bq3287/bq3287A
Real-Time Clock (RTC) Module
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
®
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:
bq3287A version is identical to the
bq3287, with the addition of the RAM
clear input.
The bq3287 is a fully compatible
r e a l - t i m e c l o c k f o r I B M AT-
compatible computers and other ap-
p l i c a t i o n s. T h e b q 3 2 8 7 w r i t e -
protects the clock, calendar, and
storage registers during power fail-
ure. The integral backup energy
source then maintains data and op-
erates 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 bq3287 is functionally equiva-
lent 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 de-
scription of features, operating con-
ditions, electrical characteristics,
bus timing, and pin descriptions, see
the bq3285 data sheet.
-
-
-
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 periph-
eral providing a time-of-day clock
and 100-year calendar with alarm
features and battery operation.
Ot he r fe ature s i ncl ude t hree
maskable interrupt sources, square-
wave output, and 114 bytes of gen-
e ral no n volatile storage. The
-
-
12- or 24-hour format
Optional daylight saving
adjustment
Pin Connections
MOT
NC
NC
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
VSS
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
VCC
SQW
NC
NC/RCL
NC
INT
RST
DS
NC
R/W
AS
CS
Pin Names
AD
0
–AD
7
Multiplexed address/data
input/output
Bus type select input
Chip select input
Address strobe input
Data strobe input
Read/write input
Interrupt request output
RST
SQW
NC
RCL
Reset input
Square wave output
No connect
RAM clear input
(bq3287A only)
+5V supply
Ground
MOT
CS
AS
DS
R/W
INT
V
CC
V
SS
24-Pin DIP Module
PN328701.eps
Sept. 1996 D
1
bq3287/bq3287A
Absolute Maximum Ratings
Symbol
V
CC
V
T
T
OPR
T
STG
T
BIAS
T
SOLDER
Note:
Parameter
DC voltage applied on V
CC
relative to V
SS
DC voltage applied on any pin excluding V
CC
relative to V
SS
Operating temperature
Storage temperature
Temperature under bias
Soldering temperature
Value
-0.3 to 7.0
-0.3 to 7.0
0 to +70
-20 to +70
-40 to +70
-40 to +70
-10 to +70
-20 to +70
260
Unit
V
V
°C
°C
°C
°C
°C
°C
°C
V
T
≤
V
CC
+ 0.3
Commercial
Extended “I”
Commercial
Extended “I”
Commercial
Extended “I”
For 10 seconds
Conditions
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. Expo-
sure to conditions beyond the operational limits for extended periods of time may affect device reliability.
Recommended DC Operating Conditions
(TA = TOPR)
Symbol
V
CC
V
SS
V
IL
V
IH
Note:
Parameter
Supply voltage
Supply voltage
Input low voltage
Input high voltage
Typical values indicate operation at T
A
= 25°C.
Minimum
4.5
0
-0.3
2.2
Typical
5.0
0
-
-
Maximum
5.5
0
0.8
V
CC
+ 0.3
Unit
V
V
V
V
DC Electrical Characteristics
(TA = TOPR, VCC = 5V
±
10%)
Symbol
I
LI
I
LO
V
OH
V
OL
I
CC
V
SO
V
PFD
I
RCL
I
MOTH
Note:
Parameter
Input leakage current
Output leakage current
Output high voltage
Output low voltage
Operating supply current
Supply switch-over voltage
Power-fail-detect voltage
Input current when RCL = V
SS
Input current when MOT =
V
CC
Minimum
-
-
2.4
-
-
-
4.0
-
-
Typical
-
-
-
-
7
3.0
4.17
-
-
Maximum
±
1
±
1
-
0.4
15
-
4.35
185
-185
Unit
µA
µA
V
V
mA
V
V
µA
µA
Internal 30K pull-up
(bq3287A only)
Internal 30K pull-down
Conditions/Notes
V
IN
= V
SS
to V
CC
AD
0
–AD
7
, INT and SQW
in high impedance
I
OH
= -1.0 mA
I
OL
= 4.0 mA
Min. cycle, duty = 100%,
I
OH
= 0mA, I
OL
= 0mA
Typical values indicate operation at T
A
= 25°C, V
CC
= 5V.
Sept. 1996 D
2
bq3287/bq3287A
Data Sheet Revision History
Change No.
1
1
Page No.
1
2
Description
Address strobe input
Power-fail detect voltage V
PFD
Was : “As shipped from Benchmarq, the backup cell
is electrically isolated from the memory. ”
Is: “As shipped from Benchmarq, the backup cell is
electrically isolated from the active circuitry. ”
Changed temperature from N (industrial, -40 to
+85°C) to I (extended, -20 to +70°C)
Nature of Change
Clarification
Was 4.1 min, 4.25 max;
is 4.0 min, 4.35 max
2
1
Clarification
2
3
Notes:
2, 4
2
Specification change
I
RCL
max. was 275; is now 185. Pull-up = 30K
I
MOTH
max. was -275; is now -185. Pull-down = 30K Changed values
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.
Ordering Information
bq3287
MT -
Temperature:
blank = Commercial (0 to +70°C)
I = Extended* (-20 to +70°C)
Package Option:
MT = T-type module
RAM Clear Option:
A = RAM clear on pin 21
no mark = No connect on pin 21
Device:
bq3287 Real-Time Clock Module
*Contact factory for availability.
Sept. 1996 D
5
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