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参数资料
| 型号： | DS1744 |
| 厂商： | DALLAS SEMICONDUCTOR |
| 元件分类： | Timer or RTC |
| 英文描述： | REAL TIME CLOCK, DMA28 |
| 封装： | 0.700 INCH, PLASTIC, MODULE, DIP-28 |
| 文件页数： | 15/18页 |
| 文件大小： | 225K |
| 代理商： | DS1744 |
DS1744/DS1744P
6 of 18
DATA RETENTION MODE
The 5-volt device is fully accessible and data can be written or read only when VCC is greater than VPF.
However, when VCC is below the power fail point, VPF, (point at which write protection occurs) the internal
clock registers and SRAM are blocked from any access. At this time the power fail reset output signal
( RST ) is driven active and will remain active until VCC returns to nominal levels. When VCC falls below
the battery switch point VSO (battery supply level), device power is switched from the VCC pin to the
backup battery. RTC operation and SRAM data are maintained from the battery until VCC is returned to
nominal levels. The 3.3 volt device is fully accessible and data can be written or read only when VCC is
greater than VPF. When VCC falls below the power fail point, VPF , access to the device is inhibited. At this
time the power fail reset output signal ( RST ) is driven active and will remain active until VCC returns to
nominal levels. If VPF is less than VSO, the device power is switched from VCC to the backup supply (VBAT)
when VCC drops below VPF. If VPF is greater than VSO, the device power is switched from VCC to the
backup supply (VBAT) when VCC drops below VSO. RTC operation and SRAM data are maintained from
the battery until VCC is returned to nominal levels. The RST signal is an open drain output and requires a
pull up. Except for the RST , all control, data, and address signals must be powered down when VCC is
powered down.
BATTERY LONGEVITY
The DS1744 has a lithium power source that is designed to provide energy for clock activity, and clock
and RAM data retention when the VCC supply is not present. The capability of this internal power supply is
sufficient to power the DS1744 continuously for the life of the equipment in which it is installed. For
specification purposes, the life expectancy is 10 years at 25
°C with the internal clock oscillator running in
the absence of VCC power. Each DS1744 is shipped from Dallas Semiconductor with its lithium energy
source disconnected, guaranteeing full energy capacity. When VCC is first applied at a level greater than
VPF , the lithium energy source is enabled for battery backup operation. Actual life expectancy of the
DS1744 will be much longer than 10 years since no lithium battery energy is consumed when VCC is
present.
BATTERY MONITOR
The DS1744 constantly monitors the battery voltage of the internal battery. The Battery Flag bit (bit 7) of
the day register is used to indicate the voltage level range of the battery. This bit is not writable and should
always be a one when read. If a zero is ever present, an exhausted lithium energy source is indicated and
both the contents of the RTC and RAM are questionable.
相关PDF资料 |
PDF描述 |
|---|---|
| DS1746-70 | 0 TIMER(S), REAL TIME CLOCK, DIP32 |
| DS1746WP-120 | 0 TIMER(S), REAL TIME CLOCK, DMA34 |
| DS1746W-120 | 0 TIMER(S), REAL TIME CLOCK, DIP32 |
| DS1746P-70 | 0 TIMER(S), REAL TIME CLOCK, DMA34 |
| DS1746 | REAL TIME CLOCK, DMA32 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DS1744_10 | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Y2K-Compliant, Nonvolatile Timekeeping RAMs |
| DS1744_1203 | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Y2K-Compliant, Nonvolatile Timekeeping RAMs |
| DS1744-70 | 功能描述:实时时钟 Timekeeping NV RAM 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 |
| DS1744-70+ | 功能描述:实时时钟 Timekeeping NV RAM 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 |
| DS1744-70IND | 功能描述:实时时钟 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 |
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