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INA219: I2C interface issue

Jens Johansson76
Prodigy 30 points
Part Number: INA219

Hi,

We are using an INA219 in a prototype circuit and have ran into an issue. Basically, whenever the INA219 circuit (which is on an isolated board) is connected to the main controller circuit, containing the MCU the entire I2C bus goes defunctional and the MCU halts. To isolate the issue we hooked to INA219 circuit directly to a small test board containing only a MCU, voltage regulator, crystal etc, basically a dev board and the same thing happens. When looking at the I2C channels with a scope the SCL is continuously running a square wave and the SDA is low, which seems odd since there are pull ups on both channels of 3K3 Ohms. As long as the INA219 is unconnected the bus looks fine and all commands from the MCU appears.

The INA219 circuit itself is nothing special, 5V in with a 100nF Cap to Ground with Ground going to pins 1, 2(to set address) and 6, 5V to pin 5, SCA to 3 and SCL to 4. The bus voltage goes through 2 parallell resistors to get the required Rs for our applications and into pin 7 and 8.

The entire system is 5V so there should be no issues with the I2C busses not being pulled high enough etc. We've also tried different software implementations which doesn't seem to make a difference. We have also tried replacing the INA219 itself, also to no avail.

Any ides will be gratefully accepted!

  • 0
    TI__Genius 14825 points

    Jens,

    Thanks for your question, could you confirm you have the right pinout for the package - there are two:

    Next, can you confirm that you're not somehow tying SDA to A0 or A1 and also to GND with external passives.  Sometimes I put options to tie A0 and A1 to multiple sources to change the address, and if I were to hook A0 or A1 to both SDA and GND, that would create the behavior you're seeing.  However, if you remove the INA219 and the bus returns to operation, then it's probably not A0 or A1 hooked to an external passive.

    Have you tried using the INA219EVM, and perhaps wiring up the daughterboard using the T1-T4 headers directly wired to your control board to verify operation?

    Those are the first thoughts I have - let us know if one of these leads you to the answer or if you need further debugging assistance.