參數(shù)資料
型號(hào)： DS14285
廠(chǎng)商： DALLAS SEMICONDUCTOR
元件分類(lèi)： XO, clock
英文描述： Real Time Clock with NV RAM Control(帶非易失性RAM控制的實(shí)時(shí)時(shí)鐘)
中文描述： 1 TIMER(S), REAL TIME CLOCK, PDIP24
封裝： DIP-24
文件頁(yè)數(shù)： 4/23頁(yè)
文件大?。?/td> 170K
代理商： DS14285
DS14285/DS14287
022798 4/23
POWER–DOWN/POWER–UP
CONSIDERATIONS
The Real Time Clock function will continue to operate
and all of the RAM, time, calendar, and alarm memory
locations remain nonvolatile regardless of the level of
the V
CC
input. When V
CC
is applied to the
DS14285/DS14287 and reaches a level of greater than
4.25 volts (typical), the device becomes accessible after
200 ms, provided that the oscillator is running and the
oscillator countdown chain is not in reset (see Register
A). This time period allows the system to stabilize after
power is applied. When V
CC
falls below 4.25 volts (typi-
cal), the chip select input is internally forced to an inac-
tive level regardless of the value of CS at the input pin.
The DS14285/DS14287 is, therefore, write-protected.
When the DS14285/DS14287 is in a write-protected
state, all inputs are ignored and all outputs are in a high
impedance state. When V
CC
falls below a level of
approximately 3 volts, the external V
CC
supply is
switched off and an internal lithium energy source sup-
plies power to the Real Time Clock and the RAM
memory.
An external SRAM can be made nonvolatile by using the
V
CCO
and SRAM chip enable pins (see Figure 2). Non-
volatile control of the external SRAM is analogous to
that of the real–time clock registers. When V
CC
slews
down during a power fail, CEO is driven to an inactive
level regardless CEI. This write protection occurs when
V
CC
is less than 4.25 volts (typical).
During power up, when V
CC
reaches a level of greater
than 4.25 volts (typical), CEO will reflect CEI after 200
ms. During power–valid operation, the CEI input is
passed to the CEO output with a propagation delay of
less than 10 ns.
When V
CC
is above a level of approximately 3V, the
external SRAM will be powered by V
CC
through the
V
CCO
pin. When V
CC
is below a level of approximately
3V, the external SRAM will be powered by the internal
lithium cell through the V
CCO
pin. An internal compara-
tor and switch determine whether V
CCO
is powered by
V
CC
or the internal lithium cell.
When the device is in battery backup mode, the energy
source connected to the V
BAT
pin in the case of the
DS14285, or the internal lithium cell in the case of the
DS14287 can power an external SRAM for an extended
period of time. The amount of time that the lithium cell
can supply power to the external SRAM is a function of
the data retention current of the SRAM. The capacity of
the lithium cell that is encapsulated within the DS14287
module is 130 mAh. If a SRAM with a data retention cur-
rent of less than 1
μ
A is used and the oscillator current is
300 nA (typical), the cumulative data retention time is
calculated at more than 11 years.
SIGNAL DESCRIPTIONS
GND, V
CC
– DC power is provided to the device on
these pins. V
CC
is the +5 volt input. When 5 volts are
applied within normal limits, the device is fully accessi-
ble and data can be written and read. When V
CC
is
below 4.25 volts typical, reads and writes are inhibited.
However, the timekeeping function continues unaf-
fected by the lower input voltage. As V
CC
falls below 3
volts typical, the RAM and timekeeper are switched
over to an internal lithium energy source. The timekeep-
ing function maintains an accuracy of
±
1 minute per
month at 25
°
C regardless of the voltage input on the
V
CC
pin.
SQW (Square Wave Output) – The SQW pin can output
a signal from one of 13 taps provided by the 15 internal
divider stages of the Real Time Clock. The frequency of
the SQW pin can be changed by programming Register
A as shown in Table 1. The SQW signal can be turned
on and off using the SQWE bit in Register B. The SQW
signal is not available when V
CC
is less than 4.25 volts
typical.
相關(guān)PDF資料
PDF描述
DS14287 Real Time Clock with NV RAM Control(帶非易失性RAM控制的實(shí)時(shí)時(shí)鐘)
DS1486 RAMified Watchdog Timekeeper(RAM化的看門(mén)狗計(jì)時(shí)器)
DS1486P RAMified Watchdog Timekeeper(RAM化的看門(mén)狗計(jì)時(shí)器)
DS1543 64K NV Timekeeping RAM(64K非易失性計(jì)時(shí) RAM)
DS1647 Nonvolatile Timekeeping RAM(非易失性計(jì)時(shí)RAM)
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS14285_05 制造商:DALLAS 制造商全稱(chēng):Dallas Semiconductor 功能描述:Real-Time Clock with NV RAM
DS14285+ 功能描述:實(shí)時(shí)時(shí)鐘 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線(xiàn)接口:I2C 日期格式:DW:DM:M:Y 時(shí)間格式:HH:MM:SS RTC 存儲(chǔ)容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
DS14285-DS14287 制造商:DALLAS 制造商全稱(chēng):Dallas Semiconductor 功能描述:Real Time Clock with NV RAM Control
DS14285N 功能描述:實(shí)時(shí)時(shí)鐘 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線(xiàn)接口:I2C 日期格式:DW:DM:M:Y 時(shí)間格式:HH:MM:SS RTC 存儲(chǔ)容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
DS14285N+ 功能描述:實(shí)時(shí)時(shí)鐘 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線(xiàn)接口:I2C 日期格式:DW:DM:M:Y 時(shí)間格式:HH:MM:SS RTC 存儲(chǔ)容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
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