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STMicro RTC/supervisor IC features own crystal

Posted: 06 Mar 2003 ?? ?Print Version ?Bookmark and Share

Keywords:stmicroelectronics? m41st85? m41st85mx6? m41st85mh6? rtc ic?

STMicroelectronics has announced a new version of its M41ST85 serial real-time clock (RTC) and supervisor chip that packs a 32kHz crystal into an 18.4-by-10.42-by-2.4mm SOX28 package.

By integrating the crystal into the package, the company said that a better match can be achieved between the IC and the crystal, thereby improving timekeeping accuracy. The package also offers enhanced security by isolating the crystal from tampering, as well as shielding it from humidity.

The M41ST85MX6 is available in 3V and 5V versions, and operates over the industrial temperature range of -40C to 85C. It is designed for use in POS terminals, servers, medical systems, vending machines, SCSI peripherals, and arcade and other computer games.

Similar to the company's previous M41ST85MH6 device, the M41ST85MX6 combines a serial RTC with Microprocessor and NVRAM SUPERVISOR functions. The programmable, battery-backed RTC section contains counters that track time and date with resolution ranging from hundredths of a second up to the century. It is accessed via a 400kHz I?C interface.

Built using low-power CMOS SRAM technology, the RTC section is organized as 64-by-8 bits, of which 44 bytes are general-purpose NVRAMs, while the remaining 20 bytes are the RTC registers.

The NVRAM SUPERVISOR section can be used to "non-volatize" a low power SRAM. Its functions include an automatic battery switch-over circuit, a chip-enable gate for write protection, and a battery monitor. This enables the user to create an NVRAM by using the M41ST85MX6's back-up battery to also back-up the LPSRAM.

The microprocessor SUPERVISOR section includes an early power-fail warning circuit, with a 1.25V reference, and a reset circuit, which can be triggered by multiple sources (including two reset input pins and a power-on reset/low-voltage detect circuit). The watchdog can also be configured as a reset source, and is programmable for timeout periods ranging from 62.5ms to 128s.

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