Wireless Systems Design

Real-Time Clock IC Cuts Current Consumption

In handheld devices, energy efficiency is critical. To help designers achieve that efficiency, Seiko Instruments has come out with the S-35180A and S-35380A Series ICs. These ICs promise to provide ultra-low current consumption for real-time clocks. As a result, they are well suited for applications like MP3 players, digital cameras, digital video cameras, handheld games, mobile phones, and home security systems.

The integrated circuits' low quiescent current of 0.25 µA greatly increases battery operation. The S-35180A and S-35380A Series ICs also promise to be high-accuracy, high-performance devices. They have a minimum time-keeping voltage operation of 1.1 V and a wide operating range of 1.3 to 5.5 V.

A notable feature of the ICs is their clock-adjustment function. This function enables the wide-ranging correction of deviation in the frequency crystal oscillator at a minimum resolution of 1 ppm. When this function is combined with a temperature sensor, the clock adjustment value can be set in accordance with changes in the temperature. It is therefore possible to realize a clock function that will retain a high degree of accuracy regardless of temperature fluctuation.

For systems that operate on a backup battery, an integral free register in the real-time clock 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 1.2 V. It stores the data in the register before the main power supply is cut off. This feature permits the data to be recalled anytime after the voltage is restored.

The series S-35180A IC is available in a three-wire CMOS (micro-wire) CPU interface. The S-35380A IC is available in a two-wire CMOS (I2C-bus) CPU interface. In quantities of 10,000, the S-35180A and S35380A are priced from $0.60 (8-pin SOP) and $0.65 (8-pin TSSOP).

Seiko Instruments, Inc.
8, Nakase 1-chome, Mihama-ku, Chiba-shi, Chiba 261-8507, Japan; +81 43 211 1111, www.sii-ic.com.

TAGS: Mobile
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