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

Features

➤ Direct clock/calendar replace-

ment 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

-

12- or 24-hour format

- Optional daylight saving

adjustment

➤ 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
500 ms

-

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 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 clockandcalendar.

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.

1

Pin Names

AD0–AD7Multiplexed address/data

input/output

MOT Bus type select input

CS Chip select input

AS Address strobe input

DS Data strobe input

R/W Read/write input

INT Interrupt request output

1

PN328701.eps

24-Pin DIP Module

2
3

4
5
6
7
8

24
23

22
21
20
19
18

17
9
10

16

15
11
12

14

13

V

CC
SQW
NC

NC
INT
RST
DS
NC
R/W
AS
CS

MOT

NC
NC

AD

0

AD

1

AD

2

AD

3

AD

4

AD

5

AD

6

AD

7

V

SS

NC/RCL

Sept. 1996D

RST Reset input

SQW Square wave output

NC No connect

RCL RAM clear input

(bq3287A only)

V

CC

+5V supply

V

SS

Ground

Pin Connections

bq3287/bq3287A

Real-Time Clock(RTC)Module

2

Sept. 1996D

Recommended DC Operating Conditions (T

A=TOPR

)

Symbol Parameter Minimum Typical Maximum Unit

V

CC

Supply voltage 4.5 5.0 5.5 V

V

SS

Supply voltage 0 0 0 V

V

IL

Input low voltage -0.3 - 0.8 V

V

IH

Input high voltage 2.2 - VCC+ 0.3 V

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

Absolute Maximum Ratings

Symbol Parameter Value Unit Conditions

V

CC

DC voltage applied on VCCrelative to V

SS

-0.3 to 7.0 V

V

T

DC voltage applied on any pin excluding V

CC

relative to V

SS

-0.3 to 7.0

VV

T

≤

V

CC

+ 0.3

T

OPR

Operating temperature

0 to +70 °C Commercial

-20 to +70 °C Extended “I”

T

STG

Storage temperature

-40 to +70 °C Commercial

-40 to +70 °C Extended “I”

T

BIAS

Temperature under bias

-10 to +70 °C Commercial

-20 to +70 °C Extended “I”

T

SOLDER

Soldering temperature 260 °C For 10 seconds

Note: Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional opera-

tion 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.

DC Electrical Characteristics (T

A=TOPR,VCC

=5V±10%)

Symbol Parameter Minimum Typical Maximum Unit Conditions/Notes

I

LI

Input leakage current - -

±

1

µ

AVIN=VSSto V

CC

I

LO

Output leakage current - -

±

1

µ

A

AD0–AD7, INT and SQW
in high impedance

V

OH

Output high voltage 2.4 - - V IOH= -1.0 mA

V

OL

Output low voltage - - 0.4 V IOL= 4.0 mA

I

CC

Operating supply current - 7 15 mA

Min. cycle, duty = 100%,
IOH= 0mA, IOL= 0mA

V

SO

Supply switch-over voltage - 3.0 - V

V

PFD

Power-fail-detectvoltage 4.0 4.17 4.35 V

I

RCL

Input current when RCL =V

SS

- - 185

µ

A

Internal 30K pull-up
(bq3287A only)

I

MOTH

Input current when MOT =
V

CC

- - -185

µ

A Internal 30K pull-down

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

bq3287/bq3287A

3

Sept. 1996D

Power-Down/Power-Up Timing (T

A=TOPR)

Symbol Parameter Minimum Typical Maximum Unit Conditions

t

F

VCCslew from 4.5V to 0V 300 - -

µ

s

t

R

VCCslew from 0V to 4.5V 100 - -

µ

s

t

CSR

CS at VIHafter power-up 20 - 200 ms

Internal write-protection
period after VCCpasses V

PFD

on power-up.

t

DR

Data-retention and time­keeping time

10 - - years TA= 25°C.

Note: Clock accuracy is better than±1 minute per month at 25°C for the period of tDR.
Caution: Negative undershoots below the absolute maximum rating of -0.3V in battery-backup mode

may affect data integrity.

Power-Down/Power-Up Timing

bq3287/bq3287A

4

bq3287/bq3287A

Sept. 1996D

24-Pin MT (T-type module)

24-Pin MT (T-type module)

Dimension Minimum Maximum

A 0.360 0.375

A1 0.015 -

B 0.015 0.022
C 0.008 0.013
D 1.320 1.335
E 0.685 0.700

e 0.590 0.620
G 0.090 0.110
L 0.120 0.130
S 0.100 0.120

All dimensions are in inches.

5

Sept. 1996D

bq3287/bq3287A

Ordering Information

Data Sheet Revision History

Change No. Page No. Description Nature of Change

1 1 Address strobe input Clarification
1 2 Power-fail detect voltage V

PFD

Was4.1 min, 4.25 max;
is 4.0 min, 4.35 max

21

Was : “As shipped from Benchmarq,thebackup cell
is electrically isolated from the memory.”
Is: “As shipped from Benchmarq, the backup cell is
electrically isolated from the active circuitry .”

Clarification

22,4

Changed temperature from N (industrial, -40 to
+85°C) to I (extended, -20 to +70°C)

Specification change

32

I

RCL

max. was 275; is now 185. Pull-up = 30K

I

MOTH

max. was -275; is now -185. Pull-down = 30K

Changed values

Notes: Change 1 = Nov. 1992 B changes from June 1991 A.

Change 2 = Nov. 1995 C changes from Nov.1992 B.
Change 3 = Sept. 1996 D changes from Nov.1995 C.

*Contact factory for availability.

bq3287 MT -

PackageOption:

MT = T-type module

Device:

bq3287 Real-Time Clock Module

RAM Clear Option:

A = RAM clear on pin 21
no mark = No connect on pin 21

Temperature:

blank = Commercial (0 to +70°C)
I = Extended* (-20 to +70°C)

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