29 FN6667.5 December 13, 2011 2. Add a ground trace around the device with one end terminated at the chip ground. This guard ring wil" />
參數(shù)資料
型號(hào)： ISL12020MIRZ-T
廠商： Intersil
文件頁(yè)數(shù)： 22/34頁(yè)
文件大?。?/td> 0K
描述： IC RTC/CALENDAR TEMP SNSR 20-DFN
產(chǎn)品培訓(xùn)模塊： Solutions for Industrial Control Applications
標(biāo)準(zhǔn)包裝： 4,000
類型： 時(shí)鐘/日歷
特點(diǎn)： 警報(bào)器，夏令時(shí)，閏年，SRAM
存儲(chǔ)容量： 128B
時(shí)間格式： HH:MM:SS（12/24 小時(shí)）
數(shù)據(jù)格式： YY-MM-DD-dd
接口： I²C，2 線串口
電源電壓： 2.7 V ~ 5.5 V
電壓 - 電源，電池： 1.8 V ~ 5.5 V
工作溫度： -40°C ~ 85°C
安裝類型： 表面貼裝
封裝/外殼： 20-LFDFN 裸露焊盤
供應(yīng)商設(shè)備封裝： 20-DFN（5.5x4.0）
包裝： 帶卷 (TR)
ISL12020M
29
FN6667.5
December 13, 2011
2. Add a ground trace around the device with one end
terminated at the chip ground. This guard ring will provide
termination for emitted noise in the vicinity of the RTC device.
3. Do not run a ground or power plane immediately under the
RTC. This will add capacitance to the X1/X2 pins and change
the trimmed frequency of the oscillator. Instead, try to leave a
gap in any planes under the RTC device.
.
The best way to run clock lines around the RTC is to stay outside
of the ground ring by at least a few millimeters. Also, use the
VBAT and VDD as guard ring lines as well, they can isolate clock
lines from the X1 and X2 pins. In addition, if the IRQ/FOUT pin is
used as a clock, it should be routed away from the RTC device as
well.
Measuring Oscillator Accuracy
The best way to analyze the ISL12020M frequency accuracy is to
set the IRQ/FOUT pin for a specific frequency, and look at the
output of that pin on a high accuracy frequency counter (at least
7 digits accuracy). Note that the IRQ/FOUT is an drain output and
will require a pull-up resistor.
Using the 1.0Hz output frequency is the most convenient as the
ppm error is just as shown in Equation 7:
Other frequencies may be used for measurement but the error
calculation becomes more complex.
When the proper layout guidelines above are observed, the
oscillator should start-up in most circuits in less than one second.
When testing RTC circuits, a 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. Use the FOUT output and a
frequency counter for the most accurate results.
Temperature Compensation Operation
The ISL12020M temperature compensation feature needs to be
enabled by the user. This must be done in a specific order as
follows.
1. Read register 0Dh, the BETA register. This register contains
the 5-bit BETA trimmed value, which is automatically loaded
on initial power-up. Mask off the 5LSB’s of the value just read.
2. Bit 7 of the BETA register is the master enable control for
temperature sense operation. Set this to “1” to allow
continuous temperature frequency correction. Frequency
correction will then happen every 60s with VDD applied.
3. Bits 5 and 6 of the BETA register control temperature
compensation in battery-backup mode (see Table 16 on
page 21). Set the values for the operation desired.
4. Write back to register 0Dh making sure not to change the 5
LSB values, and include the desired compensation control
bits.
Note that every time the BETA register is written with the TSE bit
= 1, a temperature compensation cycle is instigated and a new
correction value will be loaded into the FATR/FDTR registers (if
the temperature changed since the last conversion).
Also note that registers 0Bh and 0Ch, the ITR0 and ALPHA
registers, should not be changed. If they must be written be sure
to write the same values that are recalled from initial power-up.
The ITR0 register may be written if the user wishes to re-calibrate
the oscillator frequency at room temperature for aging or board
mounting. The original recalled value can be re-written if desired
after testing.
Daylight Savings Time (DST) Example
DST involves setting the forward and back times and allowing the
RTC device to automatically advance the time or set the time
back. This can be done for current year, and future years. Many
regions have DST rules that use standard months, weeks and
time of the day, which permit a pre-programmed, permanent
setting.
An example setup for the ISL12020M is in Table 28.
FIGURE 22. SUGGESTED LAYOUT FOR ISL12020M
FOUT
SCL
SDA
GROUND
RING
ppm error
F
OUT
1
–
1e6
=
(EQ. 7)
TABLE 28. DST EXAMPLE
VARIABLE
VALUE
REGISTER
VALUE
Month Forward and DST
Enable
April
15h
84h
Week and Day Forward
and select Day/Week, not
Date
1st Week and
Sunday
16h
48h
Date Forward
not used
17h
00h
Hour Forward
2am
18h
02h
Month Reverse
October
19h
10h
Week and Day Reverse
and select Day/Week, not
Date
Last Week and
Sunday
1Ah
78h
Date Reverse
not used
1Bh
00h
Hour Reverse
2am
1Ch
02h
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ISL12021 制造商:INTERSIL 制造商全稱:Intersil Corporation 功能描述:Real Time Clock with On Chip Temp Compensation 【5ppm
ISL12021CVZ 功能描述:IC RTC LP BATT BACK SRAM 14TSSOP RoHS:是 類別:集成電路 (IC) >> 時(shí)鐘/計(jì)時(shí) - 實(shí)時(shí)時(shí)鐘 系列:- 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- 類型:時(shí)鐘/日歷 特點(diǎn):警報(bào)器，閏年，SRAM 存儲(chǔ)容量:- 時(shí)間格式:HH:MM:SS（12/24 小時(shí)） 數(shù)據(jù)格式:YY-MM-DD-dd 接口:SPI 電源電壓:2 V ~ 5.5 V 電壓 - 電源，電池:- 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-WDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:8-TDFN EP 包裝:管件
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