Features
Direct clock/calendar replace-
ment 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--
a l a r m
i n t e r r u p t
a c t i v e
i n
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
-
Optional daylight saving
adjustment
Calendar in day of the week, day
of the month, months, and years
with automatic leap-year adjust-
ment
Programmable square wave out-
put
Three individually maskable in-
terrupt event flags:
-
Periodic rates from 122
s 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 periph-
eral providing a time-of-day clock
and 100-year calendar with alarm
features and battery operation.
O t h e r f e a t u r e s i n cl u d e t h r e e
maskable interrupt sources, square-
wave output, and 242 bytes of gen-
e r a l
n o n v o l a t i l e
s t o r a g e.
A
32.768kHz output is available for
sustaining power-management ac-
tivities. 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, cal-
endar, and storage registers during
power failure. The integral backup en-
ergy source then maintains data and
operates the clock and calendar.
As shipped from Benchmarq, the
real time clock is turned off to maxi-
mize battery capacity for in-system
operation.
The bq3287E is functionally equiva-
lent to the bq3285E, except the bat-
tery (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 re-
tention and clock operation in the
absence of power. For a complete de-
scription of features, operating con-
ditions, electrical characteristics,
bus timing, and pin descriptions, see
the bq3285E data sheet.
1
Real-Time Clock (RTC) Module
bq3287E/bq3287EA
Sept. 1996 C
Pin Names
AD0AD7 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
1
PN3287E1.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
VCC
SQW
EXTRAM
NC
INT
RST
DS
NC
R/W
AS
CS
MOT
NC
NC
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
VSS
NC/RCL
RST
Reset input
SQW
Square wave output
EXTRAM
Extended RAM enable
NC
No connect
RCL
RAM clear input
(bq3287EA only)
V
CC
+5V supply
V
SS
Ground
Pin Connections
2
Recommended DC Operating Conditions
(TA = 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
-
V
CC
+ 0.3
V
Note:
Typical values indicate operation at T
A
= 25C.
Absolute Maximum Ratings
Symbol
Parameter
Value
Unit
Conditions
V
CC
DC voltage applied on V
CC
relative 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
V
V
T
V
CC
+ 0.3
T
OPR
Operating temperature
0 to +70
C
Commercial
T
STG
Storage temperature
-40 to +70
C
Commercial
T
BIAS
Temperature under bias
-10 to +70
C
Commercial
T
SOLDER
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.
Sept. 1996 C
DC Electrical Characteristics
(TA = TOPR, VCC = 5V
10%)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
Conditions/Notes
I
LI
Input leakage current
-
-
1
A
V
IN
= V
SS
to V
CC
I
LO
Output leakage current
-
-
1
A
AD
0
AD
7
, INT and
SQW in high impedance
V
OH
Output high voltage
2.4
-
-
V
I
OH
= -1.0 mA
V
OL
Output low voltage
-
-
0.4
V
I
OL
= 4.0 mA
I
CC
Operating supply current
-
7
15
mA
Min. cycle, duty = 100%,
I
OH
= 0mA, I
OL
= 0mA
V
SO
Supply switch-over voltage
-
3.0
-
V
V
PFD
Power-fail-detect voltage
4.0
4.17
4.35
V
I
RCL
Input current when RCL = V
SS
-
-
185
A
Internal 30K pull-up
(bq3287EA only)
I
MOTH
Input current when MOT =
V
CC
-
-
-185
A
Internal 30K pull-down
I
XTRAM
Input current when
EXTRAM = V
CC
-
-
-185
A
Internal 30K pull-down
Note:
Typical values indicate operation at T
A
= 25C, V
CC
= 5V.
bq3287E/bq3287EA
3
Sept. 1996 C
Power-Down/Power-Up Timing
(TA = TOPR)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
Conditions
t
F
V
CC
slew from 4.5V to 0V
300
-
-
s
t
R
V
CC
slew from 0V to 4.5V
100
-
-
s
t
CSR
CS at V
IH
after power-up
20
-
200
ms
Internal write-protection
period after V
CC
passes V
PFD
on power-up.
t
DR
Data-retention and time-
keeping time
10
-
-
years
T
A
= 25C.
Note:
Clock accuracy is better than
1 minute per month at 25C for the period of t
DR
.
Caution:
Negative undershoots below the absolute maximum rating of -0.3V in battery-backup mode
may affect data integrity.
Power-Down/Power-Up Timing
bq3287E/bq3287EA
5
Sept. 1996 C
bq3287E/bq3287EA
Ordering Information
Data Sheet Revision History
Change No.
Page No.
Description
Nature of Change
1
8
Register C, bit 2
Was 0; is na (not affected)
2
2
I
RCL
max. was 275; is now 185. Pull-down = 30K. Value change
2
2
I
XTRAM
max. was -75; is now -185.
Value change
Notes:
Change 1 = Apr. 1994 B "Final" changes from Dec. 1993 A "Preliminary."
Change 2 = Sept. 1996 C changes from April 1994 B.
Temperature:
blank = Commercial (0 to +70C)
bq3287E
MT -
Package Option:
MT = T-type module
Device:
bq3287E Real-Time Clock Module
RAM Clear Option:
A = RAM clear on pin 21
no mark = No connect on pin 21
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