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參數資料
| 型號： | DS17485E-3 |
| 英文描述： | 3V/5V Real-Time Clock |
| 中文描述： | 3V/5V實時時鐘 |
| 文件頁數： | 6/38頁 |
| 文件大?。?/td> | 427K |
| 代理商： | DS17485E-3 |
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DS17485/DS17487
6 of 38
DS17485 ONLY
X1, X2 –
Connections for a standard 32.768kHz quartz crystal. For greatest accuracy, the DS17485 must
be used with a crystal that has a specified load capacitance of either 6pF or 12.5pF. The crystal select
(CS) bit in extended-control register 4B is used to select operation with a 6pF or 12.5pF crystal. The
crystal is attached directly to the X1 and X2 pins. There is no need for external capacitors or resistors.
Note: X1 and X2 are very high-impedance nodes. It is recommended that they and the crystal be guard-
ringed with ground and that high frequency signals be kept away from the crystal area.
For more information about crystal selection and crystal layout considerations, refer to
Application Note
58
, “Crystal Considerations with Dallas Real-Time Clocks.” The DS17485 can also be driven by an
external 32.768kHz oscillator. In this configuration, the X1 pin is connected to the external oscillator
signal and the X2 pin is floated.
V
BAT
–
Battery input for any standard 3V lithium cell or other energy source. Battery voltage must be
held between 2.5V and 3.7V for proper operation. UL recognized to ensure against reverse charging
current when used in conjunction with a lithium battery. See “Conditions of Acceptability” at
www.maxim-ic.com/TechSupport/AQ/ntrl.htm
.
POWER-DOWN/POWER-UP CONSIDERATIONS
The RTC function continues 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
DS17485/DS17487 and reaches a level of greater than V
PF
(power-fail trip point), the device becomes
accessible after t
REC
, provided that the oscillator is running and the oscillator countdown chain is not in
reset (Register A). This time period allows the system to stabilize after power is applied.
The DS17485/DS17487 is available in either a 3V or a 5V device.
The 5V device is fully accessible and data can be written and read only when V
CC
is greater than 4.5V.
When V
CC
is below 4.5V, read and writes are inhibited. However, the timekeeping function continues
unaffected by the lower input voltage. As V
CC
falls below the greater of V
BAT
and V
BAUX
, the RAM and
timekeeper are switched over to a lithium battery connected either to the V
BAT
pin or V
BAUX
pin.
The 3V device is fully accessible and data can be written or read only when V
CC
is greater than 2.7V.
When V
CC
falls below V
PF
, access to the device is inhibited. If V
PF
is less than V
BAT
and V
BAUX
, the
power supply is switched from V
CC
to the backup supply (the greater of
VBAT
and V
BAUX
) when V
CC
drops
below V
PF
. If V
PF
is greater than V
BAT
and V
BAUX
, the power supply is switched from V
CC
to the backup
supply when V
CC
drops below the larger of V
BAT
and V
BAUX
.
When V
CC
falls below V
PF
, the chip is write-protected. With the possible exception of the
KS
,
PWR
,
RCLR
, and SQW pins, all inputs are ignored and all outputs are in a high-impedance state.
相關PDF資料 |
PDF描述 |
|---|---|
| DS17485E-5 | 3V/5V Real-Time Clock |
| DS17485EN-3 | 3V/5V Real-Time Clock |
| DS17485EN-5 | 3V/5V Real-Time Clock |
| DS17485S-3 | 3V/5V Real-Time Clock |
| DS17485S-5 | 3V/5V Real-Time Clock |
相關代理商/技術參數 |
參數描述 |
|---|---|
| DS17485E-3+ | 功能描述:實時時鐘 3V/5V RTC RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線接口:I2C 日期格式:DW:DM:M:Y 時間格式:HH:MM:SS RTC 存儲容量: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: 安裝風格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube |
| DS17485E5 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Real-Time Clocks |
| DS17485E-5 | 功能描述:實時時鐘 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線接口:I2C 日期格式:DW:DM:M:Y 時間格式:HH:MM:SS RTC 存儲容量: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: 安裝風格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube |
| DS17485E-5+ | 功能描述:實時時鐘 3V/5V RTC RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線接口:I2C 日期格式:DW:DM:M:Y 時間格式:HH:MM:SS RTC 存儲容量: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: 安裝風格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube |
| DS17485EN-3 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:3V/5V Real-Time Clock |
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