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INA226: INA226 open load

Florian Boese
Prodigy 10 points

Part Number: INA226

Tool/software:

Hello,

I use in my circuit 5 x INA226. It is for a power ditribution devide. On each channel I have a shunt with an INA226. If I connect a supply or a load to the channel it is working fine (Giving correct current and shunt voltage values back). But if I let the channel open (with out load or supply) its gives me sometimes 0xFFFF back. I can't under stand the behavior, because the open chanel is still connected internaly, so it sill sees 12V at VBUS and +Vin and -Vin. I expect that it always deliver about 0V for shunt voltage and 0A for current.

What did I do wrong?

  • 0
    TI__Genius 10300 points

    Hi Florian,

    Are you reading 0xFFFF in the shunt voltage or current register? Does it stay at that value? Please help clarify what you mean by sometimes reads 0xFFFF.

    Thank you,
    Mallika Senthil

  • 0 in reply to Mallika Senthil
    Prodigy 10 points

    Hi Mallika,

    thanks for your respons.

    I read sometimes 0xFFFF not always. It depends where I connect the supply. In the example above it happens on Ch2. But never on Ch1. If I connect the 12V source to Ch2, Ch2 would be fine and some of the other channels show this behavior. 

    0xFFFF is read from the shunt voltage and current register. (If it only would be on the current register, I would expect that something with calibration is wrong.)

    If I connect to any of the open channels an additional supply OR a load than it shows good values. 

    (By the way: In the picture it must be Rshunt_1 and Rshunt_2 and so on. For each INA an own shunt resistor.)

  • 0 in reply to Florian Boese
    TI__Genius 10300 points

    Hi Florian,

    If you convert 0xFFFF to an actual voltage, you'll see it actually represents a negative voltage in 2's complement.

    0xFFFF =  - 2.5uV

    You're probably reading a small negative voltage due to either noise or due to lack of grounding since both Vbus supply and load are disconnected, i.e., system ground is floating.

    Best,
    Mallika Senthil