NV RAMコントロール付き、リアルタイムクロック

型番	ステータス	推奨置換品	説明
DS14285	この製品は製造を中止しています。推奨置換品についてはオーダー情報をご覧ください。	DS1685 DS17285 DS17485 DS17885	直接置換品はありません。DS17x85は2K、4K、および8Kバイトの拡張RAMを備えています。
DS14287	この製品は製造を中止しています。推奨置換品についてはオーダー情報をご覧ください。	DS1687 DS17287 DS17487 DS17887	直接置換品はありません。DS17x87は2K、4K、および8Kバイトの拡張RAMを備えています。

The DS14285/DS14287 real-time clock with NV RAM control provides the industry standard DS1287 clock function with the additional feature of providing nonvolatile control for an external SRAM. Functions include a nonvolatile time-of-day clock, alarm, 100-year calendar, programmable interrupt, square wave generator, and 114 bytes of nonvolatile static RAM. For the DS14287 a lithium energy source, quartz crystal, and write protection circuitry are contained within a 24-pin dual in-line package. The DS14285 requires an external quartz crystal connected to the X1 and X2 pins as well as an external energy source connected to the V_BAT pin. A standard 32.768kHz quartz crystal can be directly connected to the DS14285 via pins 1 and 2 (X1, X2). The crystal selected for use should have a specified load capacitance (C_L) of 6pF. For more information on crystal selection and crystal layout considerations, please consult Application Note 58, Crystal Considerations with Dallas Real-time Clocks.

The DS14285/DS14287 uses its backup energy source and battery-backup controller to make a standard CMOS static RAM nonvolatile during power-fail conditions. During power fail, the DS14285/DS14287 automatically write-protects the external SRAM and provides a V_CC output sourced from its internal battery.

For the DS14287 the internal lithium cell is electrically isolated from the clock and memory when shipped from the factory. This isolation is removed after the first application of V_CC, allowing the lithium cell to provide data retention to the clock, internal RAM, V_CCO and active-low CEO on subsequent power-downs. Care must be taken after this isolation has been broken to avoid inadvertently discharging the lithium cell through the V_CCO and active-low CEO pins.

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