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參數資料
| 型號： | BQ4845S |
| 英文描述： | Fast Recovery Glass Passivated Rectifier Diodes |
| 中文描述： | 實時時鐘 |
| 文件頁數： | 1/20頁 |
| 文件大小： | 1155K |
| 代理商： | BQ4845S |
Features
Real-Time Clock counts seconds
through years in BCD format
On-chip battery-backup switchover
circuit with nonvolatile control for
external SRAM
Less than 500nA of clock opera-
tion current in backup mode
Microprocessor reset valid to
V
CC
= V
SS
Independent watchdog timer
with a programmable time-out
period
Power-fail interrupt warning
Programmable clock alarm inter-
rupt active in battery-backup
mode
Programmableperiodic interrupt
Battery-low warning
General Description
The bq4845 Real-Time Clock is a
low-power microprocessor periph-
eral that integrates a time-of-day
clock, a 100-year calendar, and a
CPU supervisor in a 28-pin SOIC or
DIP. The bq4845 is ideal for fax ma-
chines, copiers, industrial control
systems, point-of-sale terminals,
data loggers, and computers.
The bq4845 provides direct connec-
tions for a 32.768KHz quartz crystal
and a 3V backup battery. Through
the use of the conditional chip en-
able output (CE
OUT
) and battery
voltage output (V
OU T
) pins, the
bq4845 can write-protect and make
nonvolatile external SRAMs. The
backup cell powers the real-time
clock and maintains SRAM infor-
mation in the absence of system
voltage.
The bq4845 contains a temperature-
compensated reference and comparator
circuit that monitors the status of its
voltage supply. When the bq4845 de-
tects an out-of-tolerance condition, it
generates an interrupt warning and
subsequently a microprocessor reset.
The reset stays active for 200ms after
V
CC
rises within tolerance, to allow for
power supply and processor stabiliza-
tion.
T he bq4845 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 pe-
riod, the bq4845 asserts WDO and
RST. WDI unconnected disables the
watchdog timer.
The bq4845 can generate other in-
terrupts based on a clock alarm con-
dition 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 inter-
rupts at a rate beyond once per sec-
ond, the periodic interrupt can be pro-
grammed with periods of 30.5
μ
s to
500ms.
1
Aug. 1995
1
2
3
4
5
6
7
8
9
10
11
12
13
14
PN484501.eps
28-DIP or SOIC
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
CC
WE
CE
IN
CE
OUT
BC
WDI
OE
CS
V
SS
DQ
7
DQ
8
DQ
5
DQ
4
DQ
3
V
OUT
X
1
X
2
WDO
INT
RST
A
3
A
2
A
1
A
0
DQ
0
DQ
1
DQ
2
V
SS
Pin Connections
A
0
–A
3
Clock/control address
inputs
DQ
0
–DQ
7
Data inputs/outputs
WE
Write enable
OE
Output enable
CS
Chip select input
CE
IN
External RAM chip
enable
CE
OUT
Conditional RAM chip
enable
X1–X2
Crystal inputs
Pin Names
BC
Backup battery input
V
OUT
Back-up battery output
INT
Interrupt output
RST
Microprocessor reset
WDI
Watchdog input
WDO
Watchdog output
V
CC
+5V supply
V
SS
Ground
bq4845/bq4845Y
Parallel RTC With CPU Supervisor
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相關PDF資料 |
PDF描述 |
|---|---|
| BQ4845YP | Fast Recovery Glass Passivated Rectifier Diodes |
| BQ4845YS | Fast Recovery Glass Passivated Rectifier Diodes |
| BQ4847Y | Fast Recovery Glass Passivated Rectifier Diodes |
| BQ48S1.5-30A | Fast Recovery Glass Passivated Rectifier Diodes |
| BQ48S2-40R | DC to DC Converter |
相關代理商/技術參數 |
參數描述 |
|---|---|
| BQ4845S- | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Parallel RTC With CPU Supervisor |
| BQ4845S-A4 | 功能描述:實時時鐘 w/NVSRAM Control Watchdog Timer RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線接口:I2C 日期格式:DW:DM:M:Y 時間格式:HH:MM:SS RTC 存儲容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube |
| BQ4845S-A4G4 | 功能描述:實時時鐘 w/NVSRAM Control Watchdog Timer RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線接口:I2C 日期格式:DW:DM:M:Y 時間格式:HH:MM:SS RTC 存儲容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube |
| BQ4845S-A4N | 功能描述:實時時鐘 w/NVSRAM Control Watchdog Timer RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線接口:I2C 日期格式:DW:DM:M:Y 時間格式:HH:MM:SS RTC 存儲容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube |
| BQ4845S-A4NG4 | 功能描述:實時時鐘 w/NVSRAM Control Watchdog Timer RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線接口:I2C 日期格式:DW:DM:M:Y 時間格式:HH:MM:SS RTC 存儲容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube |
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