Texas Instruments BQ3287MT-SB2, BQ3287MT-I, BQ3287AMT-SB2, BQ3287AMT-I Datasheet

Features

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

Functionally compatible with the DS1287/DS1287A and MC146818A

114 bytes of general nonvolatile storage

Integral lithium cell and crystal

160 ns cycle time allows fast bus operation

Selectable Intel or Motorola bus timing

14 bytes for clock/calendar and control

BCD or binary format for clock and calendar data

Time of day in seconds, minutes, and hours

-12or 24-hour format

-Optional daylight saving adjustment

bq3287/bq3287A

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 122 μs to 500 ms

-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 bq3287/bq3287A 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 114 bytes of general nonvolatile storage. The

bq3287A version is identical to the bq3287, with the addition of the RAM clear input.

The bq3287 is a fully compatible real-time clock for IBM ATcompatible computers and other applications. The bq3287 writeprotects 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 bq3287 is functionally equivalent to the bq3285, except that the battery (16, 20) and crystal (2, 3) pins 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 bq3285 data sheet.

Pin Connections

Pin Names

AD0–AD 7

Multiplexed address/data

RST

Reset input

input/output

MOT

1

24

VCC

MOT

Bus type select input

SQW

Square wave output

NC

2

23

SQW

NC

3

22

NC

NC

No connect

CS

Chip select input

AD0

4

21

NC/RCL

AD1

5

20

NC

RAM clear input

AS

Address strobe input

RCL

AD2

6

19

INT

(bq3287A only)

AD3

7

18

RST

DS

Data strobe input

AD4

8

17

DS

VCC

+5V supply

AD5

9

16

NC

R/W

Read/write input

AD6

10

15

R/W

VSS

Ground

AD7

11

14

AS

INT

Interrupt request output

12

VSS

13

CS

24-Pin DIP Module

PN328701.eps

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bq3287/bq3287A

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
			-20 to +70	°C	Extended “I”
	TSTG	Storage temperature	-40 to +70	°C	Commercial
			-40 to +70	°C	Extended “I”
	TBIAS	Temperature under bias	-10 to +70	°C	Commercial
			-20 to +70	°C	Extended “I”
	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 SQW
	ILO	Output leakage current			-	-	± 1	μA		INT
									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
	ICC	Operating supply current			-	7	15	mA	Min. cycle, duty = 100%,
									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
									(bq3287A only)
	IMOTH	Input current when MOT =			-	-	-185	μA	Internal 30K pull-down
		VCC
	Note:	Typical values indicate operation at TA = 25°C, VCC = 5V.

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