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STMicroelectronics Introduces Real-Time Clock Chips To Widen Designers' Price and Performance Choices |
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 Geneva, October 8, 2001 - STMicroelectronics (NYSE: STM) announces two serial real-time clock (RTC) chips, expanding the company's M41Txx family of microprocessor supervisor ICs. Of the two introductions, the feature-rich M41T94 touts an RTC accessible via a Serial Peripheral Interface (SPI), power-on-reset/low-voltage detector, low-battery monitor, programmable alarm and interrupt function, watchdog timer, push-button microprocessor reset, and non-volatile RAM. The second of the two introductions, the M41T81, stresses small size and high value, and includes an RTC, programmable alarm and interrupt function, and watchdog timer. As part of their protective functions, both the M41T94 and M41T81 switch automatically to an optional external lithium battery should power fail, providing a write-protect function in the process for added reliability. Typical targets for both RTCs include DVD players, metering and medical equipment, point-of-sale terminals, and virtually any device that contains a microcontroller or microprocessor. First and foremost among the chips' features is an RTC that makes available to the user, in binary-coded decimal (BCD) format, the present time from the century to tenths and hundredths of a second. The clock operates from a 2.0V (2.7V for the M41T94) to 5.0V supply and uses a built-in 32.768kHz oscillator and external crystal. In addition, the M41T94's power-on-reset/low-voltage detector and low-battery flag can be set to trigger microprocessor reset signals at one of two voltage points. Specifically, with the chip's voltage threshold input tied to the supply voltage, VCC, the chip's power-fail deselect function activates if the voltage drops to 4.40V±0.10V. Alternatively, the power-fail deselect function can be set to activate at 2.65±0.05V by connecting the chip's threshold input to ground, VSS. Of the functions that both chips have in common, like the programmable alarm, watchdog, and square-wave functions, the alarm has repeat and battery back-up modes, the watchdog interval can be set from 62.5ms to 128s, and the square-wave frequency is adjustable from 1Hz to 32kHz. Communication with M41T94 is done over its synchronous SPI bus. For the M41T81, communication is over a 400-KHz Inter-IC (I2C) bus. Another feature of the M41T94 is its two power-on reset inputs, which issue a reset pulse output if either is active. Of the two inputs, one is de-bounced for pushbutton operation. In all, the M41T94 offers five sources for generating a reset: the two reset inputs, during power-on and low-voltage conditions, and from its watchdog timer. The M41T94 also has 64 bytes of memory space comprised of 20 bytes for the RTC registers and 44 bytes for general-purpose use. To meet power budgets and extend battery life, both the M41T94 and M41T81 use power sparingly. Specifically, the M41T94 operates from 2.7 to 5.5V and draws 2.0mA from the supply, which falls to 500nA under battery power. The M41T81 operates from 2.0 to 5.5V and draws just 400µA of supply current. Moreover, that current flow drops to a mere 1µA under battery operation. The M41T94 comes in a 16-pin SOIC. It also is available in the 28-pin SNAPHAT® SOIC package for use with STMicroelectronics' SNAPHATÒ Battery and Crystal top. The M41T81 comes in an SO-8 package. Both chips are specified over the industrial temperature range of -40° to +85°C. Additional information for these and other STMicroelectronics RTC devices is available at www.st.com/nvram. About STMicroelectronics STMicroelectronics is the world's third largest independent semiconductor company. The Company shares are traded on the New York Stock Exchange, on Euronext Paris and on the Milan Stock Exchange. The Company designs, develops, manufactures and markets a broad range of semiconductor integrated circuits (ICs) and discrete devices used in a wide variety of microelectronic applications, including telecommunications systems, computer systems, consumer products, automotive products and industrial automation and control systems. In 2000, the Company's net revenues were $7,813.2 million and net earnings were $1,452.1 million. Further information on ST can be found at www.st.com. |
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