Texas Instruments BQ3287EMT, BQ3287EAMT Datasheet

Features

➤ Direct clock/calendar replace-

ment for IBM
computers and other applications

➤ Functionally compatible with

the DS1287/DS1287A and
MC146818A/ MC146818B

➤ 242 bytes of general nonvolatile

storage

➤ Provides a 32.768kHz output for

power management

➤ System wake-upcapability—

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

-

12- or 24-hour format

®

AT-compatible

- Optional daylight saving

adjustment

Pin Connections

MOT

1

NC

2

NC

3
4

AD

0

5

AD

1

AD

6

2

AD

7

3

AD

8

4

AD

9

5

AD

10

6

11

AD

7

12

V

SS

24-Pin DIP Module

24
23

22
21
20
19
18
17
16
15
14

13

PN3287E1.eps

V

CC
SQW
EXTRAM
NC/RCL
NC
INT
RST
DS
NC
R/W
AS
CS

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 out-

put

➤ Three individually maskable in-

terrupt event flags:

Periodic rates from 122µsto

-

500ms
Time-of-day alarm once per

-

second to once per day
End-of-clock update cycle

-

➤ Better than one minute per

month clockaccuracy

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-

Pin Names

AD0–AD7 Multiplex address/data

input/output

MOT

CS Chip select input

AS Address strobe input

DS Data strobe input

R/W Read/write input

INT Interrupt request output

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 clockandcalendar .

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.

RST Reset input

SQW Square wave output

EXTRAM Extended RAM enable

NC No connect

RCL RAM clear input

(bq3287EA only)

V

CC

V

SS

+5V supply

Ground

Sept. 1996C

1

bq3287E/bq3287EA

Absolute Maximum Ratings

Symbol Parameter Value Unit Conditions

V

CC

V

T

T

OPR

T

STG

T

BIAS

T

SOLDER

DC voltage applied on VCCrelative to V
DC voltage applied on any pin excluding V

relative to V

SS

SS

CC

Operating temperature 0 to +70 °C Commercial
Storage temperature -40 to +70 °C Commercial
Temperature under bias -10 to +70 °C Commercial
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.

-0.3 to 7.0 V

-0.3 to 7.0

VV

V

≤

T

CC

+ 0.3

Recommended DC Operating Conditions (T

A=TOPR

)

Symbol Parameter Minimum Typical Maximum Unit

V

CC

V

SS

V

IL

V

IH

Supply voltage 4.5 5.0 5.5 V
Supply voltage 0 0 0 V
Input low voltage -0.3 - 0.8 V
Input high voltage 2.2 - VCC+ 0.3 V

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

DC Electrical Characteristics (T

A=TOPR,VCC

=5V±10%)

Symbol Parameter Minimum Typical Maximum Unit Conditions/Notes

I

LI

I

LO

V

OH

V

OL

Input leakage current - ­Output leakage current - -

± 1 µA
± 1 µA

VIN=VSSto V
AD0–AD7, INT and

SQW in high impedance
Output high voltage 2.4 - - V IOH= -1.0 mA
Output low voltage - - 0.4 V IOL= 4.0 mA

Min. cycle, duty = 100%,

I

CC

V

SO

V

PFD

I

RCL

I

MOTH

I

XTRAM

Operating supply current - 7 15 mA
Supply switch-over voltage - 3.0 - V
Power-fail-detectvoltage 4.0 4.17 4.35 V

Input current when RCL =V
Input current when MOT =

V

CC

Input current when
EXTRAM = V

CC

SS

- - 185

- - -185

- - -185

IOH= 0mA, IOL= 0mA

Internal 30K pull-up

µA

(bq3287EA only)

Internal 30K pull-down

µA

Internal 30K pull-down

µA

Note: Typical values indicate operation at TA= 25°C, VCC=5V.

CC

Sept. 1996C

2