Q&A

摘要

Q There was a Q&A reprint in a recent N&V newsletter titled Low Battery Indicator. Regarding the circuit shown in figure 1, it states "The circuit draws a mere 120 microamps, which is just slightly more than the self-discharge current of the same battery sitting on a shelf." I am not sure this is correct. I calculate that at nine volts the threshold adjustment divider will consume 37 microamps, the reference divider 43 microamps, and from the spec sheet, Icc typical for the comparator is 60 microamps. This all adds up to 140 microamps, which is reasonably close to the 120 microamp figure. According to Duracell, the capacity of an MN1604 battery at low drain rates is about 600 milliamp hours. If you divide 600 mAh by 140 microamps, you come out with a battery lifetime of about 4285.7 hours, which is about a half a year.