regards,

Srikanth  

(a) The feedback resistors (R3_Adj & R4_Adj) are unpopulated.

(b) The EN pin is connected to +5V

(c) We were to connected 0Ω resistors at R20, R26 and R28 to ground to get the target volatge of 3.3V at the output.

But we found voltage at Vout (when all the programmable pins are open) is greater than 0.8V and also different from IC to IC.

Thats why the programmable resistor combinations (R18-R28)  varies from board to board.

Hello,

         Its rather unusual that the voltage on the FB pin and the voltage on the NR pin are not equal to each other. At this point I suspect some leakage to be present amongst the Any out programmable pins. Could you try cleaning the boards and verify if the issue remains? Could you also swap the units among the boards to see if the fault follows the units? Thanks!

Regards,

Srikanth 

Yes, we have already done these. 
As I mentioned it earlier, we didn’t face the problem with any of the five samples (TPS7A8300RGR) that we got from you. 
Could it be the problem with this lot? 

So far we tried six ICs by assembling them on two different pcb designs. For all the six ICs,  Vref as well as Any-out programmable output voltage was not as per the specification.

Please note we have procured sixty numbers of these ICs from Mouser (Purchase order no. TIFR/1180317/12P0213) in Feb 2019.

Will I get replacement for the entire lot?  If so, do we have to desolder and send the used ICs?

Thank you.

When we are about to procure a new lot as our deadline for the project is approaching.

But to our surprise we saw the lead time mentioned by the distributor is 35 to 70 weeks!

This may cause a big setback for us.

Even if we revert back to our older choice of TPS7A8300RGR, the lead time of supply is around 80 week.

Please clarify why so much lead time. We need min. 50 no.s by December end of 2021.

Thank you

Hello,

         I am looking into this, I will get back to you by the end of the day tomorrow. 

Regards,

Srikanth 

Hello,

         Since the units were purchased from Mouser, whether or not soldered units are returnable would depend Mouser's return policy. Please contact them to begin to the product return process. Regarding the long lead time, across the Semiconductor industry there is a global supply chain shortage and unfortunately we are not immune to that.

         Could you clarify if you are using the RGR package or the RGW package? If you are using the RGR package, it might be possible for us to ship some samples across. Thanks!

Regards,

Srikanth