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
bq3287E/bq3287EA
Power-Down/Power-Up Timing (T
Symbol Parameter Minimum Typical Maximum Unit Conditions
t
F
t
R
t
CSR
t
DR
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
VCCslew from 4.5V to 0V 300 - VCCslew from 0V to 4.5V 100 - -
CS at VIHafter power-up 20 - 200 ms
Data-retention and timekeeping time
may affect data integrity.
A=TOPR)
s
µ
s
µ
Internal write-protection
period after VCCpasses V
on power-up.
10 - - years TA= 25°C.
PFD
Power-Down/Power-Up Timing
Sept. 1996C
3
bq3287E/bq3287EA
24-Pin MT (T-type module)
24-Pin MT(T-Type Module
Inches Millimeters
Dimension
A 0.360 0.390 9.14 9.91
A1 0.015 - 0.38 -
B 0.015 0.022 0.38 0.56
C 0.008 0.013 0.20 0.33
D 1.320 1.335 33.53 33.91
E 0.710 0.740 18.03 18.80
e 0.590 0.620 14.99 15.75
G 0.090 0.110 2.29 2.79
L 0.110 0.130 2.79 3.30
S 0.100 0.120 2.54 3.05
Min. Max. Min. Max.
)
Sept. 1996C
4
bq3287E/bq3287EA
Data Sheet Revision History
Change No. Page No. Description Nature of Change
1 8 Register C, bit 2 Was0; is na (not affected)
22I
22I
max. was 275; is now 185. Pull-down = 30K. V aluechange
RCL
max. was -75; is now -185. Value change
XTRAM
Notes: Change 1 = Apr.1994 B “Final” changes from Dec. 1993 A “Preliminary.”
Change 2 = Sept. 1996 C changes from April 1994 B.
Ordering Information
bq3287E MT -
Temperature:
blank = Commercial (0 to +70°C)
PackageOption:
MT = T-type module
RAM Clear Option:
A = RAM clear on pin 21
no mark = No connect on pin 21
Device:
bq3287E Real-Time Clock Module
Sept. 1996C
5
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