0
\$\begingroup\$

My current system:-

I'm working on a electricity metering system ,

I'm using shunt resistor configured in high side mode (a current sensor ) ,

I'm also using ADE7755 measuring chip ,

A schematic of the current circuit :-

enter image description here

A higher resolution schematic here

The problem:- When connecting the circuit as shown in the above schematic , R1, R2 , R3 & R4 blow up with some fire .

This isn't the first time happens , it happened before 3 times .

My initial guess it's that Analog & Digital ground are connected some how ..

I'm ready for any questions to clear the problem , thanks .

UPDATE#1 :-

I connected the PIN AGND in ADE 7755 chip to the Digital ground

\$\endgroup\$
3
  • 1
    \$\begingroup\$ What's the idea of posting an 11 Mpixel BMP image for a schematic? If you would use the PNG format it would be less than 100 kB, so you wouldn't need the ZIP. And you can easily scale it down by 75 %, without any concessions to readability. I edited the link. \$\endgroup\$
    – stevenvh
    Aug 25, 2012 at 18:19
  • \$\begingroup\$ @stevenvh for ppl who need zoom (like me :D ) thanks =) \$\endgroup\$
    – xsari3x
    Aug 25, 2012 at 18:24
  • \$\begingroup\$ I think you can do other things for better readability than going to huge image sizes. For instance there's a line running through the values of R3 and R4. Wait until Olin sees this :-). \$\endgroup\$
    – stevenvh
    Aug 25, 2012 at 18:30

1 Answer 1

Reset to default
3
\$\begingroup\$

If you look closely at the datasheet, you'll see that it plainly says the maximum signal you can apply to the amplifier inputs with respect to analog ground is +/- 1V (+/- 6V over voltage tolerance).

Your high-side current transducer is going to put a lot more common-mode stress than that on those pins, hence the blow-ups.

Consider a low-side sensor or an isolated transducer like a current transformer that can be referenced to the IC return.

Be safe - playing with the mains can be lethal. (I'm glad to see a fuse in your circuit!)

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.