Analog Devices Inc./Maxim Integrated

The DS1321 Flexible Nonvolatile Controller with Lithium Battery Monitor is a CMOS circuit which solves the application problem of converting CMOS SRAMs into nonvolatile memory. Incoming power is monitored for an out-of-tolerance condition. When such a condition is detected, chip enable outputs are inhibited to accomplish write protection and the battery is switched on to supply the SRAMs with uninterrupted power. Special circuitry uses a low-leakage CMOS process which affords precise voltage detection at extremely low battery consumption. One DS1321 can support as many as four SRAMs arranged in any of three memory configurations.In addition to battery-backup support, the DS1321 performs the important function of monitoring the remaining capacity of the lithium battery and providing a warning before the battery reaches end-of-life. Because the open-circuit voltage of a lithium backup battery remains relatively constant over the majority of its life, accurate battery monitoring requires loaded-battery voltage measurement. The DS1321 performs such measurement by periodically comparing the voltage of the battery as it supports an internal resistive load with a carefully selected reference voltage. If the battery voltage falls below the reference voltage under such conditions, the battery will soon reach end-of-life. As a result, the Battery Warning pin is activated to signal the need for battery replacement.

The DS1330 256k Nonvolatile (NV) SRAMs are 262,144-bit, fully static, NV SRAMs organized as 32,768 words by 8 bits. Each NV SRAM has a self-contained lithium energy source and control circuitry which constantly monitors VCCfor an out-of-tolerance condition. When such a condition occurs, the lithium energy source is automatically switched on and write protection is unconditionally enabled to prevent data corruption. Additionally, the DS1330 devices have dedicated circuitry for monitoring the status of VCCand the status of the internal lithium battery. DS1330 devices in the PowerCap module package are directly surface mountable and are normally paired with a DS9034PC PowerCap to form a complete NV SRAM module. The devices can be used in place of 32k x 8 SRAM, EEPROM, or Flash components.

The DS1337 serial real-time clock is a low-power clock/calendar with two programmable time-of-day alarms and a programmable square-wave output. Address and data are transferred serially through an I²C bus. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator.The device is fully accessible through the serial interface while VCCis between 1.8V and 5.5V. I²C operation is not guaranteed below 1.8V. Timekeeping operation is maintained with VCCas low as 1.3V.ApplicationsConsumer Electronics (Set-Top Box, VCR/Digital Recording)Handhelds (GPS, POS Terminal, MP3 Player)Medical (Glucometer, Medicine Dispenser)Office Equipment (Fax/Printer, Copier)Other (Utility Meter, Vending Machine, Thermostat, Modem)Telecommunications (Router, Switcher, Server)

The DS1339A serial real-time clock (RTC) is a low-power clock/date device with two programmable time-of-day alarms and a programmable square-wave output. Address and data are transferred serially through an I²C bus. The clock/date provides seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The DS1339A has a builtin power-sense circuit that detects power failures and automatically switches to the backup supply, maintaining time, date, and alarm operation.ApplicationsConsumer Electronics (Set-Top Box, Digital Recording, Network Appliance)Handhelds (GPS, POS Terminals)Medical (Glucometer, Medicine Dispenser)Office Equipment (Fax/Printers, Copier)Other (Utility Meter, Vending Machine, Thermostat, Modem)Telecommunications (Routers, Switches, Servers)