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I designed & assembled 3 copies of a circuit (BNO055 motion sensor board, used recommended i2c application from the datasheet).

1st one had some soldering issues, fixed them and it worked, received sensor data. 2nd one worked with no issues. 3rd is the culprit.

When I power the board everything looks fine, the ON led lights up, no smoke, no noise of any kind. The power supply shows 2mA current. But no data comes from the sensor.

Somewhere around 15th second the current starts to increase slowly. Around 20th second current reaches 10mA, after that within seconds the current reaches to 50mA and I cut the power, to protect the circuit.

I checked all the solder points, connector pins, etc. No bad solder, no short.

I connected the power again, same thing happened.

I wonder what would cause this behavior and how can I troubleshoot this problem.

I attached the schema & picture of the board

Schema of the circuit

circuit board

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  • \$\begingroup\$ Is that the full schematic? I think I see more than two chips on that board but it only shows one in the diagram. Where is your sensor input? Is it pins 19 and 20? The labels are hard to read. \$\endgroup\$ – MichaelK Mar 29 '16 at 1:13
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    \$\begingroup\$ Eagle has a "Resolution" field when you export an image (assuming that's how you captured the schematic image). Increase the dpi value and repost the image. It's hard to read the fine print. \$\endgroup\$ – Dan Laks Mar 29 '16 at 1:15
  • \$\begingroup\$ How much current do the other copies draw? Do you have an oscilloscope to check if there is signal in pin 27? \$\endgroup\$ – berto Mar 29 '16 at 1:16
  • \$\begingroup\$ I added a better resolution image. the other boards draw 2-3 mA current. \$\endgroup\$ – dvdmn Mar 29 '16 at 1:21
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    \$\begingroup\$ Check the polarity of any polarized caps (only C7?). That behavior sounds like a tantalum cap right before it exploded :) \$\endgroup\$ – bitsmack Mar 29 '16 at 3:12

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