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参数资料
| 型号： | DS12CR885 |
| 厂商： | Maxim Integrated Products, Inc. |
| 英文描述： | RTC with Constant-Voltage Trickle Charger |
| 中文描述： | 时钟与恒压涓流充电器 |
| 文件页数： | 12/22页 |
| 文件大小： | 1093K |
| 代理商： | DS12CR885 |
D
RTC with Constant-Voltage Trickle Charger
12
____________________________________________________________________
Detailed Description
The DS12R885 is a drop-in replacement for the
DS12885 RTC. The device provides 14 bytes of real-
time clock/calendar, alarm, and control/status registers
and 114 bytes of nonvolatile, battery-backed static
RAM. A time-of-day alarm, three maskable interrupts
with a common interrupt output, and a programmable
square-wave output are available. The DS12R885 also
operates in either 24-hour or 12-hour format with an
AM/PM indicator. A precision temperature-compensat-
ed circuit monitors the status of V
CC
. If a primary
power-supply failure is detected, the device automati-
cally switches to a backup supply. The backup supply
input supports either a rechargeable battery or a super
cap, and includes an integrated trickle charger. The
trickle charger is always enabled. The DS12R885 is
accessed through a multiplexed address/data bus that
supports Intel and Motorola modes.
The DS12R887 is a surface-mount package using the
DS12R885 die, a 32.768kHz crystal, and a recharge-
able battery. The device provides a real-time clock/cal-
endar, one time-of-day alarm, three maskable interrupts
with a common interrupt output, a programmable
square wave, and 114 bytes of nonvolatile, battery-
backed static RAM. The date at the end of the month is
automatically adjusted for months with fewer than 31
days, including correction for leap years. It also oper-
ates in either 24-hour or 12-hour format with an AM/PM
indicator. A precision temperature-compensated circuit
monitors the status of V
CC
. If a primary power failure is
detected, the device automatically switches to a back-
up battery included in the package. The device is
accessed through a multiplexed byte-wide interface,
which supports both Intel and Motorola modes.
The DS12CR887 EDIP integrates a DS12R885 die with
a crystal and battery. The charging circuit on the
DS12R885 die is disabled. The battery has sufficient
capacity to power the oscillator and registers for five
years in the absence of V
CC
at +25°C.
The DS12R887 BGA includes a crystal and a recharge-
able battery. A fully charged battery can power the oscil-
lator and registers (typical current at +25°C) in the
absence of V
CC
for approximately 11 days (10% of
capacity consumed) or 98 days (90% capacity con-
sumed). When the discharge depth is 10% of capacity,
the battery can be recharged up to 1,000 times. If the dis-
charge depth is 90% of capacity, the battery can be
recharged up to 30 times. Thus, the life of the device
would be approximately 30 years (11 days X 1,000
cycles) or 8 years (98 days x 30 cycles). Charging time to
full capacity is approximately two days with V
CC
applied.
Please consult related application notes for detailed
information on battery lifetime versus depth of dis-
charge, and expected product lifetime based upon
battery cycles.
Oscillator Circuit
The DS12R885 uses an external 32.768kHz crystal. The
oscillator circuit does not require any external resistors
or capacitors to operate.
Table
1 specifies several crys-
tal parameters for the external crystal.
Figure
1 shows a
functional schematic of the oscillator circuit. An enable
bit in the control register controls the oscillator.
Oscillator startup times are highly dependent upon
crystal characteristics, PC board leakage, and layout.
High ESR and excessive capacitive loads are the major
contributors to long startup times. A circuit using a
crystal with the recommended characteristics and
proper layout usually starts within one second.
An external 32.768kHz oscillator can also drive the
DS12R885. In this configuration, the X1 pin is connected
to the external oscillator signal and the X2 pin is floated.
Table
1. Crystal Specifications*
COUNTDOWN
CHAIN
X1
X2
CRYSTAL
C
L
1
C
L
2
RTC REGISTERS
DS12R885
Figure 1. Oscillator Circuit Showing Internal Bias Network
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
Nominal
Frequency
f
O
32.768
kHz
Series
Resistance
ESR
50
k
Load
Capacitance
C
L
12.5
pF
*
The crystal, traces, and crystal input pins should be isolated
from RF generating signals. Refer to
Application Note 58:
Crystal Considerations for Dallas Real-Time Clocks
for
additional specifications.
相关PDF资料 |
PDF描述 |
|---|---|
| DS12CR887 | RTC with Constant-Voltage Trickle Charger |
| DS12CR887-33 | RTC with Constant-Voltage Trickle Charger |
| DS12CR887-5 | RTC with Constant-Voltage Trickle Charger |
| DS12R885 | RTC with Constant-Voltage Trickle Charger |
| DS12R885-33 | RTC with Constant-Voltage Trickle Charger |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DS12CR887-33 | 功能描述:实时时钟 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS12CR887-33+ | 功能描述:实时时钟 RTC w/Constant V Trickle Charger RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS12CR887-5 | 功能描述:实时时钟 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS12CR887-5+ | 功能描述:实时时钟 RTC w/Constant V Trickle Charger RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS12R885-33 | 制造商:Maxim Integrated Products 功能描述:REAL TIME CLOCK MULTIPLEXED 114BYTE - Bulk |
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