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DS1339U-33+ 参数 Datasheet PDF下载

DS1339U-33+图片预览
型号: DS1339U-33+
PDF下载: 下载PDF文件 查看货源
内容描述: I²C串行实时时钟 [I2C Serial Real-Time Clock]
分类和应用: 外围集成电路光电二极管时钟
文件页数/大小: 18 页 / 280 K
品牌: DALLAS [ DALLAS SEMICONDUCTOR ]
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DS1339 I2C Serial Real-Time Clock  
DETAILED DESCRIPTION  
The DS1339 serial real-time clock (RTC) is a low-power clock/date device with two programmable time-of-day  
alarms and a programmable square-wave output. Address and data are transferred serially through an I2C bus.  
The clock/date provides seconds, minutes, hours, day, date, month, and year information. The date at the end of  
the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The  
clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The DS1339 has a built-in power-  
sense circuit that detects power failures and automatically switches to the backup supply, maintaining time and  
date operation.  
OPERATION  
The DS1339 operates as a slave device on the serial bus. Access is obtained by implementing a START condition  
and providing a device identification code followed by data. Subsequent registers can be accessed sequentially  
until a STOP condition is executed. The device is fully accessible and data can be written and read when VCC is  
greater than VPF. However, when VCC falls below VPF, the internal clock registers are blocked from any access. If  
VPF is less than VBACKUP, the device power is switched from VCC to VBACKUP when VCC drops below VPF. If VPF is  
greater than VBACKUP, the device power is switched from VCC to VBACKUP when VCC drops below VBACKUP. The  
registers are maintained from the VBACKUP source until VCC is returned to nominal levels. The block diagram in  
Figure 3 shows the main elements of the serial real-time clock.  
OSCILLATOR CIRCUIT  
The DS1339 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or  
capacitors to operate. Table 1 specifies several crystal parameters for the external crystal. Figure 4 shows a  
functional schematic of the oscillator circuit. The startup time is usually less than 1 second when using a crystal  
with the specified characteristics.  
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