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High speed current sensing

Nic
Prodigy 80 points
Part Number: INA260
Other Parts Discussed in Thread: INA293, INA180

Hi TI team,

I am looking for a high speed current sensing part that have below features:

1. Input signal: 100MHz, 6A current signal

2. Able to detect peak current or average current

Do you have any recommendation? Thanks.

Regards,

Nic

  • 0
    Guru 244050 points

    Your other post implies that you want to build a fuse circuit.

    Low-side or high-side sensing? What accuracy is needed?

    Does "100 MHz" imply that you want to trigger on a current pulse with a length of 10 ns? There is no integrated current monitor that is that fast.

    Do you want to limit the current or switch off? In the first case, you need a high-speed amplifier (see page 37 of the Simplifying Current Sensing white paper); in the latter case, you probably need a high-speed comparator.

  • 0
    Guru 140200 points

    Hi Nic,

    many more details are required. Best you could show a schematic.

    Kai

  • 0 in reply to Clemens Ladisch
    Prodigy 80 points

    What I am looking for looks like this:

    The 100MHz/50% duty cycle signal drives a switch to convert the current to RL. The current flowing RL is a 100MHz/50% signal as well. I want to monitor and record the RL average current in real time. (Monitoring peak current seems impossible). Required accuracy is 0.1A. 

  • 0 in reply to Nic
    Guru 244050 points

    Current monitors are limited by the communication protocol (SPI or I²C), so their bandwidth is at most a few kHz.

    Current sensors have an analog output (and sometimes a comparator output if you want to quickly handle overcurrents with an interrupt). You'd need an ADC to read them. It would be possible to add a peak detector circuit with another opamp.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 18780 points

    Nic,

    I'm in agreement with Clemens here. If you need bandwidth above a few hundred kilohertz, you will most likely need a high speed op amp to perform this task (given that you only want to measure average current, I don't know how much BW you need). The fastest current sense amplifier we have in our portfolio is INA293, which tops out at 1.3MHz for the A1 version. 

    With your schematic as set up, you will also need to ensure that you select a device that is capable of accepting 6.5V for V+ for the device to be able to withstand the common mode voltage on the high side. There is more information regarding this here. 

    I'm looping in our high speed team to get their thoughts as well. 

  • 0 in reply to Carolus Andrews
    Prodigy 80 points

    Yes, I only want to monitor the average current. The average current should be considered as DC, so the bandwidth should be closed to DC, I think. The current sensing amp could be regarded as the low-pass filter. 

    For 6A peak current, 50% duty cycle signal, the average current is 3A.

    From this standpoint, I think most of the TI parts could fit that, right?

  • 0 in reply to Nic
    Guru 140200 points

    Hi Nic,

    what voltage drop would be seen across Rsensing?

    Kai

  • 0 in reply to Nic
    TI__Mastermind 18780 points

    Nic,

    If you only need to measure average current, then yes, I agree, most parts in our portfolio should meet your needs. If you do find that you need the additional BW though, I would check with our high speed amplifiers forum for additional recommendations.

    I would recommend having a look at our INA180, which still has a high bandwidth and is cost-optimized for several different types of applications (350khz).