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参数资料
| 型号： | M48T37V-10MH1TR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 时钟/数据恢复及定时提取 |
| 英文描述： | 0 TIMER(S), REAL TIME CLOCK, PDSO44 |
| 封装： | 0.330 INCH, ROHS COMPLIANT, PLASTIC, SOH-44 |
| 文件页数： | 7/30页 |
| 文件大小： | 515K |
| 代理商： | M48T37V-10MH1TR |
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M48T37Y, M48T37V
Clock operations
Doc ID 7019 Rev 9
Figure 8.
Backup mode alarm waveforms
3.5
Calibrating the clock
The M48T37Y/V is driven by a quartz controlled oscillator with a nominal frequency of
32,768 Hz. The devices are tested not to exceed ±35 ppm (parts per million) oscillator
frequency error at 25 °C, which equates to about ±1.53 minutes per month. With the
calibration bits properly set, the accuracy of each M48T37Y/V improves to better than
+1/–2 ppm at 25 °C.
The oscillation rate of any crystal changes with temperature (see Figure 10 on page 19).
Most clock chips compensate for crystal frequency and temperature shift error with
cumbersome trim capacitors. The M48T37Y/V design, however, employs periodic counter
correction. The calibration circuit adds or subtracts counts from the oscillator divider circuit
at the divide by 256 stage, as shown in Figure 11 on page 19. The number of times pulses
are blanked (subtracted, negative calibration) or split (added, positive calibration) depends
upon the value loaded into the five-bit calibration byte found in the control register. Adding
counts speeds the clock up, subtracting counts slows the clock down.
The calibration byte occupies the five lower order bits (D4-D0) in the control register 7FF8h.
These bits can be set to represent any value between 0 and 31 in binary form. Bit D5 is the
sign bit; '1' indicates positive calibration, '0' indicates negative calibration. Calibration occurs
within a 64 minute cycle. The first 62 minutes in the cycle may, once per minute, have one
second either shortened by 128 or lengthened by 256 oscillator cycles. If a binary '1' is
loaded into the register, only the first 2 minutes in the 64 minute cycle will be modified; if a
binary 6 is loaded, the first 12 will be affected, and so on.
Therefore, each calibration step has the effect of adding 512 or subtracting 256 oscillator
cycles for every 125, 829, 120 (64 minutes x 60 seconds/minute x 32,768 cycles/second)
actual oscillator cycles, that is +4.068 or –2.034 ppm of adjustment per calibration step in
the calibration register. Assuming that the oscillator is in fact running at exactly 32,768 Hz,
each of the 31 increments in the calibration byte would represent +10.7 or –5.35 seconds
per month which corresponds to a total range of +5.5 or –2.75 minutes per month.
AI03254B
VCC
IRQ/FT
tREC
VPFD (max)
VPFD (min)
ABE, AFE bit in Interrupt Register
AF bit in Flags Register
HIGH-Z
VSO
HIGH-Z
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相关代理商/技术参数 |
参数描述 |
|---|---|
| M48T37V-10MH6 | 功能描述:实时时钟 256K (32Kx8) 100ns 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 |
| M48T37V-10MH6E | 功能描述:实时时钟 256K (32Kx8) 100ns 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 |
| M48T37V-10MH6F | 功能描述:实时时钟 256K (32Kx8) 100ns 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 |
| M48T37V-10MH6TR | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:3.3V-5V 256 Kbit 32Kb x8 TIMEKEEPER SRAM |
| M48T37V-70MH1 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:3.3V-5V 256 Kbit 32Kb x8 TIMEKEEPER SRAM |
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