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AMC3302: Application questions about AMC3302

han zheng
Prodigy 30 points
Part Number: AMC3302

Tool/software:

Hello, regarding the application of AMC3302, we as above FB1 used spec 182 beads (BLM15HD182SH1) as recommended in the datasheet, R2=R4=100R, shunt=0.1mΩ.
We have the following problem in the application process:
In some high-frequency voltage oscillating conditions, the current through the shunt is 0A, but the shunt In some high-frequency voltage oscillation conditions, the current through the shunt is 0A, but the voltage of the shunt has 100-300kHZ high-frequency jitter, and at this time, the V (OUTP-OUTN) is abnormally high (>3V) for about 10us.
We did the following
Measure 1: Keep FB1/FB2, change FB3 to 0R resistor, V (OUTP-OUTN) ≈ 0V, normal.
Measure 2: Keep FB3, change FB1/FB2 to 0R resistor, V (OUTP-OUTN) ≈ 0V, normal.
The test data is as follows

May I ask.

Q1: What is the principle of measure 1 and measure 2?

Q2: Is it possible to remove the magnetic bead or adjust the parameters?

Q3: What are the resistance values of the following 5 resistors?

  • 0
    TI__Expert 5410 points

    Hi Han,

    Can you provide some information about your application?

    han zheng said:
    Q1: What is the principle of measure 1 and measure 2?

     My guess is that the high frequency noise is not hitting the ferrite beads at the same time, causing there to be a voltage between the input pins. The odd thing is that the output's shouldn't reach >3V ever. How are you measuring the output pins?

      Could you share your schematic and layout?  

    han zheng said:
    Q2: Is it possible to remove the magnetic bead or adjust the parameters?

    The ferrite beads are there for EMI.  Since our device has an internal DCDC, the noise from the DCDC can couple to the inputs. Any long traces/cables could act as antennas and radiate the DCDC frequency.  What type of EMI testing/ requirements does your system have? 

    han zheng said:
    Q3: What are the resistance values of the following 5 resistors?

    I'm not sure what the exact values are, but the single ended and differential impedance of those pins are as follows:

    Thanks.