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Clocks retain accuracy

Posted: 25 Nov 2005 ?? ?Print Version ?Bookmark and Share

Keywords:Seiko Instruments? real time clock? rtc? S-35190A? S-35390A?

Seiko Instruments' real time clocks (RTCs) feature low current consumption for MP3 players, digital cameras, digital video cameras, handheld games, mobile phones and home security systems. The S-35190A and S-35390A RTC ICs offer ultra-low quiescent current of 0.25?A, and have a minimum time keeping voltage operation of 1.1 V and a wide operating range of 1.3V to 5.5V.

Seiko's clocks also feature a clock adjustment function that enables wide ranging correction of deviation in the frequency crystal oscillator at a minimum resolution of 1ppm. When this function is combined with a temperature sensor, the clock adjustment value can be set in accordance with changes in the temperature, making it possible to realize a clock function that will retain a high degree of accuracy regardless of temperature fluctuation, according to the company.

For systems that operate on a backup battery, an integral free register in the RTC may be used for a backup memory function. This security function allows the user register to hold data on a supply voltage as low as 1.2V, thereby storing the data in the register prior to the cut off of the main power supply. This feature permits the data to be recalled any time after the voltage is rerestored.

Seiko's S-35190A IC is available in a 3-wire CMOS (micro wire) CPU interface, whereas the S-35390A IC is available in a 2-wire CMOS (I?C bus) CPU interface. The S-35190A and S-35390A are priced from 60 cents (8-pin SOP) and 65 cents (8-pin TSSOP) in 10,000-piece quantities.

- Bettyann Liotta

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