ADM1085 Leakage/Pulse when Initial Stage

Question

Hi ADI Expert, 
 Is normal to see pulse / leakage at ADM1085's ENOUT ? 
 Due to ENOUT is open-drain and this pin is puled high to Vcc. 
 So before ADM1085 finish initial setting, ENOUT will rise with Vcc. 
 I also found a describtion in AN-1080 : 
 "In a system where a brief pulse of the first supply, during initial power-up, does not cause any problems, it is recommend to use VIN only for the circuit supply."

ADIApproved · Accepted Answer

Hi Henry, 
 The reason there is a pulse at power up is because both Vcc and ENOUT pull-up is connected to the same supply. Before the supply voltage crosses the UVLO of the ADM1085, ADM1085 is not actively driving the ENOUT. 
 Would it be possible to connect the Vcc and ENOUT to two different supplies where supply connected to Vcc comes up before the pull-up supply.)

Partner Forums

Partner Libraries

Products Mentioned

ADM1085 Leakage/Pulse when Initial Stage