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Measuring 2.5uA threshold current

Kwan
Intellectual 510 points

Other Parts Discussed in Thread: TIPD104, TIPD129, LM7705, INA326

Hi,

I would like to detect threhold current of 2.5uA, so i require a current shunt that has low input current. Is there any current shunt with voltage out put i can use? Also, due to mechanical constrain, my package cannot be more than 1mm height.

  • 0
    TI__Expert 4595 points
    Hello Kwan,
    Please take a look at TIPD104 - Current Sensing Solution, 10uA-10mA, Low-side, Single Supply. We will get back to you on Monday.
  • 0 in reply to Rabab Itarsiwala
    Intellectual 510 points

    Hi, I prefer high side sensing in my design. LT6118 seem like meet the requirement, due to low input offset current. Pls advise is there solution in TI to meet 2.5uA threshold current in Avalanche photo diode.

  • 0 in reply to Kwan
    TI__Expert 4595 points

    Hi Kwan,

    Please share with us the system details like supply, bus voltage and a schematic if possible. Also are you trying to implement something like this TI design http://www.ti.com/lit/ug/tidu535/tidu535.pdf. I am moving this post to Precision Amplifier forum and someone will assist you soon.

  • 0 in reply to Rabab Itarsiwala
    Intellectual 510 points

    Hi Rabab,

    It’s high side sensing.

    The common mode voltage is 3.3V typ.

    The design is quite simple. There is a current source which provides 0mA(min) to 2mA. This is connected to ADC in our controller IC. Beside this, I want to sense 5uA and 10uA to alert the low current.

    When it is 5uA, the alert should be on. When it increased to 10uA, the alert should be off. In order to avoid the fluctuation of the alert, I need about 5uA hysteresis.

  • 0 in reply to Kwan
    TI__Mastermind 25875 points
    Hello Kwan,

    I recommend modifying TIPD104 for your load current range. It should also work on the high side since the input common-mode range extends 100mV beyond the positive supply voltage. Please note that the output voltage swing, like all other amplifiers, is a subset of the supply voltage. For example, given supply voltages of ground and 3.3V, the output swing of the INA326 is from 75mV to 3.225V. Also note that in order to sense no current flow (0A), you will need to calibrate each system. Therefore you might find TIPD129 interesting. That reference design also uses the LM7705 to generate a small negative supply voltage so the output can reach 0V.