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Original question:

AMC3330: Suggested suitable configurations for current measurement using current transformers

AMC3330: AMC3330

sapana darekar
Prodigy 20 points
Part Number: AMC3330
Other Parts Discussed in Thread: AMC3302, AMC3301, AMC23C12

Tool/software:

Hi,

According to the document titled Shunt-Based, 200-A Peak Current Measurement Reference Design Using Reinforced Isolation Amplifier (Rev. A).

we need to determine whether an instrumentation amplifier is necessary before the AMC3330 when utilizing this amplifier in conjunction with a shunt.

We aim to measure a current range of 1A to 425A RMS (with a peak of 600A) using a 500µΩ shunt.

However, the input ranges of the AMC3301 (+/-250mV) and AMC3302 (+/-50mV) do not meet our requirements due to their limited input capabilities.

Is it possible to connect the shunt directly to the AMC3330 amplifier?

Current Range: 1A to 425A AC (600A peak)

Voltage Drop: 0.5mV to 300mV

Amplifier: AMC3330

with a gain of 2 Output Voltage: 1mV to 600mV

  • 0
    TI__Guru 55662 points

    Hi Sapana, 

    425Arms with a 500uOhm shunt is 90.3W, which for many applications is beyond tolerable heat dissipation. I would expect most applications to instead use a smaller value shunt, perhaps 50uOhm which would then pair nicely with the 50mV input voltage range of the AMC3302. 

    For my curiosity, can you share some additional details about your application? 

    As to your question, this is absolutely fine to connect the shunt directly to the AMC3330 amplifier. Most often, we would recommend connecting INN and HGND to to one side of the resistive element and INP to the other side of the resistive element. 

    While our EVM is not rated for high voltage operation you could use a signal generator to verify this performance: https://www.ti.com/tool/AMC3330EVM

    If a fast over-protection is necessary, please consider our AMC23C12, powered from the AMC3330 HLDO_OUT (with 5V VDD) as shown on this EVM where the AMC3302 could be replaced with an AMC3330: https://www.ti.com/tool/AMC-AMP-50A-EVM

  • 0 in reply to Alexander Smith
    Prodigy 20 points

    Thank you, Alexander Smith.

    The 425A measurement does not represent continuous current, as continuous current is limited to 60A. However, one of the criteria requires us to measure up to 425A for a brief duration without experiencing saturation.

    The shunt voltage drop reaches 300mV peak at 425A AC RMS, which is not compatible with the AMC3301. Therefore, we are considering the AMC3330 as an alternative.

    I will go through the AMC23C12.

  • 0 in reply to sapana darekar
    TI__Guru 55662 points

    Thank you for the feedback Sapana. Please let me know if you have any questions.