bq4847Y

The bq4847 Real-Time Clock Module is a low-power microprocessor peripheral that integrates a timeof-day clock, a 100-year calendar, a CPU supervisor,a battery,and a crystal in a 28-pin DIP module. The part is ideal for fax machines, copiers, industrial control systems, point-of-sale terminals, data loggers, and computers.


The bq4847 contains an internal battery and crystal.Through the use of the conditional chip enable output (CEOUT) and battery voltage output (V_OUT) pins, the bq4847 can write-protect and make nonvolatile an external SRAM. The backup cell of bq4847Y powers the real-time clock and maintains SRAM information in the absence of system voltage.


The bq4847 contains a temperature-compensated reference and comparator circuit that monitors the status of its voltage supply. When an out-of-tolerance condition is detected, the bq4847 generates an interrupt warning and subsequently a microprocessor reset. The reset stays active for 200ms after VCC rises with in tolerance to allow for power supply and process or stabilization.


The bq4847 also has a built-in watchdog timer to monitor processor operation.If the microprocessor does not toggle the watchdog input (WDI) within the programmed time-out, the bq4847 asserts WDO and RST. WDI unconnected disables the watchdogtimer.


The bq4847 can generate other interrupts based on a clock alarm condition or a periodic setting. The alarm interrupt can be set to occur from once per second to once per month. The alarm of bq4847Y can be made active in the battery-backup mode to serve as a system wake-up call. For interrupts at a rate beyond once per second, the periodic interrupt can be programmed with periods of 30.5 s to500ms.