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Maxim > Design Support > Technical Documents > Application Notes > Microprocessor Supervisor Circuits > APP 608
Keywords: automatic shutdown, automatic power-up, automatic low battery lockout, battery disconnect,
load disconnect, power up
APPLICATION NOTE 608
Micropower Circuit Offers Automatic Shutdown
and Low-Battery Lockout
Jun 01, 2001
Abstract: The following application note provides a circuit that automatically performs shutdown, power-
up, and low-battery lockout functions without the need for software control.
This micropower circuit provides shutdown, power-up, and low-battery lockout functions automatically,
without the need for software or operator control (Figure 1). Featuring 2.3V hysteresis, the circuit
eliminates the use of microprocessor I/O pins for charger detection, battery-threshold monitoring, and
shutdown control. Under full load, the complete power-management circuit draws less than 200µA of
supply current.
Figure 1. This micropower circuit provides shutdown, power-up, and low-battery lockout functions for this
three-cell NiCd-based circuit without the need for software or operator control.
After the cutoff point for battery discharge is reached, the circuit locks out (disconnects) the battery from
the load (Load1). This action prevents circuit "chatter" and deep discharge until the battery is in its
charger cradle. A common and annoying problem with battery-voltage monitors, chatter is the circuit's
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