Method and Apparatus for Real Time Clock (RTC) Brownout Detection
1 Assignment
0 Petitions
Accused Products
Abstract
A method and apparatus for real time clock brownout detection. A low power real time clock (RTC) operates continuously to keep time in a global positioning system (GPS) receiver while some receiver components are powered down. In various embodiments, a brownout detector circuit detects a loss of RTC clock cycles. If a loss of RTC clock cycles exceeds a predetermined threshold such that the RTC is not reliable for GPS navigation, an RTC status signal so indicates.
-
Citations
47 Claims
-
1-28. -28. (canceled)
-
29. A method of determining of a real time clock (“
- RTC”
) in a global positioning system (“
GPS”
) receiver system is accurate enough to be used on start up of the GPS receiver, the method comprising;Transferring the time kept by the RTC clock to a GPS clock of the GPS receiver system; Estimating the position of visible satellites, wherein the GPS clock is updated with signals from the RTC clock; Based on the estimated position of the visible satellites, measuring a pseudo-noise (“
PN”
) code for each of the visible satellites;Calculating an expected current full PN code phase for each of the visible satellites; Computing the location of the GPS receiver using the expected current full PN code phases; Comparing the computed location of the GPS receiver to a previously-computed location of the GPS receiver in units of time;
determining whether the computed location of the GPS receiver has changed more than a predetermined threshold amount exceeding the predetermined threshold amount, establishing a new GPS clock by acquiring the visible satellites using conventional methods. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36)
- RTC”
-
37. A method of updating a real time clock (“
- RTC”
) in a global positioning system (“
GPS”
) receiver system that uses significantly less power than a GPS clock of the GPS receiver system, the method comprising;receiving a wake up command at a GPS receiver of the GPS receiver system while the GPS the GPS receiver is in a powered down mode; powering up selected components of the GPS receiver in response to receiving the wake up command; measuring an operating temperature of the RTC of the GPS receiver; calculating a frequency error associated with the RTC based upon the measured operating temperature of the RTC; updating the RTC with the frequency error; and powering down the selected components of the GPS receiver. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
- RTC”
Specification