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參數(shù)資料
型號(hào): DS1746P-70
廠商: Maxim Integrated Products
文件頁數(shù): 14/16頁
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描述: IC RTC RAM Y2K 5V 70NS 34-PCM
標(biāo)準(zhǔn)包裝: 40
類型: 時(shí)鐘/日歷
特點(diǎn): 閏年,NVSRAM,Y2K
存儲(chǔ)容量: 128KB
時(shí)間格式: HH:MM:SS(24 小時(shí))
數(shù)據(jù)格式: YY-MM-DD-dd
接口: 并聯(lián)
電源電壓: 4.5 V ~ 5.5 V
電壓 - 電源,電池: 3V
工作溫度: 0°C ~ 70°C
安裝類型: 表面貼裝
封裝/外殼: 34-PowerCap? 模塊
供應(yīng)商設(shè)備封裝: 34-PowerCap 模塊
包裝: 管件
DS1746/DS1746P Y2K-Compliant, Nonvolatile Timekeeping RAMs
7 of 16
DATA-RETENTION MODE
The 5V 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 3.3V 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 DS1746 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 DS1746 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 DS1746 is shipped from Maxim 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 DS1746 will
be much longer than 10 years since no lithium battery energy is consumed when VCC is present.
BATTERY MONITOR
The DS1746 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.
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