September 12, 1997

Simple regulator monitors its input voltage

Larry Suppan and Luong Huynh, Maxim Integrated Products, Sunnyvale, CA

Two- and three-cell portable systems, such as medical sensors, often monitor their battery input to obtain an early warning of a loss of battery voltage. Typically, this warning is a digital signal that a comparator generates and then sends to the microcontroller. The circuit in Figure 1 presets one side of a dual linear regulator to generate 2.84V at 100 mA. The other side operates open loop, as a comparator, to generate the low-battery warning. Both sides are capable of delivering 100- mA output current. Resistors R₁ and R₂ determine the low-battery threshold, according to

(DI #2089)

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