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STMicro RTCs suit camcorders, electronic door locks

Posted: 05 Jul 2004 ?? ?Print Version ?Bookmark and Share

Keywords:stmicroelectronics? serial real-time clock? rtc? m41t50? m41t60?

STMicroelectronics announced three new Serial Real-Time Clocks (RTCs) for use in a broad range of applications from camcorders to electronic door locks.

Providing date and time information over an I?C serial bus, the M41T50, M41T60 and M41T62-65 RTCs all include automatic leap year compensation. They are designed for a bus operating voltage from 3.6V down to 1.3V (M41T50: 1.7V), but will maintain timekeeping at supply levels as low as 1V providing more robust system performance. Operating current is 350?A on a 3V supply, making the RTCs suitable for battery operation and handheld applications. Standby currents will be <650nA at 3V.

Each clock chip offers a mix of operational features that will appeal to different types of applications. The M41T60 and M41T62/63/64/65 series each have built-in 32.768kHz oscillators, used with external crystals, and each includes an Oscillator Stop Detection feature to warn if the recorded time might be corrupted. Software clock calibration allows the host processor to compensate for variations in crystal frequency, and can achieve an accuracy of better than 2ppm at 25C.

Eight BCD (binary coded decimal) registers are used for the clock/calendar function, with additional registers used for status and control. The M41T60 provides crystal controlled time-of-day clock and calendar, while the M41T62/63/64/65 series adds a watchdog timer and various combinations of alarm interrupt, 32kHz output, programmable squarewave output and watchdog output.

The M41T50 operates from either a 50Hz or a 60Hz input which can be derived from line power. In addition to the time-of-day clock and calendar, user functions include a programmable alarm interrupt, and a 1Hz square wave output which minimizes the need for external circuitry.

Operating between the -40C to 85C temperature range, the M41T50, M41T60 and M41T62-65 RTCs are priced at 40 cents, 45 cents and 50 cents, respectively, and are available in a lead-free 16-pin QFN package.

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