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INA240: Survey TI CSM & Protection Solution

Part Number: INA240

Hi Team,

I plan use TI device implement CSM & protection function. Could provide your suggestion for me? thanks.

Test condition

Accuracy 5% - 10% @Light load 500mA

Accuracy 2% - 5% @Heavy load 45A (peak load transient 75A)

Bus Voltage 4.5VDC - 7VDC

1. Looks INA240 with shunt resistor 1m ohm have good performance. Am I right?

2. In my system, current is dynamic load since we have PWM control LED panel. so input current behavior is not average.

we need RMS converter DC out for MCU implement protect. such as ADI device AD8436 & AD637 has RMS to DC function.

IMin_Load 5 A Minimum Load Current
IMax_Load 75 A Maximum Load Current
Gain 50 V/V  
RShunt 0.0010667 Ω Sense Resistor
Vmin_out 0.0053333 V Minimum VOUT
Vmax_out 4 V Maximum VOUT
ADC full scale 4.096 V Full-Scale Load Current (VOUTMAX)
RPD 6 W Resistor Power Dissipation

  • Wen Yung,

    1. The INA240 is an excellent choice for this application. The fast-common mode rejection is directly suited to PWM drives. From the details you posted above, the 1mOhm resistor is a good choice to take advantage of most of the output range of the INA240. What is the power supply for the INA240, and do you happen to know at what frequency the PWM will switch?

    2. I've done some searching and I don't believe TI has a monolithic RMS-to-DC product. I'm still looking around for options but I am pretty sure TI doesn't have anything to offer here yet.

    Best Regards,

    Jason Bridgmon, TI Sensing Products Applications Support

    Current Shunt Monitor Video Training Series

    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 Jason Bridgmon:

    Hi Jason,

    PWM frequency around 4~16MHz depends on application modify and PWM Cycle <26us.

    Wen
  • In reply to Wen Yung:

    Wen,

    Thank you for the information.  I'm a little unclear about the PWM though - you said it operates at up to 16MHz, but then said it has a cycle of <26uS, which is just around 38kHz.  38kHz is well within the bandwidth of the INA240, but 16MHz is too fast.  Could you help me understand?

    Best Regards,

    Jason Bridgmon, TI Sensing Products Applications Support

    Current Shunt Monitor Video Training Series

    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 Jason Bridgmon:

    Hi Jason,

    38kHz for PWM and resolution scale 1024 ~ 4096bit.
    so per step response is 25.4ns~6.348ns .
  • In reply to Wen Yung:

    Wen,

    As you modify the duty cycle of the PWM, you need to be aware that if you have pulses that are less than roughly 10uS (about 40% duty cycle at a 38kHz PWM) then you might have issues as the output might not settle in time for the measurement. It would also act like a filter to remove any glitches you might want to see on the waveform.

    Just something to be aware of with your design.

    Best Regards,

    Jason Bridgmon, TI Sensing Products Applications Support

    Current Shunt Monitor Video Training Series

    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.