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INA195: Current Limiter Circuit for 10mA

Part Number: INA195

I want to limit o/p current limit at 10mA for -3.5V supply regulator.

Can we use current sense INA195 and comparator TLV3201 to control the EN pin of -3.5V regulator to limit the current at 10mA ?

please ASAP

15 Replies

  • Is this a switching regulator? Can you provide us more details regarding the complete circuit?
    We have a couple of devices with built in comparator that might be a better choice (smaller footprint, built in hysteresis)
    The INA195 and the TLV3201 might work, what accuracy are you looking into?

    Kind Regards,

    Carlos S., TI Sensing Products, Applications Support

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.

  • In reply to Carlos Silva85:

    we are planing to use LM27761 regulator to generate -3.5V O/P. The only thing we want to control O/P current to 10mA.

    -3.5V Supply spec are :- 

    Vin = 5V

    Vout = -3.5V (Negative voltage) +/-5%

     Current limit power up = 10mA 

    Steady State current = 5mA

    Ripple   =  10mV RMS @ 1MHZ.

    Please suggest the suitable approach to meet this requirement.

  • In reply to RAHUL SHARMA52:

    For the required accuracy, the correct approach is to modify the feedback loop on your chosen regulator to throttle back the output should the maximum current be exceeded. 

    A standard current sense amplifier cannot be used for this purpose, since both loops (voltage and current) need to be combined using a diode, which would introduce errors due to the non linear current versus forward voltage characteristics and the associated voltage drop. The LMP8646 was designed with this in mind and has an internal diode compensated by the feedback loop.

    I suggest a read to the LMP8646 datasheet, which explains in detail how to implement a current source using an existing constant voltage regulator and how to calculate all the required parameters.

    Under the required application, which uses a negative output voltage, the device should be powered from the 5V line and the sense resistor should be placed in series with ground and the negative load as shown below:

    Do be aware that your chosen voltage regulator has a min output of -1.5V, and therefore current throttling will only occur on the range Vout {-1.5...-3.5V}.

    I suggest a device whose output can be adjusted all the way down to zero.

    Kind Regards,

    Carlos S., TI Sensing Products, Applications Support

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.

  • In reply to Carlos Silva85:

    Is this current source we should connect after -3.5V regulator?

    How will it limit the current at 10mA?

    It would be really helpful if you share some connectivity diagram of the complete solution.

  • In reply to RAHUL SHARMA52:

    Hi Rahul,
    Please see my updated post above.

    Kind Regards,

    Carlos S., TI Sensing Products, Applications Support

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.

  • In reply to Carlos Silva85:

    We need to limit current for the following supplies as well ..please suggest regulator compatible with LMP8646 current limiter:

    1. VOUT = +1.8V

    Vin = 3V

    Vout = +1.8V +/-15%

    Current limit power up = 150mA

    Steady State current = 80mA

    Ripple = 30mV RMS @ 1MHZ

    2. VOUT = +6.5V

    Vin = 9V

    Vout = +6.5V +/-5%

    Current limit power up = 100mA

    Steady State current = 80mA

    Ripple = 10mV RMS @ 1MHZ

    For -3.5V current limit as discussed earlier, Can we simulate the full circuit ?
    We got pSpice model for LMP8646 but did not find model for regulator LM27761.
  • In reply to RAHUL SHARMA52:

    Can we use LP38693-ADJ voltage regulator with LMP8646 current limiter to for 1.8V & 6.5V for 150mA current limit ?
    If yes please suggest simulation method
  • In reply to RAHUL SHARMA52:

    The LP38693 has a minimun regulation voltage of 1.25V, therefore the circuit can be implemented to limit current as long as the limitation occurs above this voltage level.

    For Vout >0 and <1.25V the output will be limited by the regulator itself. Please refer to Section 7.3.3 of the device datasheet for further details.

    I would suggest posting a new question on the buck converter forums section for help on choosing an appropriate regulator. In the meanwhile, here is a resource that can help.

    Please note that there will always be a voltage drop across the sense resistor used to monitor the current, so be aware of this when selecting a value so that the output stays within the specifications, when loaded at your desired current level.

    Kind Regards,

    Carlos S., TI Sensing Products, Applications Support

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.

  • In reply to Carlos Silva85:

    As you suggested the LMP8646 for -3.5V@10mA current limiting.
    How to connect Vout pin of LMP8646 to the negative LM27761 regulator Feedback (FB) pin ?
    How we can calculate components for LMP8646 for negative supply since Online tool of LMP8646 is not supporting negative regulator O/P ?
  • In reply to RAHUL SHARMA52:

    Hi Rahul,

    The output of the LMP8646 goes directly into the regulator feedback pin, just as it does on the positive regulator.  Remember both the LMP8646 and the buck boost converter used to generate the negative rail are powered from the positive 5V voltage.

    Kind Regards,

    Carlos S., TI Sensing Products, Applications Support

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.