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Features
Real-Time Clock counts seconds
through years in BCD format
Integrated battery and crystal
On-chip battery-backup switch-
over circuit with nonvolatile con-
trol for an external SRAM
130mAh battery capacity
±1 minute per month clock accu-
racy
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 bq4847 Real-Time Clock Mod-
ule is a low-power microprocessor
peripheral that integrates a time-
of-day clock, a 100-year calendar, a
CPU supervisor, a battery, and a crys-
tal in a 28-pin DIP module. The part
is ideal for fax machines, copiers, in-
dustrial control systems, point-of-sale
terminals, data loggers, and comput-
ers.
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 write-
protect 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 refer-
ence 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 microproces-
sor reset. The reset stays active
for 200ms after VCC rises within
tolerance to allow for power supply
and processor stabilization.
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.
The bq4847 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 ac-
tive 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 30.5
s
to 500ms.
1
bq4847/bq4847Y
1
PN484701.eps
28-Pin DIP Module
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
16
15
VCC
WE
CEIN
CEOUT
NC
WDI
OE
CS
NC
DQ7
DQ6
DQ5
DQ4
DQ3
VOUT
NC
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
Pin Names
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
RTC Module With CPU Supervisor
Caution:
Take care to avoid inadvertent dis-
charge through VOUT and CEOUT
after battery isolation has been
broken.
Sept. 1996
Not Recommended For New Designs
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相关代理商/技术参数
BQ4847Y-MT 制造商:TI 制造商全称:Texas Instruments 功能描述:RTC Module With CPU Supervisor
BQ4850Y 制造商:TI 制造商全称:Texas Instruments 功能描述:RTC Module With 512Kx8 NVSRAM
BQ4850Y_13 制造商:TI 制造商全称:Texas Instruments 功能描述:RTC Module With 512Kx8 NVSRAM
BQ4850YMA-85 功能描述:实时时钟 RTC Module 512Kx8 NVSRAM RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube
BQ4850YMA-85N 功能描述:实时时钟 RTC Mod With 512Kx8 NVSRAM RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube
BQ4852Y 制造商:TI 制造商全称:Texas Instruments 功能描述:RTC Module With 512Kx8 NVSRAM
BQ4852YMC-85 功能描述:实时时钟 w/512Kx8 NVSRAM Watchdog Timer RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube
BQ48S1.5-30A 制造商:未知厂家 制造商全称:未知厂家 功能描述:DC to DC Converter