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參數(shù)資料
| 型號： | ISL12025 |
| 廠商： | Intersil Corporation |
| 英文描述： | Real-Time Clock/Calendar with EEPROM(EEPROM實(shí)時(shí)時(shí)鐘/日歷) |
| 中文描述： | 實(shí)時(shí)時(shí)鐘/日歷（EEPROM的實(shí)時(shí)時(shí)鐘/日歷帶有EEPROM） |
| 文件頁數(shù)： | 22/27頁 |
| 文件大?。?/td> | 412K |
| 代理商： | ISL12025 |
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22
FN6371.2
October 19, 2007
For more detailed operation, see Intersil’s application note
AN154 on Intersil’s website at www.intersil.com.
Layout Considerations
The crystal input at X1 has a very high impedance and will
pick up high frequency signals from other circuits on the
board. Since the X2 pin is tied to the other side of the crystal,
it is also a sensitive node. These signals can couple into the
oscillator circuit and produce double clocking or
mis-clocking, seriously affecting the accuracy of the RTC.
Care needs to be taken in layout of the RTC circuit to avoid
noise pickup. Figure 27 shows a suggested layout for the
ISL12025 or ISL12027 devices.
The X1 and X2 connections to the crystal are to be kept as
short as possible. A thick ground trace around the crystal is
advised to minimize noise intrusion, but ground near the X1
and X2 pins should be avoided as it will add to the load
capacitance at those pins. Keep in mind these guidelines for
other PCB layers in the vicinity of the RTC device. A small
decoupling capacitor at the V
DD
pin of the chip is mandatory,
with a solid connection to ground (Figure 27).
Oscillator Measurements
When a proper crystal is selected and the layout guidelines
above are observed, the oscillator should start up in most
circuits in less than one second. Some circuits may take
slightly longer, but startup should definitely occur in less than
5s. When testing RTC circuits, the most common impulse is
to apply a scope probe to the circuit at the X2 pin (oscillator
output) and observe the waveform. DO NOT DO THIS!
Although in some cases you may see a usable waveform,
due to the parasitics (usually 10pF to ground) applied with
the scope probe, there will be no useful information in that
waveform other than the fact that the circuit is oscillating.
The X2 output is sensitive to capacitive impedance so the
voltage levels and the frequency will be affected by the
parasitic elements in the scope probe. Applying a scope
probe can possibly cause a faulty oscillator to start-up,
hiding other issues (although in the Intersil RTC’s, the
internal circuitry assures startup when using the proper
crystal and layout).
The best way to analyze the RTC circuit is to power it up and
read the real-time clock as time advances. Alternatively the
frequency can be checked by setting an alarm for each
TABLE 7. CRYSTAL PARAMETERS REQUIRED FOR INTERSIL RTC’S
PARAMETER
MIN
TYP
MAX
UNITS
NOTES
Frequency
32.768
kHz
Frequency Tolerance
±100
ppm
Down to 20ppm if desired
Turnover Temperature
20
25
30
°C
Typically the value used for most crystals
Operating Temperature Range
-40
85
°C
Parallel Load Capacitance
12.5
pF
Equivalent Series Resistance
50
k
Ω
For best oscillator performance
TABLE 8. CRYSTAL MANUFACTURERS
MANUFACTURER
PART NUMBER
TEMP RANGE
+25°C FREQUENCY TOLERANCE
Citizen
CM201, CM202, CM200S
-40 to +85°C
±20ppm
Epson
MC-405, MC-406
-40 to +85°C
±20ppm
Raltron
RSM-200S-A or B
-40 to +85°C
±20ppm
SaRonix
32S12A or B
-40 to +85°C
±20ppm
Ecliptek
ECPSM29T-32.768K
-10 to +60°C
±20ppm
ECS
ECX-306/ECX-306I
-10 to +60°C
±20ppm
Fox
FSM-327
-40 to +85°C
±20ppm
FIGURE 27. SUGGESTED LAYOUT FOR INTERSIL RTC IN SO-8
ISL12025
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| ISL12025IBZ | 功能描述:實(shí)時(shí)時(shí)鐘 REAL TIME CLK/CLNDR W/EEPROM 2 63VSET 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(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 |
| ISL12025IBZ-T | 功能描述:實(shí)時(shí)時(shí)鐘 REAL TIME CLK/CLNDR W/EEPROM 2 63VSET 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(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 |
| ISL12025IVZ | 功能描述:實(shí)時(shí)時(shí)鐘 REAL TIME CLK/CLNDR W/EEPROM 2 63SET 8 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(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 |
| ISL12025IVZ-T | 功能描述:實(shí)時(shí)時(shí)鐘 REAL TIME CLK/CLNDR W/EEPROM 2 63SET 8 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(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 |
| ISL12026 | 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:Real Time Clock/Calendar with I2C Bus? and EEPROM |
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