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參數(shù)資料
| 型號： | M41T82RMY6E |
| 廠商： | STMICROELECTRONICS |
| 元件分類： | 時鐘/數(shù)據(jù)恢復(fù)及定時提取 |
| 英文描述： | 1 TIMER(S), REAL TIME CLOCK, PDSO18 |
| 封裝： | 0.300 INCH, ROHS COMPLIANT, PLASTIC, SOP-18 |
| 文件頁數(shù)： | 24/58頁 |
| 文件大小： | 462K |
| 代理商： | M41T82RMY6E |
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Clock operation
M41T82 M41T83
3.4.2
Analog calibration (programmable load capacitance)
A second method of calibration employs the use of programmable internal load capacitors to
adjust (or trim) the oscillator frequency.
By design, the oscillator is intended to be 0 ppm ± crystal accuracy at room temperature
(25°C, see Figure 17 on page 31). For a 12.5 pF crystal, the default loading on each side of
the crystal will be 25 pF. For incrementing or decrementing the calibration value,
capacitance will be added or removed in increments of 0.25 pF to each side of the crystal.
Internally, CLOAD of the oscillator is changed via two digitally controlled capacitors, CXI and
effective on-chip series load capacitance, CLOAD, ranges from 3.5 pF to 17.4 pF, with a
nominal value of 12.5 pF (AC0-AC6 = ‘0’).
The effective series load capacitance (CLOAD) is the combination of CXI and CXO:
Seven analog calibration bits, AC0 to AC6, are provided in order to adjust the on-chip load
capacitance value for frequency compensation of the RTC. Each bit has a different weight
for capacitance adjustment. An Analog Calibration Sign (ACS) bit determines if capacitance
is added (ACS bit = ‘0’, negative calibration) or removed (ACS bit = ‘1’, positive calibration).
The majority of the calibration adjustment is positive (i.e. to increase the oscillator frequency
by removing capacitance) due to the typical characteristic of quartz crystals to slow down
due to changes in temperature, but negative calibration is also available.
Since the Analog Calibration Register adjustment is essentially “pulling” the frequency of the
oscillator, the resulting frequency changes will not be linear with incremental capacitance
changes. The equations which govern this mechanism indicate that smaller capacitor values
of Analog Calibration adjustment will provide larger increments. Thus, the larger values of
Analog Calibration adjustment will produce smaller incremental frequency changes. These
values typically vary from 6-10 ppm/bit at the low end to <1 ppm/bit at the highest
capacitance settings. The range provided by the Analog Calibration Register adjustment
with a typical surface mount crystal is approximately ±30 ppm around the AC6-AC0 = 0
default setting because of this property (see Table7 on page31).
C
LOAD
11 C
XI
1C
XO
+
()
=
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| M41T82ZQA6E | 1 TIMER(S), REAL TIME CLOCK, QCC16 |
| M41T82RQA6F | 1 TIMER(S), REAL TIME CLOCK, QCC16 |
| M41T82RMY6F | 1 TIMER(S), REAL TIME CLOCK, PDSO18 |
| M41T82SQA6F | 1 TIMER(S), REAL TIME CLOCK, QCC16 |
| M41T83RM6F | 1 TIMER(S), REAL TIME CLOCK, PDSO8 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| M41T82RMY6F | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Serial RTC with battery switchover |
| M41T82RQ6E | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Serial RTC with battery switchover |
| M41T82RQ6F | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Serial RTC with battery switchover |
| M41T82RQA6E | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Serial I2C bus RTC with battery switchover |
| M41T82RQA6F | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Serial I2C bus RTC with battery switchover |
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