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参数资料
| 型号： | DS1557WP-120IND+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/17页 |
| 文件大小： | 0K |
| 描述： | IC RTC RAM Y2K 3.3V 120NS 34PCM |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 40 |
| 类型： | 时钟/日历 |
| 特点： | 警报器，闰年，NVSRAM，监视计时器，Y2K |
| 存储容量： | 512KB |
| 时间格式： | HH:MM:SS（24 小时） |
| 数据格式： | YY-MM-DD-dd |
| 接口： | 并联 |
| 电源电压： | 2.97 V ~ 3.63 V |
| 电压 - 电源，电池： | 3V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 34-PowerCap? 模块 |
| 供应商设备封装： | 34-PowerCap 模块 |
| 包装： | 管件 |
DS1557 4Meg, Nonvolatile, Y2K-Compliant Timekeeping RAM
4 of 17
DATA WRITE MODE
The DS1557 is in the write mode whenever
WE and CE are in their active state. The start of a write is
referenced to the latter occurring transition of
WE or CE. The addresses must be held valid throughout
the cycle.
CE and WE must return inactive for a minimum of t
WR prior to the initiation of a subsequent
read or write cycle. Data in must be valid tDS prior to the end of the write and remain valid for tDH
afterward. In a typical application, the
OE signal will be high during a write cycle. However, OE can be
active provided that care is taken with the data bus to avoid bus contention. If
OE is low prior to WE
transitioning low, the data bus can become active with read data defined by the address inputs. A low
transition on
WE will then disable the outputs t
WEZ after WE goes active.
DATA RETENTION MODE
The 5V device is fully accessible and data can be written and 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. When VCC falls below the battery switch
point VSO (battery supply level), device power is switched from the VCC pin to the internal backup lithium
battery. RTC operation and SRAM data are maintained from the battery until VCC is returned to nominal
levels.
The 3.3V device is fully accessible and data can be written and read only when VCC is greater than VPF.
When VCC falls below VPF, access to the device is inhibited. If VPF is less than VSO, the device power is
switched from VCC to the internal backup lithium battery when VCC drops below VPF. If VPF is greater
than VSO, the device power is switched from VCC to the internal backup lithium battery when VCC drops
below VSO. RTC operation and SRAM data are maintained from the battery until VCC is returned to
nominal levels.
All control, data, and address signals must be powered down when VCC is powered down.
BATTERY LONGEVITY
The DS1557 has a lithium power source that is designed to provide energy for the 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 DS1557 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.
INTERNAL BATTERY MONITOR
The DS1557 constantly monitors the battery voltage of the internal battery. The Battery Low Flag (BLF)
bit of the Flags Register (B4 of 7FFF0h) is not writable and should always be a 0 when read. If a 1 is ever
present, an exhausted lithium energy source is indicated and both the contents of the RTC and RAM are
questionable.
POWER-ON RESET
A temperature compensated comparator circuit monitors the level of VCC. When VCC falls to the power
fail trip point, the
RST signal (open drain) is pulled low. When V
CC returns to nominal levels, the RST
signal continues to be pulled low for a period of 40 ms to 200 ms. The power-on reset function is
independent of the RTC oscillator and thus is operational whether or not the oscillator is enabled.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS1557WP-120IND+ | 功能描述:实时时钟 4M NV RAM Timekeeper 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 |
| DS1557WP-150 | 制造商:DALLAS 制造商全称:Dallas Semiconductor 功能描述:4MEG NV Y2KC Timekeeping RAM |
| DS1558 | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Watchdog Clock with NV RAM Control |
| DS1558B | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Watchdog Clock with NV RAM Control |
| DS1558D | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Watchdog Clock with NV RAM Control |
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