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參數(shù)資料
| 型號： | DS17485 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 3 Volt/5 Volt Real Time Clock(3V/5V實時時鐘) |
| 文件頁數(shù)： | 5/32頁 |
| 文件大?。?/td> | 236K |
| 代理商： | DS17485 |
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DS17485/DS17487
030598 5/32
DS17485 ONLY
X1, X2 –
Connections for a standard 32.768 KHz quartz
crystal. For greatest accuracy, the DS17485 must be
used with a crystal that has a specified load capacitance
of either 6 pF or 12.5 pF. The Crystal Select (CS) bit in
Extended Control Register 4B is used to select opera-
tion with a 6 pF or 12.5 pF 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 on crystal selection and crystal
layout considerations, please consult Application Note
58, “Crystal Considerations with Dallas Real Time
Clocks”. The DS17485 can also be driven by an exter-
nal 32.768 KHz 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 3 Volt lithium cell
or other energy source. Battery voltage must be held
between 2.5 and 3.7 volts for proper operation.
POWER–DOWN/POWER–UP
CONSIDERATIONS
The real–time clock function will continue to operate and
all of the RAM, time, calendar, and alarm memory loca-
tions remain nonvolatile regardless of the level of the
V
CC
input.
When
V
CC
DS17485/DS17487 and reaches a level of greater than
V
PF
(power fail trip point), the device becomes accessi-
ble after t
REC
, provided that the oscillator is running and
the oscillator countdown chain is not in reset (see Regis-
ter A). This time period allows the system to stabilize
after power is applied.
is
applied
to
the
The DS17485/DS17487 is available in either a 3 volt or
a 5 volt device.
The 5 volt device is fully accessible and data can be writ-
ten and read only when V
CC
is greater than 4.5 volts.
When V
CC
is below 4.5 volts, read and writes are inhib-
ited. 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 con-
nected either to the V
BAT
pin or V
BAUX
pin.
The 3 volt device is fully accessible and data can be writ-
ten or read only when V
CC
is greater than 2.7 volts.
When V
CC
falls below V
PF
, access to the device is inhib-
ited. If V
PF
is less than V
BAT
and V
BAUX
, the power sup-
ply is switched from V
CC
to the backup supply (the
greater of V
BAT
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.
RTC ADDRESS MAP
The address map for the RTC registers of the
DS17485/DS17487 is shown in Figure 2. The address
map consists of the 14 clock/calendar registers. Ten
registers contain the time, calendar, and alarm data,
and four bytes are used for control and status. All regis-
ters can be directly written or read except for the follow-
ing:
1. Registers C and D are read–only.
2. Bit 7 of Register A is read–only.
3. The high order bit of the seconds byte is read–only.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| DS17485-3 | 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 |
| DS17485-3+ | 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 |
| DS17485-5 | 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 |
| DS17485-5+ | 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 |
| DS1748555 | 制造商:Maxim Integrated Products 功能描述: |
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