LIS3DH ADC function problem

Jason Kuo · ‎2018-01-12

Posted on January 12, 2018 at 13:07

Hi, I got a problem in LIS3DH ADC function, we use LIS3DH ADC1 to detect the battery power in our product, but now we found that ADC can't work in the new lot of LIS3DH, the date cod is 8734. And the lot of data code 8518 is the last lot we used and it works fine in our product. Can anyone help me to find if any change in LIS3DH ADC function after the data cod 8518?

And please refer my attached pictures to show the I2C waveform, the data always is 0 when we read out from ADC1 register of date code 8734 chip. The waveform of date code 8518 chip can show the right data of ADC1.

#lis3dh-adc-function-problem

Miroslav BATEK · ‎2018-01-15

Posted on January 15, 2018 at 14:54

Hi, I'm looking for more information, I will come back to you as soon as possible.

I suppose the software/firmware is exactly the same for both sensors?

Miroslav BATEK · ‎2018-01-15

Posted on January 15, 2018 at 15:19

Can you please check that the BDU bit (bit 7) is set to 1 in CTRL_REG4(23h) and the ADC_EN bit (bit 7) is set to 1 in TEMP_CFG_REG (1Fh)?

Jason Kuo · ‎2018-01-15

Posted on January 15, 2018 at 16:19

Yes, we didn't change the HW circuit and FW, change the chip to old lot (DC:5818) then it works fine. Both BDU and ADC_EN are set to 1.

Miroslav BATEK · ‎2018-01-15

Posted on January 15, 2018 at 16:47

Could you please do the register dump from 0x00 to 0x3F of the good and bad part.

Jason Kuo · ‎2018-01-16

Posted on January 17, 2018 at 07:36

Hi, we found the problem in our device, there is a error in our FW design, the BDU bit will be set to 1 during initial process, but after that, an abnormal action clear it. When we fix ths abnormal action then ADC work fine in the new date code chip.

But I am curious about why the old date code (8518) chip work fine when BDU bit was cleared, but new date code (8734) chip can't. What the different between them?

Anyway, thanks for your help.

Miroslav BATEK · ‎2018-01-17

Posted on January 17, 2018 at 11:44

I don't have any detail information but it seems the ADC was modified. Anyway the requirement for the BDU bit is written in the d

http://www.st.com/content/ccc/resource/technical/document/datasheet/3c/ae/50/85/d6/b1/46/fe/CD00274221.pdf/files/CD00274221.pdf/jcr:content/translations/en.CD00274221.pdf

in chapter 3.7.