參數(shù)資料
型號： M41T82RQA6F
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, QCC16
封裝： 4 X 4 MM, ROHS COMPLIANT, QFN-16
文件頁數(shù)： 24/58頁
文件大小： 462K
代理商： M41T82RQA6F
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
CXO, connected from the XI and XO pins to ground (see Figure 16 on page 27). The
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
M41T82RMY6F 1 TIMER(S), REAL TIME CLOCK, PDSO18
M41T82SQA6F 1 TIMER(S), REAL TIME CLOCK, QCC16
M41T83RM6F 1 TIMER(S), REAL TIME CLOCK, PDSO8
M41T83ZM6E 1 TIMER(S), REAL TIME CLOCK, PDSO8
M41T83ZQA6E 1 TIMER(S), REAL TIME CLOCK, QCC16
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
M41T82SM6E 功能描述:實(shí)時時鐘 Serial I2C bus 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(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
M41T82SM6F 功能描述:實(shí)時時鐘 Serial I2C bus 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(fēng)格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube
M41T82SMY6E 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Serial RTC with battery switchover
M41T82SMY6F 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Serial RTC with battery switchover
M41T82SQ6E 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Serial RTC with battery switchover
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