bq3285LF

Features:

ACPI-compliant day-of-month alarm
Y2K century bit
Direct clock/calendar replace-ment for IBM AT-compatible computers and other applications
2 index shadow registers
2.75.5V operation
240 bytes of general nonvolatile storage
Dedicated 32.768kHz output pin
System wake-up capability-alarm interrupt output active in battery-backup mode
Less than 0.55A load under battery operation
Selectable Intel or Motorola bus timing 24-pin plastic SSOP

Pinout








Specifications

Symbol	Parameter	Value	Unit	Conditions
VCC	DC voltage applied on VCC relative to VSS	-0.3 to 7.0	V
VT	DC voltage applied on any pin excluding VCC relative to VSS	-0.3 to 7.0	V	VT VCC + 0.3
TOPR	Operatingtemperature	0 to +70	°C	Commercial
TSTG	Storage temperature	-55 to +125	°C
TBIAS	Temperature under bias	-40 to +85	°C
TSOLDER	Soldering temperature	260	°C	For 10 seconds

Description

The CMOS bq3285LF is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and bat-tery operation. The architecture is based on the bq3285 RTC with added features: century bit, low-voltage operation, 32.768kHz output, 126 additional bytes of CMOS, two shadow registers of last address used, and a day-of-month alarm to be compliant withtheACPIRTCspecification.


A 32.768kHz output is available for sustaining power-management activities. The bq3285LF 32kHz out-put is always on whenever V_CC is valid. In VCC standby mode, the 32kHz is active, and the bq3285LF typically draws 100A. Wake-up capability is provided by an alarm interrupt, which is ctive in battery-backup mode. In battery-backup mode, current drain is less than 550nA.


The bq3285LF write-protects the clock, calendar, and storage registers during power failure. A backup battery then maintains data and oper-atestheclockandcalendar.


The bq3285LF is a fully compatible real-time clock for IBM AT-compatible computers and other applications. The only external components are a 32.768kHz crystal and a backupbattery.


The bq3285LF is intended for use in 3V systems; however, it may also operate at 5V and then go into a 3V power-down state, write-protecting asifina3Vsystem.

The BQ3285LF is a type of low-power microprocessor peripheral offering a time-of-day clock and 100-year calendar having alarm features and battery operation. The architecture is based on the bq3285 RTC with added features: century bit, low-voltage operation, 32.768kHz output, 126 additional bytes of CMOS, two shadow registers of last address used, and a day-of-month alarm to be compliant with the ACPI RTC specification. A 32.768kHz output is available to keep power-management activities.The bq3285LF 32kHz output is always on whenever VCC is valid. In VCC standby mode, the 32kHz is active, and the bq3285LF typically draws 100A. Wake-up capability is offered by an alarm interrupt.The alarm interrupt is active in batterybackup mode. In battery-backup mode, current drain is less than 550 nA.

The BQ3285LF has the following features:(1)ACPI-compliant day-of-month alarm;(2)Y2K century bit;(3) direct clock/calendar replacement for IBM AT-compatible computers and other applications;(4)2 index shadow registers;(5)2.75.5V operation;(6)240 bytes of general nonvolatile storage(7)dedicated 32.768kHz output pin;(8)system wake-up capability-alarm interrupt output active in battery-backup mode.

The BQ3285LF also has some maximum ratings and crystal characters.maximum ratings:(1):DC voltage applied on VCC relative to VSS is -0.3 V to 7.0 V(2):DC voltage applied on any pin excluding VCC relative to VSS is -0.3 V to 7.0 V (VTVCC + 0.3);(3):operating temperature 0 °C to +70 °C (Commercial);(4):storage temperature is from -55 °Cto +125 °C;(5):temperature under bias is from -40 °Cto +85 °C;(6):soldering temperature is 260 °C For 10 seconds.crystal characters:(1):oscillation frequency is 32.768 kHz typ;(2):load capacitance is 6 pF typ;(3):temperature turnover point is 20°C min, 25°C typ and 30 °C max;(4):parabolic curvature constant is 0.042 ppm/°C max;(5):quality factor is 40000 min and 70,000 max;(6):series resistance is 45 K max;(7):shunt capacitance is 1.1 pF typ and 1.8 pF max;(8)capacitance ratio is 430 typ and 600 max.