參數(shù)資料
型號(hào)： BQ4845S-A4
廠商： TEXAS INSTRUMENTS INC
元件分類(lèi)： XO, clock
英文描述： 1 TIMER(S), REAL TIME CLOCK, PDSO28
封裝： 0.300 INCH, GREEN, SOIC-28
文件頁(yè)數(shù)： 1/24頁(yè)
文件大?。?/td> 1287K
代理商： BQ4845S-A4
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
VCC =VSS
Independent watchdog timer
with a programmable time-out
period
Power-fail interrupt warning
Programmable clock alarm inter-
rupt active in battery-backup
mode
Programmable periodic 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 (CEOUT) and battery
voltage output (VOUT) 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
VCC rises within tolerance, to allow for
power supply and processor stabiliza-
tion.
The 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
sto
500ms.
1
Aug. 1995
1
PN484501.eps
28-DIP or SOIC
2
3
4
5
6
7
8
28
27
26
25
24
23
22
21
9
10
20
19
11
12
18
17
13
14
VCC
WE
CEIN
CEOUT
BC
WDI
OE
CS
VSS
DQ7
DQ8
DQ5
DQ4
DQ3
16
15
VOUT
X1
X2
WDO
INT
RST
A3
A2
A1
A0
DQ0
DQ1
DQ2
VSS
Pin Connections
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
X1–X2
Crystal inputs
Pin Names
BC
Backup battery input
VOUT
Back-up battery output
INT
Interrupt output
RST
Microprocessor reset
WDI
Watchdog input
WDO
Watchdog output
VCC
+5V supply
VSS
Ground
bq4845/bq4845Y
Parallel RTC With CPU Supervisor
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
BQ4845S-A4G4 功能描述:實(shí)時(shí)時(shí)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(shí)間格式:HH:MM:SS RTC 存儲(chǔ)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(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
BQ4845S-A4N 功能描述:實(shí)時(shí)時(shí)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(shí)間格式:HH:MM:SS RTC 存儲(chǔ)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(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
BQ4845S-A4NG4 功能描述:實(shí)時(shí)時(shí)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(shí)間格式:HH:MM:SS RTC 存儲(chǔ)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(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
BQ4845S-A4NTR 功能描述:實(shí)時(shí)時(shí)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(shí)間格式:HH:MM:SS RTC 存儲(chǔ)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(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
BQ4845S-A4NTRG4 功能描述:實(shí)時(shí)時(shí)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(shí)間格式:HH:MM:SS RTC 存儲(chǔ)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(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
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