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I NEED HELP TO SELECT A DEVICE

mehmetserdarcelik
Prodigy 250 points

Other Parts Discussed in Thread: INA300, INA301

Hey. I drive a dc motor. It's nominal voltage 6v and no load nominal current is 22mA. I want to know the current of the motor therefore i might know the torque of the motor. For example if the current is above the 100mA i'll stop the motor. For that, i need a current sensing device. One directional current..I connect the sensor to the microcontroller. So i don't need ADC i think..don't i? Thanks in advance.

  • 0
    Prodigy 250 points
    INA300 looks good. It has comperator module. So i can only send a inturrupt to the microcontroller. But first question is..this circuit is enough formmy current ranges? (for example can i arrange it to send an interrupt above 100mA?) And other question is that..This circuit is so little..I need easy soldering package..Is there bigger package of this integrated circuit? Thanks.
  • 0 in reply to mehmetserdarcelik
    TI__Expert 4595 points
    Hi,
    INA300 should be able to support the current range you need with 6 V common mode. What is your accuracy target?
    You can set the threshold either using a DAC or a limit resistor at the Limit pin. The threshold or the limit resistor value will depends on the shunt resistor value you choose for the given current range. For example let's say the maximum current you want to detect is 500 mA and given the full scale input of INA300 is 250 mV, you could choose a shunt resistor value = 250 mV/ 500mA = 0.5 ohm. If you want the current threshold to be at 100 mA then you can set the limit pin to 100mA * 0.5 ohm = 50 mV using a DAC or by using a 50 mV/20 uA = 2.5 K ohm limit resistor (note that you will need to add a correction factor (NAF) to this calculation if using the 10 usec delay setting).
    Regarding the package: Currently it is only available in the QFN package but it in the near future it will also be offered in VSSOP-10 pin package. You can also look into INA301 which is a current sense amplifier integrated with the comparator. This is available in VSSOP-8 pin package. Please let me know if you have any questions.
  • 0 in reply to Rabab Itarsiwala
    Prodigy 250 points
    OMG I'm greatful to you. Great explanation . But i think i do not have enough information about that issue. " What is your accuracy target?" Really i don't know exactly..My dc motor's rated current is 0.4 Amper. If i want to detect 0.5 A ..(And its okey +10 mA and -10mA error for detection) What should i use for shunt resistor?
  • 0 in reply to mehmetserdarcelik
    TI__Expert 4595 points

    If you want to detect 0.5 A then you can choose a shunt resistor < 0.5 ohm. +-10mA accuracy at full scale is achievable using INA300.