LP876242-Q1: No power output from LP876242B0RQKRQ1 using TIDA-020047 design

Hi Yin,

So, is it the same customer whom you are referring to another E2E thread ? 

Can you share schematic of customer board? 

Best regards,

Ishtiaque Panhwar 

Ishtiaque,

It is another KMM customer, they fully used TI design files in TIDA-020047, not did any changes, just sent out the CAD file for manufacture.

U can download the design files from below link.

https://www.ti.com/tool/TIDA-020047?keyMatch=TIDA-020047#design-products

Andy

Hi Andy,

Thanks for the customer information. 

Yes, I got it that they are using TI design but how can I tell what is problem without sharing any information. 

I need to look at customer schematic to see if there are any discrepancies and if the schematic is okay then we need to know how they are trying to power up the device. There could be layout issue as well. So, I need to have some information.  

Best regards,

Ishtiaque Panhwar

Ishtiaque,

Mentioned before, they just downloaded the TI design files, fully reused the schematic, layout, not do any changes. Sent out the downloaded CAD files output for manufacture. 

Hello Andy,

Okay understood. But still they have to check if there is manufacturing issue in layout.  

So,  you are saying the device is not waking up. 

What checks they have done so far? 

1. Is the 3.3V input voltage available to the device from LM53625 ?

2. Is the 5V available from TPS61379-Q1? 

And provide some information to start with. 

Best regards,

Ishtiaque Panhwar

Hi Ishtiaque,

Customer connected the VMON1(GPIO7) with an external 1.2v power, then there is output and the LP876242 work fine.

My question is on TIDA-020047 the GPIO7 is connected with 1.2v output from itself, if PMIC depends on 1.2v, why here triggered by itself, cannot understand and it confuse me a lot, can TI EVM work well as the design without any changes?

Look forward to your comments. Thanks.

Andy

Hi Andy,

Yes 1.2 V is monitored by GPIO7 there is some delay for monitoring. If the PMIC don't see voltage on the then it won't power up. I will get back to you exactly how exactly this is done. 

Thanks!

Best regards,

Ishtiaque Panhwr

Ishtiaque,

any update here on the 1.2v monitor sequence in PMIC, thanks.

Hello Andy, 

So, I have looked into the NVM. It seems that VMON1(GPIO7) should be provided 1.2V within 4ms period. Otherwise, then PMIC will shutdown. 

so, either BUCK2 is taking longer to ramp up or there is voltage drop on the LC filter and because of that VMON1 is not getting 1.2V exact voltage. In the design 1.2V is point of load.  Have you asked the customer to share the start up behavior captured on the scope? Please if you can ask the customer to share the behavior captured on scope that would help to analyze behavior more clearly. 

Best regards,

Ishtiaque Panwhar