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INA226 - Question concerning my schematic

Philipp Gypser
Prodigy 10 points
Other Parts Discussed in Thread: OPA333, TIDA-00528, INA226, LM3940

Hi,

I currently try to build my own power measurement with the help of the application note TIDA-00528 (40 V to 400 V Uni-directional Current/Voltage/Power Monitoring Reference Design). I changed some parts from the schematic because I only need to measure 100V and 5A at maximum. The schematic and the layout is attached. I use the INA226 and the OPA333. The Shunt Resistor is a WSL3637 from Vishay.

The main problem that I’m facing is that I can measure a voltage drop across the Shunt Resistor (10mOhm, 1,5A) of 15mV but I can’t measure this voltage drop across the other 10Ohm Resistors (R2, R6). I can’t see any mistake if I compare my layout to the one from the Reference design.

My load is currently a heating cartridge and I use the Statron 3221 as a power supply. The INA is powered by an Arduino UNO R3 or rather the LM3940. I also tried to read data from the INA and that seems to be fine, however the readings are all zero because there is no voltage drop developed across the resistors.

Did I connect the VBUS Pin in the right way for a High Side measurement?

Is the IRFR6215PBF a suitable substitution for the IXTT16P60P that was used in the application note?

I have a voltage divider at the VBUS Pin with a ratio of 40 (300kOhm / 7,5kOhm). Is there a problem with the ratio because in the application note there was binary ratio of 64 in use?

Thank you in advance.

  • 0
    TI__Genius 15760 points
    HI Philipp,

    I will need some time to go through all the details. The designer of this TI design is no longer working with us so I need to understand the design anto be able to provide useful pointers.

    Regards
  • 0 in reply to Mayrim Verdejo
    TI__Genius 15760 points
    Hi Philipp,

    I have been looking at this for a few days and there is nothing that I could detect either. I would recommend you connect the Vbus divider the same way Rabab did on her design, with the binary ratio of 64 (Page 7) and try that out. The MOSFET seems very similar to the one from the design.

    If you have one of our EVMs I would recommend you evaluate the device outside the application and make sure is working perfectly.