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INA236: DDF (SOT-23) Version IN+/- clamps at +0.7V

Kai Scheffer
Intellectual 400 points
Part Number: INA236

Hello,

I was using the DSBGA Version of the chip for high side (+12V) current measurement. Now I redesigned the board to use the DDF package.
With this new version I can successfully communicate (I2C) and measure currents only when on low side (GND) related shunt. As soon as I try to go with the common voltage > 0.7V the device starts to clamp and I cannot use it for high side measurements in the +12V region.

I verified the board and only the INA236 makes this trouble when mounted on the board. When injecting voltages > 0.7V on either IN+ or IN- the pin starts to draw current. I have verified this behaviour and all 3 devices for testing.

Have you veered high side > 0.7V operation for the DDF packaged devices?

Best regards
Kai

note:  D6 is NOT in the actual layout and therefore not mounted.

note: inner layer In2 (GND plane) not shown. Inner layer In1 top half GND and lower half +3.3V. 

  • +1
    Guru 140200 points

    Hi Kai Relaxed,

    what shunt do you use and what current is flowing through it?

    Kai

  • 0 in reply to kai klaas69
    Intellectual 400 points

    The shunt is external and uses 2 x 100 uOhm parallel with a current range of +/-400A DC.
    Since the design uses an aluminium housing with SMD shunts mounted on Alu PCB in a front panel configuration isolation (high side measurement) is important. 

    There must have been a short somewhere to the housing/GND and on top I used wrong polarity for testing the high side voltage -> so clamping is actually -0.7V which is OK. So high side up to 30V works now. Sorry for the heads up here - the two more years ('67) didn't help to double check better Nerd

     

  • 0 in reply to Kai Scheffer
    TI__Mastermind 19375 points

    Kai S,

    Looks like Kai K got you where you needed to get to before I even got to the party! Please let us know if you have any additional issues or questions!