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BQ4845S- Datasheet(PDF) 3 Page - Texas Instruments |
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BQ4845S- Datasheet(HTML) 3 Page - Texas Instruments |
3 / 22 page Pin Descriptions X1–X2 Crystal inputs X1–X2 are a direct connection for a 32.768kHZ, 6pF crystal. RST Reset output RST goes low whenever VCC falls below the power fail threshold. RST will remain low for 200ms typical after VCC crosses the threshold on power-up. RST also goes low whenever a watchdog timeout occurs. RST is an open- drain output. INT Interrupt output INT goes low when a power fail, periodic, or alarm condition occurs. INT is an open-drain output. WDI Watchdog input WDI is a three-level input. If WDI remains either high or low for longer than the watchdog time-out period (1.5 seconds de- fault), WDO goes low. WDO remains low until the next transition at WDI. Leaving WDI unconnected disables the watchdog function. WDI connects to an internal volt- age divider between VOUT and VSS, which sets it to mid-supply when left uncon- nected. WDO Watchdog output WDO goes low if WDI remains either high or low longer than the watchdog time-out period. WDO returns high on the next tran- sition at WDI. WDO remains high if WDI is unconnected. A0–A3 Clock address inputs A0–A3 allow access to the 16 bytes of real- time clock and control registers. DQ0–DQ7 Data input and output DQ0–DQ7 provide x8 data for real-time clock information. These pins connect to the mem- ory data bus. VSS Ground CS Chip select OE Output enable OE provides the read control for the RTC memory locations. CEOUT Chip enable output CEOUT goes low only when CEIN is low and VCC is above the power fail threshold. If CEIN is low, and power fail occurs, CEOUT stays low for 100 µs or until CEIN goes high, whichever occurs first. CEIN Chip enable input CEIN is the input to the chip-enable gating circuit. BC Backup battery input BC should be connected to a 3V backup cell. A voltage within the VBC range on the BC pin should be present upon power up to provide proper oscillator start-up. VOUT Output supply voltage VOUT provides the higher of VCC or VBC, switched internally, to supply external RAM. WE Write enable WE provides the write control for the RTC memory locations. VCC Input supply voltage +5V input 3 Aug. 1995 bq4845/bq4845Y |
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