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I am working on a project where I've taken an LDC1612evm (inductance to digital converter) and removed the connected micro controller portion to communicate with a TM4C123G LaunchPad via I2C. I have been able to get the circuit working correctly when connecting the launchpad to my computer through micro usb, the circuit looking like the picture below (the pull-up resistors are for the I2C communication) enter image description here

I connected an ammeter to the LDC input to determine the current draw of the chip, which being 5mA was within the operating limits found in the datasheet. For the end product, this circuit is going to have a 12V source passed through a MC7805CT 5V regulator to control this particular section. I have attempted to simulate this as is shown in the below diagram enter image description here

Here is where the problem occurs. When I read the ammeter I see a current of 500mA flowing into the LDC which, not surprisingly, instantly damages it.

So my question is what is causing the huge current draw?

I have checked the LDC input voltages and in both cases I get the expected 3.3V. It has been suggested that the micro controller section of the ldc1612evm has a regulator on it thus by removing that portion the regulator is bypassed allowing for the higher current draw, but from what I can tell from the launchpad's datasheet power schematic the 3.3V output contains a similar regulator, so I don't understand why that would be the problem.

Thank you in advance for any insights into the cause.

EDIT: changed out the wiring diagrams for schematics

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  • \$\begingroup\$ Welcome to EE.SE! Please take the Tour at electronics.stackexchange.com/tour. Please draw a schematic! \$\endgroup\$
    – winny
    Commented Mar 19, 2019 at 20:03
  • \$\begingroup\$ I agree, a picture is no substitute for a schematic, they are hard to read \$\endgroup\$
    – Voltage Spike ♦
    Commented Mar 19, 2019 at 20:06
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    \$\begingroup\$ It looks like you are using Fritzing. Fritzing can produce schematic diagrams as well as the wiring diagram you have posted. Wiring diagrams are of little use when discussing the function of a circuit. Please coax a proper schematic diagram out of Fritzing and post that. \$\endgroup\$
    – JRE
    Commented Mar 19, 2019 at 20:06
  • \$\begingroup\$ I apologize for not using the correct formatting. I will get a schematic up as soon as possible. I had to create a design for the LDC so it might take me a few minutes. \$\endgroup\$
    – Phillip S.
    Commented Mar 19, 2019 at 20:13
  • \$\begingroup\$ @JRE Coax? That’s... odd. \$\endgroup\$
    – winny
    Commented Mar 19, 2019 at 20:15

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Looks like LCD1612 3.3 volts is an output from a linear regulator derived from the USB and Launchpad 3.3 volts is also an output from a linear regulator. You have two voltage outputs tied together. You don't need to connect these.

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  • \$\begingroup\$ I removed the controller portion from the LDC1612evm and with it the regulator that originally fed 3.3V to the LDC chip. So I should only be receiving input voltage from the launchpad's 3.3V. I believe that is what you are referring too, but if you meant something else, please let me know. \$\endgroup\$
    – Phillip S.
    Commented Mar 19, 2019 at 21:43

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