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AMC1106E05: AMC1106 High Current Reading at Startup

Part Number: AMC1106E05
Other Parts Discussed in Thread: TIDA-01094, AMC1106M05, MSP430F6779A


In the electricity meter design we use AMC1106 as external sigma delta modulator for current measurement, we are getting too high readings from ADC's connected to DOUTs of the AMC1106 at device startup (power on), and after nearly 3-5 seconds values settle down and we are getting relavent readings from ADCs. What can be the cause of this, have you ever had a similar issue before? 

The reference hw/sw design we use is:

Here is the phase current sensing part of our design, could you please check whether there is anything wrong with the schematic or could it possibly be about software part?

I can also share the full schematics of our design on e-mail if you'd like to check it. 

Thanks for your help in advance.

  • Hi Utku,

    Can I ask you how much of the TIDA-01094 reference design you are using?  The AMC1106M05 itself should not be causing the problem, but you can try to verify that by removing the diodes and make sure that AGND is tied back to your shunt. 

    I was talking with the author of the TIPD-01094 document and he mentioned that there are digital filters in the software that need to settle before you get the expected data.  Let us know and we'll try to get you settling faster.

  • Hi Tom,

    Thanks for your quick reply.

    Our design has not much differences from TIDA-01094, let me share the MCU block too. How long it takes digital filters to settle? Do we need to do extra steps in the software to wait and get the expected data after settling? How can we avoid to use that faulty data at startup in the energy calculating?

    In that schematic we use MSP430F6747AIPZ but we had to assembly MSP430F6779A intead because the samples we've got is that P/N. Maybe it can cause any problems?

  • Hi Utku,

    I'll need to dig into the software a bit more and may ultimately have to refer you to the MSP430 team for additional help with this query.  Have you tried removing the diodes and shorting AGND to AINN?  If so, did that make a difference?

  • Hi Utku,

    Have you made any progress here?  Does removing the diodes have any impact on your settling time?