Communication device with a self-calibrating sleep timer

Abstract

The present invention provides for a system for operating a communication device () for reception of scheduled intermittent information messages () with a dual mode timer () that extends battery life. A controller () schedules the timer () to power down all idle components of the device () between message receptions in a power saving sleep mode to conserve battery power. During active mode when the device is fully active in reception of messages, the timer () uses a reference oscillator () with a relatively high frequency to support digital processing by the receiver (). During sleep mode when only the timer is powered on, a much lower frequency sleep oscillator () is used to maintain the lowest possible level of power consumption within the timer itself. The timer () has provision for automatic temperature calibration to compensate for timing inaccuracies inherent to the low-power low-frequency crystal oscillator () used for the sleep mode. The resultant improvement in timer accuracy during sleep mode eliminates the need for an initial reacquisition period following wake up in active mode, thereby reducing battery drain in active mode as well.