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Problems using an AD5170 to control a LDO

Question asked by alkrojen on May 11, 2011
Latest reply on May 11, 2011 by LWong

Dear Analog experts


I am having some problems using your AD5170BRMZ50 I2C potentiometer.

When the potentiometer terminals are not connected it works fine and I can adjust the resistance by I2C.


But when the device is connected to the LDO (LP3875-ADJ) without having the LDO turned on or having voltage on the input side of the LDO.

The resistance suddenly measures several mega ohms.


AD5170BRMZ50 is connected to the LP3875-ADJ as the R1 and R2 voltage divider illustrated in the datasheet of the LP3875-ADJ.

when I disconnect the AD5170BRMZ50 from the LDO it still measures many mega ohms, for a while (1 hour). Even if I cycle the power on and off several times. After then it apears that the resistance is back to Rwa=25K Rwb=25K (initial condition)


What can be wrong?

The AD5170BRMZ50 is supplied a battery voltage of 3,7 V.


Looking forward to your reply


best regards