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DEMO-5700D2Z: AD5421 unexpected current in loop

Hello,

I just bought DEMO-5700D2Z board and was verifying the functionalities. Last week I dumped the demo code provided, the current loop was varying from 4mA to 20mA as expected. But when I dumped the same code today, the current loop is as high as 80mA. I checked loading a different code (just to blink an LED) but still the current is above 80mA. I disconnected the rest of the circuitry from AD5421 and saw that it still took 80mA. Fault pin is high. I measured the voltage between COM and LOOP-, which was 4.47V implying almost 86mA is flowing through the 52ohm resistance inside the chip.

But I'm unable to locate what the exact problem is. Could anyone throw some light on what might the error be and what other parameters I should be checking?

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  • Hi Rainier,

    Yes, the voltage regulator is still working properly and there is no short between -LOOP and COM pins. Thus I'm unable to conclude what might have gone wrong. I will wait to receive new set of ICs and get back to you on this.

    Thanks for clarifying. So, I can draw max of 3.15mA at 12V REGOUT (other pins unused). I'm planning to then use a separate buck converter(say, ADP2360) to bring the voltage down to 3.3V and draw higher current of 8mA (assuming 80% efficiency). Is this possible or do you see any error in this?

    Thanks,

    Spoorthy

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  • Hi Rainier,

    Yes, the voltage regulator is still working properly and there is no short between -LOOP and COM pins. Thus I'm unable to conclude what might have gone wrong. I will wait to receive new set of ICs and get back to you on this.

    Thanks for clarifying. So, I can draw max of 3.15mA at 12V REGOUT (other pins unused). I'm planning to then use a separate buck converter(say, ADP2360) to bring the voltage down to 3.3V and draw higher current of 8mA (assuming 80% efficiency). Is this possible or do you see any error in this?

    Thanks,

    Spoorthy

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