LIS2DH taking more than 100 uA

[PK.1]

We are using LIS2DH in our board for production. Among 1000 boards, about 50 boards were drawing much more power because of LIS2DH (the IC is functional - we are getting the accelerometer data). Once we remove the IC from the board, current dropped from >100 uA to a few uA.

What can be the reason?

[Eleon BORLINI]

Hi @PK.1​ , supposing the schematic is ok, do you perform x-ray to check if there are any short circuits below the soldered pads? Which is your Vdd voltage operation? Regards

[PK.1]

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[PK.1]

Hi @Eleon BORLINI (ST Employee)​ ,

Thanks for your reply. All boards have been 100% X-Rayed after production and no anomalies were found.

However, after some testing, I found the issue:

We had put a 0 ohm resistor (RC1005J000CS) before the accelerometer module for debugging purposes. When I remove the 0 ohm resister and bridge the footprint with solder, the current draw had become normal. So it seems that the 0 ohm resistor is causing the issue. We tested this on 7 boards till now and got them all working.

Any ideas how it would affect the accelerometer?

The Vdd voltage is 2.7 - 3.3V

Thanks!

[Eleon BORLINI]

Hi @PK.1​ , thank you for the analysis. So there is an effective HW difference among the boards. On which line did you put the 0 Ohm resistor? Regards

[PK.1]

Hi @Eleon BORLINI​, I have put the resistor between battery voltage and Accelerometer VDD. PFA the schematic. R204 is my 0 ohm resistor.

[Eleon BORLINI]

Are there other connections on VDD_ACC net? To summarize the issue, all the 1000 board have this R0 component but you found an over-current consumption problem only on 50 of 1000 board. On these 50 boards, when you remove the R0 and substitute it with a direct short (solder bridge), the issue is no more there. For this reason, the problem should be in that part of the circuit... You have to be sure that the resistor is not overlapping on other parts of the PCB (such as vias, exposed lines etc).. What I can suggest you is to un-solder these R0 resistors, check if they are effective 0 Ohm and then solder them again on the issued pcb. Regards

[PK.1]

Hi Eleon,

Apologies on the late reply.

There are no other connections to the VDD_ACC net.

The R0 resistors are effective 0 ohm. Also, in a few boards I bridged the resistor with solder, then current dropped to normal.

We are checking our PCB Design and possible fabrication/SMT issues that might have caused this problem.

Thanks for your help!

Best,

Prathyusha