AD5560 Force Current Limit issue


I am now testing the AD5560 Eval Borad. An external load is connected and test the output of the current. A current of about 300 mA  more is not output(less than 300mA Current output OK). The current clamp is not used and the measured value is less than the set voltage value when the MEASOUT pin is set to VSENSE while outputting 300mA (the measured voltage value is measured according to the set value at output of 300mA or less)

The power supply was connected to AVDD / HCAVDD = + 12V (22A), AVSS / HCAVSS = -12V (0.3A) and DVCC = + 3.3V (20A). Current Range is set to EXT1 Current Range.

I would like to know if the current of 300mA or more is not outputted because the input current of -12V is small.

Thank you.

  • Hi dcmoon,

       Just a few clarifications for me to better understand the problem.

          1. What force voltage did you place in the FIN DAC? Is that the same voltage you see across your external load?

          2. You are Using EXT1 Current Range Correct? What Value is your Ext. Rsense1 and external load?

          3. Are you using the customer software?

          4. Could you provide a simple block diagram of what your are doing on the eval board?

       From what I understand, you are trying to force a voltage but you are not seeing it go beyond 300mA, this would be true if you are going in the negative range and forcing more than AVss(-12V)+1.75V + Vrsense. Where 1.75V is the headroom and Vrsense(should be at most 500mV) is the drop across your EXT Rsense1. This is the max voltage range you could go to ensure linearity. If this is the case you are just hitting the negative rail of the part and what you could do is increase the AVss. Also please note that in Page 11 of the AD5560 Datasheet Rev. E, Power Supplies section, HCAIss1 should have an added allowance of -20mA apart form the intended load conditions.  

    Best Regards,