All,

I figured out the problem.  I didn't have a ground between the load circuit
and the logic supply.
In other words, the chip power supply (5V0 and the measured circuit share a
common ground.  I didn't
Have the common ground connection.  After I connected each ground together,
it works like a champ.

Thanks to all for the suggestions.  I appreciate it.

Regards,

Jim=20

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Mike Hord
Sent: Wednesday, July 02, 2014 3:51 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE]: Texas Instruments INA219 Current Monitor IC

I've used some of the other INA family chips; they generally just work.

The INA circuitry shouldn't affect the voltage drop across the sense
resistor much; the inputs on the INA are quite high impedance.

I think something deeper is wrong here- a layout or assembly issue,
perhaps.

Mike H


On Wed, Jul 2, 2014 at 2:30 PM, <jim@jpes.com> wrote:

>
>  All,
>
>  Does anyone have any experience using the T.I INA219 (or T.I. INA220)
> part?  It is a current monitor chip that
>  measures voltage across a series current sense resistor, measures the
> voltage from the bottom of the sense
>  resistor to ground, and then calculates circuit current and power.
>
>  The problem I am having is no matter what I do to setup the chip, the
> bus voltage (voltage from bottom of sense
>  resistor to ground) always comes out to around .9V.  However, the input
> voltage is ~3.0 volts.  The voltage
>  across the sense resistor measures a few mV, which is what it is
> supposed to measure.  The bus voltage is then
>  the  voltage at the input (3.0V) minus the voltage across the shunt
> resistor.  This should be around 2.95 volts.
>  But again, I only read about .9 volts or so.
>
>  If anyone has any insight into this, I would appreciate hearing your
> inputs.  I have contacted the T.I. help
>  desk, but was told it would be between 1 and 2 weeks for an answer.  I
> would prefer an answer quicker than that
>  if at all possible.
>
>  Thanks and Regards,
>
>  Jim
>
>
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