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参数资料
| 型号： | 71M6513-IGTR/F |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PQFP100 |
| 封装： | LEAD FREE, LQFP-100 |
| 文件页数： | 84/104页 |
| 文件大小： | 1390K |
| 代理商： | 71M6513-IGTR/F |
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71M6513/71M6513H
3-Phase Energy Meter IC
DATA SHEET
AUGUST 2011
Page: 80 of 104
2005-2011 Teridian Semiconductor Corporation
A Maxim Integrated Products Brand
Temperature Compensation and Mains Frequency Stabilization for the RTC
The accuracy of the RTC depends on the stability of the external crystal. Crystals vary in terms of initial accuracy as well as in
terms of behavior over temperature. The flexibility provided by the MPU allows for compensation of the RTC using the sub-
strate temperature. To achieve this, the crystal has to be characterized over temperature and the three coefficients Y_CAL,
Y_CALC, and Y_CAL_C2 have to be calculated. Provided the IC substrate temperatures tracks the crystal temperature, the
coefficients can be used in the MPU firmware to trigger occasional corrections of the RTC seconds count, using the
RTC_DEC_SEC or RTC_INC_SEC registers in I/O RAM.
It is not recommended to measure crystal frequency directly due to the error introduced by the measurement probes. A
practical method to measure the crystal frequency (when installed on the PCB with the 71M6513) is to have a DIO pin toggle
every second, based on the RTC interrupt, with all other interrupts disabled. When this signal is measured with a precision
timer, the crystal frequency can be obtained from the measured time period t (in s):
t
s
f
6
10
32768
=
Example: Let us assume a crystal characterized by the measurements shown in Table 61. The values show that even at
nominal temperature (the temperature at which the chip was calibrated for energy), the deviation from the ideal crystal
frequency is 11.6 PPM, resulting in about one second inaccuracy per day, i.e. more than some standards allow.
Deviation from
Nominal
Temperature [°C]
Measured
Frequency [Hz]
Deviation from
Nominal
Frequency [PPM]
+50
32767.98
-0.61
+25
32768.28
8.545
0
32768.38
11.597
-25
32768.08
2.441
-50
32767.58
-12.817
Table 61: Frequency over Temperature
As Figure 29 shows, even a constant compensation would not bring much improvement, since the temperature characteristics
of the crystal are a mix of constant, linear, and quadratic effects (in commercially available crystals, the constant and quadratic
effects are dominant).
Figure 29: Crystal Frequency over Temperature
The temperature characteristics of the crystal are obtained from the curve in Figure 29 by curve-fitting the PPM deviations. A
fairly close curve fit is achieved with the coefficients a = 10.89, b = 0.122, and c = –0.00714 (see Figure 30).
32767.5
32767.6
32767.7
32767.8
32767.9
32768
32768.1
32768.2
32768.3
32768.4
32768.5
-50
-25
0
25
50
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 71M6515H | 制造商:TERIDIAN 制造商全称:TERIDIAN 功能描述:Energy Meter IC |
| 71M6515H_11 | 制造商:TERIDIAN 制造商全称:TERIDIAN 功能描述:Up to 10ppmC precision ultra-stable voltage reference Digital temperature compensation |
| 71M6515H-DB | 功能描述:开发板和工具包 - 8051 71M6515H Demo Brd RoHS:否 制造商:Silicon Labs 产品:Development Kits 工具用于评估:C8051F960, Si7005 核心: 接口类型:USB 工作电源电压: |
| 71M6515H-IGT | 制造商:Maxim Integrated Products 功能描述:METERING FRONT END - Rail/Tube |
| 71M6515H-IGT/F | 功能描述:计量片上系统 - SoC Energy Meter IC RoHS:否 制造商:Maxim Integrated 核心:80515 MPU 处理器系列:71M6511 类型:Metering SoC 最大时钟频率:70 Hz 程序存储器大小:64 KB 数据 RAM 大小:7 KB 接口类型:UART 可编程输入/输出端数量:12 片上 ADC: 安装风格:SMD/SMT 封装 / 箱体:LQFP-64 封装:Reel |
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