TI BQ4847MT

bq4847/bq4847Y
RTC Module With CPU Supervisor
Features
General Description
tolerance to allow for power supply
and processor stabilization.
➤ Real-Time Clock counts seconds
through years in BCD format
The bq4847 Real-Time Clock Module is a low-power microprocessor
peripheral that integrates a timeof-day clock, a 100-year calendar, a
CPU supervisor, a battery, and a crystal in a 28-pin DIP module. The part
is ideal for fax machines, copiers, industrial control systems, point-of-sale
terminals, data loggers, and computers.
The bq4847 also has a built-in
watchdog timer to monitor processor
operation. If the microprocessor does
not toggle the watchdog input (WDI)
within the programmed time-out,
the bq4847 asserts WDO and RST.
WDI unconnected disables the
watchdog timer.
➤ Integrated battery and crystal
➤ On-chip battery-backup switchover circuit with nonvolatile control for an external SRAM
➤ 130mAh battery capacity
➤ ± 1 minute per month clock accuracy
➤ Less than 500nA of clock operation current in backup mode
➤ Microprocessor reset valid to
VCC = VSS
➤ Independent watchdog timer
with a programmable time-out
period
➤ Power-fail interrupt warning
➤ Programmable clock alarm interrupt active in battery-backup
mode
➤ Programmable periodic interrupt
➤ Battery-low warning
Pin Connections
VOUT
NC
NC
WDO
INT
RST
A3
A2
A1
A0
DQ0
DQ1
DQ2
VSS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
The bq4847 contains an internal
battery and crystal. Through the use
of the conditional chip enable output
(CEOUT) and battery voltage output
(VOUT) pins, the bq4847 can writeprotect and make nonvolatile an
external SRAM. The backup cell
powers the real-time clock and
maintains SRAM information in
the absence of system voltage.
The
bq4847
contains
a
temperature-compensated reference and comparator circuit that
monitors the status of its voltage
supply. When an out-of-tolerance
condition is detected, the bq4847
generates an interrupt warning
and subsequently a microprocessor reset. The reset stays active
for 200ms after V CC rises within
The bq4847 can generate other interrupts based on a clock alarm condition or a periodic setting. The
alarm interrupt can be set to occur
from once per second to once per
month. The alarm can be made active in the battery-backup mode to
serve as a system wake-up call. For
interrupts at a rate beyond once per
second, the periodic interrupt can be
programmed with periods of 30.5µs
to 500ms.
Caution:
Take care to avoid inadvertent discharge through VOUT and CEOUT
after battery isolation has been
broken.
Pin Names
VCC
WE
CEIN
CEOUT
NC
WDI
OE
CS
NC
DQ7
DQ6
DQ5
DQ4
DQ3
28-Pin DIP Module
PN484701.eps
A0–A3
Clock/Control address
inputs
DQ0–DQ7
Data inputs/outputs
WE
Write enable
OE
Output enable
CS
Chip select input
CEIN
External RAM chip
enable
CEOUT
Conditional RAM chip
enable
Sept. 1996
1
NC
No connect
VOUT
Back-up battery output
INT
Interrupt output
RST
Microprocessor reset
WDI
Watchdog input
WDO
Watchdog output
VCC
+5V supply
VSS
Ground
bq4847/bq4847Y
room temperature. For a complete description of features, operating conditions, electrical characteristics,
bus timing, and pin descriptions, see the bq4845 data
sheet. Valid part types for ordering are bq4847MT (5%)
and bq4847YMT (10%).
Functional Description
Figure 1 is a block diagram of the bq4847. The bq4847 is
functionally equivalent to the bq4845 except that the battery (20, 24) and crystal (2, 3) pins are not accessible. The
pins are connected internally to a coin cell and quartz
crystal. The coin cell provides 130mAh of capacity. It is internally isolated from VOUT and CEOUT until the initial
application of VCC. Once VCC rises above VPFD, this isolation is broken, and the backup cell provides power to
VOUT and CEOUT for the external SRAM. The real-time
clock keeps time to within one minute per month at
Figure 2 illustrates the address map for the bq4847. Table 1 is a map of the bq4847 registers, and Table 2 describes the register bits.
Figure 1. Block Diagram
Truth Table
VCC
CS
OE
WE
CEOUT
VOUT
Mode
DQ
Power
< VCC (max.)
VIH
X
X
CEIN
VOUT1
Deselect
High Z
Standby
VIL
X
VIL
CEIN
VOUT1
Write
DIN
Active
> VCC (min.)
VIL
VIL
VIH
CEIN
VOUT1
Read
DOUT
Active
VIL
VIH
VIH
CEIN
VOUT1
Read
High Z
Active
< VPFD (min.) > VSO
X
X
X
VOH
VOUT1
Deselect
High Z
CMOS standby
≤ VSO
X
X
X
VOHB
VOUT2
Deselect
High Z
Battery-backup mode
Sept. 1996
2
bq4847/bq4847Y
MT: 28-Pin T-Type Module
28-Pin MT (T-Type Module)
Inches
Millimeters
Dimension
Min.
Max.
Min.
Max.
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
1.520
1.535
38.61
38.99
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
Ordering Information
bq4847
- MT
Package Option:
MT = 28-pin T-type Module
Voltage Tolerance:
Blank = 5%
Y = 10%
Device:
bq4847 Real-Time Clock Module With CPU Supervisor
Sept. 1996
3
PACKAGE OPTION ADDENDUM
www.ti.com
9-Oct-2007
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
BQ4847MT
ACTIVE
DIP MOD
ULE
MT
28
1
Pb-Free
(RoHS)
CU SN
N / A for Pkg Type
BQ4847YMT
ACTIVE
DIP MOD
ULE
MT
28
1
Pb-Free
(RoHS)
CU SN
N / A for Pkg Type
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
MECHANICAL DATA
MPDI064 – MAY 2001
MT (R-PDIP-T**)
PLASTIC DUAL-IN-LINE
28 PINS SHOWN
Inches
D
Millimeters
Min.
Dimension
Min.
Max.
A
0.360
0.390
9.14
A1
0.015
0.38
Max.
9.91
–
B
0.015
–
0.022
0.38
0.56
C
0.008
0.013
0.20
0.33
D/24 PIN
1.320
1.335
33.53
33.91
D/28 PIN
1.520
1.535
38.61
38.99
E
0.710
0.740
18.03
18.80
e
G
0.590
0.630
16.00
0.090
0.110
14.99
2.29
L
0.110
2.79
3.30
S
0.100
0.130
0.120
2.54
3.05
2.79
E
A1
A
C
B
L
S
e
G
4201978/A 03/01
NOTES: A. All linear dimensions are in inches (mm).
B. This drawing is subject to change without notice.
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