• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 174 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ACF2101: Application Inquiry

Renan Santos Adriano
Mastermind 18225 points
Part Number: ACF2101

Hello Team,


Good day.

My customer is planning to use the ACF2101 and wanted to clarify few things. According to the datasheet the integrator output voltage range is -10V to 0.5V. All of the application examples show input current flowing into the integrator. Is there any issue with reversing the polarity?

They have a current sensing toroid and they were able to reverse the current direction and the integrated output voltage was just a mirror image. Designing their application so that the integrated output voltages are positive eliminates the need for inverting amps downstream when they are trying to sample with a microprocessor ADC. They just need to know if long term the chip could be damaged in this mode. For the test, they were using +/- 12V power rails on the chip. Plan on adding clamping diodes to keep the output voltage levels within the operating voltage range of the micro ADC.

Also is there any reason the chip can't be powered with +/-5V. Their integration times will always be less than 4us so with a slew rate of 1V/us the largest output they would generate +/-4V. Again the spec sheet says V- between -18V and -10V.

Regards,

Renan

  • 0
    TI__Guru* 93105 points

    Hello Renan,

    The ACF2101 input current is required to be in the one direction indicated by the datasheet. Additionally, there is a Burr-Brown Applications Bulletin that provides a definitive statement about the input current "The ACF2101 is a dual, switched integrator that is typically used to convert a positive input current to a negative output voltage by integration, using an integration capacitor (CINT) . . ."

    https://www.ti.com/lit/an/sboa029/sboa029.pdf

    Therefore, the input current direction shouldn't be reversed in the standard application. The Applications Bulletin provides in Figure 3 an input offset current circuit that allows a bipolar input current to be applied. 

    "They just need to know if long term the chip could be damaged in this mode. For the test, they were using +/- 12V power rails on the chip. Plan on adding clamping diodes to keep the output voltage levels within the operating voltage range of the micro ADC." It's not exactly clear how they are connecting the output. Is there a schematic?

    The ACF2101 is a legacy product and it does not incorporate any special internal circuitry to protect the output. Therefore, the burden for protecting its output from an unusual voltage condition would be solely upon the user.

    "Also is there any reason the chip can't be powered with +/-5V. Their integration times will always be less than 4us so with a slew rate of 1V/us the largest output they would generate +/-4V. Again the spec sheet says V- between -18V and -10V." The ACF2101 datasheet lists the supply ranges; Positive Supply as +4.5 to +18 and Negative Supply as –10 V to –18 V. I recall the device will not function with a negative supply as low as -5 V.

    Regards, Thomas

    Precision Amplifiers Applications Engineering