BQ4847 [TI]
RTC Module With CPU Supervisor; RTC模块， CPU监控电路
| 型号： | BQ4847 |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | RTC Module With CPU Supervisor |
| 文件： | 总5页 (文件大小：224K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
bq4847/bq4847Y
RTC Module With CPU Supervisor
tolerance to allow for power supply
General Description
Features
and processor stabilization.
➤ Real-Time Clock counts seconds
The bq4847 Real-Time Clock Mod-
Th e bq4847 a ls o h a s a bu ilt -in
ule is a low-power microprocessor
through years in BCD format
watchdog timer to monitor processor
peripheral that integrates a time-
➤ Integrated battery and crystal
operation. If the microprocessor does
of-day clock, a 100-year calendar, a
not toggle the watchdog input (WDI)
CPU supervisor, a battery, and a crys-
➤ On-chip battery-backup switch-
over circuit with nonvolatile con-
trol for an external SRAM
within the programmed time-out,
tal in a 28-pin DIP module. The part
the bq4847 asserts WDO and RST.
is ideal for fax machines, copiers, in-
WD I u n con n e ct e d d is a b le s t h e
dustrial control systems, point-of-sale
watchdog timer.
➤ 130mAh battery capacity
terminals, data loggers, and comput-
ers.
The bq4847 can generate other in-
➤ ±1 minute per month clock accu-
terrupts based on a clock alarm con-
Th e bq4847 con t a in s a n in t er n a l
racy
dition or a periodic setting. The
battery and crystal. Through the use
➤ Less than 500nA of clock opera-
alarm interrupt can be set to occur
of the conditional chip enable output
tion current in backup mode
from once per second to once per
(CEOUT) and battery voltage output
month. The alarm can be made ac-
(VOUT) pin s, t h e bq4847 can write-
➤ Microprocessor reset valid to
tive in the battery-backup mode to
protect and make n on vola t ile a n
VCC = VSS
serve as a system wake-up call. For
ext er n a l SRAM. Th e ba cku p cell
interrupts at a rate beyond once per
p ower s t h e r ea l-t im e clock a n d
➤ I n d ep en d en t wa t ch d og t im er
with a programmable time-out
period
second, the periodic interrupt can be
programmed with periods of 30.5µs
to 500ms.
m a in t a in s SRAM in for m a t ion in
the absence of system voltage.
➤ Power-fail interrupt warning
T h e
b q 4 8 4 7
con t a i n s
a
t em per a t u r e-com pen sa t ed r efer-
ence and comparator circuit that
monitors the status of its voltage
su pply. Wh en a n ou t -of-t oler a n ce
condition is detected, the bq4847
gen er a t es a n in t er r u pt wa r n in g
a n d su bsequ en t ly a m icr opr oces-
sor r eset . Th e r eset st a ys a ct ive
for 200m s a ft er VCC r ises wit h in
➤ Programmable clock alarm inter-
r u pt a ct ive in ba t t er y-ba cku p
mode
Caution:
Take care to avoid inadvertent dis-
charge through VOUT and CEOUT
after battery isolation has been
broken.
➤ Programmable periodic interrupt
➤ Battery-low warning
Pin Connections
Pin Names
A0–A3
Clock/Control address
inputs
NC
No connect
V
28
1
V
OUT
NC
NC
CC
WE
27
26
2
3
VOUT
INT
Back-up battery output
Interrupt output
Microprocessor reset
Watchdog input
Watchdog output
+5V supply
CE
CE
NC
IN
DQ0–DQ7 Data inputs/outputs
4
WDO
INT
25
24
23
22
21
20
19
18
17
16
15
OUT
5
WE
OE
Write enable
RST
6
WDI
OE
CS
RST
WDI
WDO
VCC
VSS
A
3
7
Output enable
Chip select input
A
A
A
8
9
2
1
0
NC
10
11
12
13
14
DQ
7
DQ
DQ
DQ
DQ
CS
DQ
0
1
2
6
DQ
DQ
5
4
3
CEIN
External RAM chip
enable
V
SS
Ground
CEOUT
Conditional RAM chip
enable
28-Pin DIP Module
PN484701.eps
Sept. 1996
1
bq4847/bq4847Y
room temperature. For a complete description of fea-
tures, 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 bat-
tery (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 in-
ternally isolated from VOUT and CEOUT until the initial
application of VCC. Once VCC rises above VPFD, this isola-
tion 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. Ta-
ble 1 is a map of the bq4847 registers, and Table 2 de-
scribes the register bits.
Figure 1. Block Diagram
Truth Table
VCC
CS
VIH
VIL
VIL
VIL
X
OE
X
WE
X
CEOUT
CEIN
CEIN
CEIN
CEIN
VOH
VOUT
VOUT1
VOUT1
VOUT1
VOUT1
VOUT1
VOUT2
Mode
Deselect
Write
DQ
Power
Standby
Active
< VCC (max.)
High Z
DIN
X
VIL
VIH
VIH
X
> VCC (min.)
VIL
VIH
X
Read
DOUT
High Z
High Z
Active
Read
Active
< VPFD (min.) > VSO
Deselect
Deselect
CMOS standby
X
X
X
VOHB
High Z Battery-backup mode
≤ VSO
Sept. 1996
2
bq4847/bq4847Y
MT: 28-Pin T-Type Module
(
)
28-Pin MT T-Type Module
Inches
Millimeters
Dimension
Min.
0.360
0.015
0.015
0.008
1.520
0.710
0.590
0.090
0.110
0.100
Max.
0.390
-
Min.
Max.
9.91
-
A
A1
B
C
D
E
9.14
0.38
0.022
0.013
1.535
0.740
0.620
0.110
0.130
0.120
0.38
0.56
0.33
38.99
18.80
15.75
2.79
3.30
3.05
0.20
38.61
18.03
14.99
2.29
e
G
L
2.79
S
2.54
Ordering Information
bq4847
- MT
Pa ck a ge Op tion :
MT = 28-pin T-type Module
Volta ge Toler a n ce:
Blank = 5%
Y = 10%
Device:
bq4847 Real-Time Clock Module With CPU Supervisor
Sept. 1996
3
PACKAGE OPTION ADDENDUM
www.ti.com
4-Mar-2005
PACKAGING INFORMATION
Orderable Device
Status (1)
Package Package
Type Drawing
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
BQ4847MT
ACTIVE
ACTIVE
0
0
1
1
None
None
Call TI
Call TI
Call TI
Call TI
BQ4847YMT
(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 - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
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.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
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Addendum-Page 1
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