LP87702-Q1: no output from SW_B0 after board ran some time

Chris Meng

Part Number: LP87702-Q1
Other Parts Discussed in Thread: LP87702, IWR6843ISK

Hi,

My customer connected IWR6843ISK to their own system. But after some time, some ISK boards can't work ok. And we found the SW_B0 of LP87702 outputs 0V which is not expected. But SW_B1 of LP87702 works normally (output 1.2V). The resistance value of the inductor L4 (connects to SW_B0) on issue board is similar as the one on working board.

Customer connects the 3.3V power supply/ some GPIO/ UART/NREST signals from ISK connector to their system. No 1.8v from PMIC LP87702.

What may cause such problem? Any comment is appreciated!

Pls find ISK related sch below. You can find full ISK sch in PROC073A(001)_Sch.PDF at http://www.ti.com/lit/zip/swrr164

over 5 years ago

0 Chris Sterzik over 5 years ago

TI__Guru 63481 points

Chris,

Can you provide some more details about the number of units failing and how long it takes for the units to fail? I will direct your question to the product expert.

Regards,

Chris

0 Chris Meng over 5 years ago in reply to Chris Sterzik

TI__Mastermind 37706 points

Chris,

Customer feedback 4 pcs of issue boards.

I am waiting for customer's feedback on how long it takes these boards to fail.

0 Chris Meng over 5 years ago in reply to Chris Meng

TI__Mastermind 37706 points

Chris,

Customer feedback that the total time to use these 4 pcs boards are about 2 days.

0 Tuomo Alatalo over 5 years ago in reply to Chris Meng

TI__Intellectual 950 points

Hi Chris,

There is no known issues with LP87702D-Q1 device where B0 will shutdown after some time period.

After B0 shut down, is it possible to start up again via I2C? Will it give interrupt?

Is it possible to get oscilloscope plots from VIN, B0_VOUT and I2C during unexpected shutdown?

Also I would recommend to check device soldering.

Best regards

Tuomo

0 Chris Meng over 5 years ago in reply to Tuomo Alatalo

TI__Mastermind 37706 points

Tuomo,

Thanks for your reply.

Sorry, it seems that I didn't describe the issue clearly. Let me explain again. The issue boards were used to be working ok and LP87702 outputted voltage correctly. But now, the SW_B0 of LP87702 outputs 0V after power on the boards, but SW_B1 of LP87702 outputs correct voltage on each issue board.

Would you pls help again?

0 Tuomo Alatalo over 5 years ago in reply to Chris Meng

TI__Intellectual 950 points

Hi Chris,

So the B0 problem is permanent, correct?

Is the customer made measurements on board? Following cases are possible, since the board has been working previous: B0 VOUT has been shorted and device is broken or some other BUCK0 input/output component might be broken, for example capacitor since they seems to be close to board edge.

Are they able to read I2C from the device? What interrupts device generate?

Tuomo

Power management

Power management forum

LP87702-Q1: no output from SW_B0 after board ran some time