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ADCMP350 Vcc=0 V+>0

Question asked by quentis on Oct 3, 2015
Latest reply on Oct 13, 2015 by quentis

I have to supply rails: an adapter AC/DC and one USB. They are ORed together through diodes. I want to support 5V adapters (if it is connected the USB power is turned off) so if the voltage is greater than 4.5V on the adapter side I disable the USB power through a switch. ADCMP350 is powered from the USB side but the input is tied to the adapter side. However there might be a situation where the USB is not connected but the adapter is. In this case the device is not powered however the input is driven (high resistance - resistor divider).

 

I have the following question: what happens if ADCMP350 comparator is not supplied but there is some voltage through a resistor divider in its non-inverting input? Will be the output determined? Can I damage the device in this way?

According to the datasheet in normal conditions the input voltage can be much more greater than the supply but I don't know if it is true when the power is off.

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