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AMC1300B-Q1: AMC1300B output gain unstable when input is low.

Racheal Shen
Prodigy 121 points
Part Number: AMC1300B-Q1

Tool/software:

Hi there,

My customer InfyPower tested AMC1300B and find that the gain of voltage is not stable, which should be 8.2 in all input range. The schematic is shown below. Note that a 2mohm sampling resistor is connected between DCCURRSAMP2 and GND used to test the BUS current, this is not shown in the figure but referred by the customer.

Schematics

Test process: The customer connect VIN+ & VIN- directly to signal generator, and tune the input voltage. Scope the output voltage VOUT+ to VOUT-.

Test results: The results are in the second figure. 1-3 column is input voltage, AMC1200B output voltage, AMC1300B output voltage. It seems that AMC1200B is more precision in amplifying. And AMC1300B error is quite large when the input is low. But the problem is that AMC1300B is designed to perform better by datasheet.

Can you point out the reason for AMC1300B’s performance? Is it normal operation? Thanks a lot.

test result

  • 0
    TI__Expert 6015 points

    Hi Racheal,

    Thank you for your question. The AMC1300B should have better performance than the AMC1200B. However, the AMC1300B would not have a need for the two diodes on the input as your customer has in their schematic. 

    For the AMC1200B, these diodes would be beneficial since the input bias current changes with the input voltage. The AMC1300B in contrast has a constant input bias current, so adding these diodes would have adverse effects at these low voltages. Therefore, I'd recommend they remove these diodes if they want to use the AMC1300B. 

    Also, do you know how the customer measures their data shared? Please let me know if this improves their circuit or if there are any other questions. 

    Best regards,

    Eva