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Электронный компонент: BQ4287

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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
Automatic backup supply and
write-protection to make external
SRAM nonvolatile
Integral lithium cell and crystal
160 ns cycle time allows fast bus
operation
Intel bus timing
14 bytes for clock/calendar and
control
BCD or binary format for clock
and calendar data
Calendar in day of the week, day of
the month, months, and years with
automatic leap-year adjustment
Time of day in seconds, minutes,
and hours
-
12- or 24-hour format
-
Optional daylight saving
adjustment
Programmable square wave out-
put
Three individually maskable in-
terrupt event flags:
-
Periodic rates from 122
s 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 bq4287 is a low-power
microprocessor peripheral providing
a time-of-day clock and 100-year cal-
endar with alarm features and bat-
tery operation. Other features in-
clude three maskable interrupt
sources, square wave output, and
114 bytes of general nonvolatile
storage.
The bq4287 write-protects the clock,
calendar, and storage registers dur-
ing power failure. The integral
backup energy source then main-
tains data and operates the clock
and calendar.
The bq4287 uses its integral battery-
backup controller and battery to make
a standard CMOS SRAM nonvolatile
during power-fail conditions. During
power-fail, the bq4287 automatically
write-protects the external SRAM and
provides a V
CC
output sourced from its
internal battery.
The bq4287 is a fully compatible
real-time clock for IBM AT-compatible
computers and other applications.
As shipped from Benchmarq, the
backup cell is electrically isolated
from the memory. Following the first
application of V
CC
, this isolation is
broken, and the backup cell provides
data retention to the clock, internal
RAM, V
OUT
, and CE
OUT
on subse-
quent power-downs.
The bq4287 is functionally equiva-
lent to the bq4285, except that 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 pro-
vides 130mAh of capacity. For a
complete description of features, op-
erating conditions, electrical charac-
teristics, bus timing, and pin de-
scriptions, see the bq4285 data
sheet.
1
Pin Names
AD
0
AD
7
Multiplexed address/data
input/output
CS
Chip select input
ALE
Address strobe input
RD
Data strobe input
WR
Read/write input
INT
Interrupt request output
RST
Reset input
SQW
Square wave output
CE
IN
RAM chip enable input
CE
OUT
RAM chip enable output
NC
No connect
V
OUT
Supply output
V
CC
+5V supply
V
SS
Ground
1
PN428701.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
CEOUT
NC
INT
RST
RD
NC
WR
ALE
CS
VOUT
NC
NC
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
VSS
CEIN
bq4287
Pin Connections
Real-Time Clock Module With NVRAM Control
Caution:
Take care to avoid inadvertent dis-
charge through V
OUT
and
CE
OUT
after battery isolation has been
broken.
Nov. 1993 C
2
Nov. 1993 C
Recommended DC Operating Conditions
(T
A
= T
OPR
)
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.
DC Electrical Characteristics
(T
A
= T
OPR
, V
CC
= 5V
10%)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
Conditions/Notes
C
Battery capacity
-
130
-
mAh
Refer to graphs in Typical Bat-
tery Characteristics section
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
I
CCB
Battery operation current
-
0.3
0.5
A
V
BC
= 3V, T
A
= 25C, no load
on V
OUT
or CE
OUT
V
SO
Supply switch-over voltage
-
3.0
-
V
V
PFD
Power-fail-detect voltage
4.0
4.17
4.35
V
V
BC
Backup cell voltage
-
3.0
-
V
Internal backup cell voltage;
refer to graphs in Typical Bat-
tery Characteristics section
V
OUT1
V
OUT
voltage
V
CC
- 0.3V
-
-
V
I
OUT
= 100mA, V
CC
> V
BC
V
OUT2
V
OUT
voltage
V
BC
- 0.3V
-
-
V
I
OUT
= 100
A, V
CC
< V
BC
I
CE
Chip enable input current
-
-
100
A
Internal 50K pull-up
Note:
Typical values indicate operation at T
A
= 25C, V
CC
= 5V.
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 con-
ditions beyond the operational limits for extended periods of time may affect device reliability.
bq4287
3
Nov. 1993 C
Power-Down/Power-Up Timing
(T
A
= T
OPR)
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, no load on V
OUT
or
CE
OUT
.
t
WPT
Write-protect time for
external RAM
10
16
30
s
Delay after V
CC
slows down
past V
PFD
before SRAM is
write-protected.
t
CER
Chip enable recovery time
t
CSR
-
t
CSR
ms
Time during which external
SRAM is write-protected after
V
CC
passes V
PFD
on power-up.
t
CED
Chip enable propagation
delay to external SRAM
-
7
10
ns
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
bq4287
4
Nov. 1993 C
Typical Battery Characteristics
(source = Panasonic)
1.50
2.00
2.50
3.00
3.50
0
1000
2000
3000
4000
5000
Voltage
(V)
Duration (hours)
15K
(190 A)
30K
(95 A)
100K
(29 A)
Temp: 20C (68F)
CR1632 Load Characteristics
Capacity
(mAh)
0
25
50
75
100
125
150
1
10
100
60C (140F)
20C (68F)
Load (K )
|
2000
|
1000
|
500
|
300
|
200
|
100
|
50
|
30
Cut off V: 2.0V
( A)
CR1632 Capacity vs. Load Resistance
bq4287
5
Nov. 1993 C
1.50
2.00
2.50
3.00
3.50
0
100
200
300
400
500
600
700
800
Voltage
(V)
Duration (hours)
-10C (14F)
Load: 15K (190 A)
20C (68F)
60C (140F)
CR1632 Temperature Characteristics
Voltage
(V)
2.20
2.40
2.60
2.80
3.00
3.20
1
10
100
20C (68F)
Load (K )
|
2000
|
1000
|
500
|
300
|
200
|
100
|
50
|
30
(uA)
-10C (14F)
60C (140F)
Voltage at 50% discharge
CR1632 Operating Voltage vs. Load Resistance
bq4287