Texas Instruments BQ3287EMT, BQ3287EAMT Datasheet

Features

Direct clock/calendar replacement for IBM®AT-compatible computers and other applications

Functionally compatible with t h e D S 1 2 8 7 / D S 1 2 8 7 A a n d MC146818A/ MC146818B

242 bytes of general nonvolatile storage

Provides a 32.768kHz output for power management

System wake-up capability—

alarm interrupt active in battery-backup mode

Integral lithium cell and crystal

160 ns cycle time allows fast bus operation

14 bytes for clock/calendar and control

Time of day in seconds, minutes, and hours

-12or 24-hour format

-Optional daylight saving adjustment

Pin Connections

MOT	1	24	VCC
NC	2	23	SQW
NC	3	22	EXTRAM
	4
AD0		21	NC/RCL
AD1	5	20	NC
AD2	6	19	INT
AD3	7	18	RST
AD4	8	17	DS
AD5	9	16	NC
AD6	10	15
			R/W
AD7	11	14	AS
VSS	12	13	CS

24-Pin DIP Module

PN3287E1.eps

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bq3287E/bq3287EA

Real-Time Clock (RTC) Module

Calendar in day of the week, day of the month, months, and years with automatic leap-year adjustment

Programmable square wave output

Three individually maskable interrupt event flags:

-Periodic rates from 122μs to

500ms

-Time-of-day alarm once per second to once per day

-End-of-clock update cycle

Better than one minute per month clock accuracy

General Description

The CMOS bq3287E/bq3287EA is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. Other features include three maskable interrupt sources, squarewave output, and 242 bytes of general nonvolatile storage. A 32.768kHz output is available for sustaining power-management activities. Wake-up capability is pro-

vided by an alarm interrupt, which is active in battery-backup mode. The bq3287EA version is identical to the bq3287E, with the addition of the RAM clear input.

The bq3287E is a fully compatible real-time clock for IBM AT-compatible computers and other applications. The bq3287E write-protects the clock, calendar, and storage registers during power failure. The integral backup energy source then maintains data and operates the clock and calendar.

As shipped from Benchmarq, the real time clock is turned off to maximize battery capacity for in-system operation.

The bq3287E is functionally equivalent to the bq3285E, except the battery (16,20) and crystal pins (2,3) are not accessible. These pins are connected internally to a coin cell and quartz crystal. The coin cell is sized to provide 10 years of data retention and clock operation in the absence of power. For a complete description of features, operating conditions, electrical characteristics, bus timing, and pin descriptions, see the bq3285E data sheet.

Pin Names

	AD0–AD7					Multiplex address/data
							RST			Reset input
						input/output
	MOT						SQW			Square wave output
							EXTRAM			Extended RAM enable
	CS					Chip select input
	AS						NC			No connect
						Address strobe input
										RAM clear input
	DS						RCL
						Data strobe input				(bq3287EA only)
						Read/write input
	R/W									+5V supply
							VCC
						Interrupt request output
	INT									Ground
							VSS

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bq3287E/bq3287EA

Absolute Maximum Ratings

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	-0.3 to 7.0	V	VT ≤ VCC + 0.3
	relative to VSS
TOPR	Operating temperature	0 to +70	°C	Commercial
TSTG	Storage temperature	-40 to +70	°C	Commercial
TBIAS	Temperature under bias	-10 to +70	°C	Commercial
TSOLDER	Soldering temperature	260	°C	For 10 seconds

Note: Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability.

Recommended DC Operating Conditions (TA = TOPR)

Symbol	Parameter	Minimum	Typical	Maximum	Unit
VCC	Supply voltage	4.5	5.0	5.5	V
VSS	Supply voltage	0	0	0	V
VIL	Input low voltage	-0.3	-	0.8	V
VIH	Input high voltage	2.2	-	VCC + 0.3	V

Note: Typical values indicate operation at TA = 25°C.

DC Electrical Characteristics (TA = TOPR, VCC = 5V ± 10%)

Symbol		Parameter			Minimum	Typical	Maximum	Unit	Conditions/Notes
ILI		Input leakage current			-	-	± 1	μA	VIN = VSS to VCC
									AD0–AD7,		and
ILO		Output leakage current			-	-	± 1	μA		INT
									SQW in high impedance
VOH		Output high voltage			2.4	-	-	V	IOH = -1.0 mA
VOL		Output low voltage			-	-	0.4	V	IOL = 4.0 mA
									Min. cycle, duty = 100%,
ICC		Operating supply current			-	7	15	mA	IOH = 0mA, IOL = 0mA
VSO		Supply switch-over voltage			-	3.0	-	V
VPFD		Power-fail-detect voltage			4.0	4.17	4.35	V
IRCL		Input current when		= VSS	-	-	185	μA	Internal 30K pull-up
			RCL
									(bq3287EA only)
IMOTH		Input current when MOT =			-	-	-185	μA	Internal 30K pull-down
		VCC
IXTRAM		Input current when			-	-	-185	μA	Internal 30K pull-down
		EXTRAM = VCC
Note:	Typical values indicate operation at TA = 25°C, VCC = 5V.

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