参数资料
型号: DS1746W-120+
厂商: MAXIM INTEGRATED PRODUCTS INC
元件分类: XO, clock
英文描述: Y2K-Compliant, Nonvolatile Timekeeping RAMs
中文描述: REAL TIME CLOCK, PDIP32
封装: 0.740 INCH, ROHS COMPLIANT, EDIP-32
文件页数: 12/16页
文件大小: 140K
代理商: DS1746W-120+
DS1746/DS1746P Y2K-Compliant, Nonvolatile Timekeeping RAMs
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Table 1. Truth Table
VCC
CE
OE
WE
MODE
DQ
POWER
VIH
X
Deselect
High-Z
Standby
VIL
X
VIL
Write
Data In
Active
VIL
VIH
Read
Data Out
Active
VCC>VPF
VIL
VIH
Read
High-Z
Active
VSO<VCC<VPF
X
Deselect
High-Z
CMOS Standby
VCC<VSO<VPF
X
Deselect
High-Z
Data-Retention Mode
SETTING THE CLOCK
As shown in Table 2, bit 7 of the century register is the write bit. Setting the write bit to a one, like the
read bit, halts updates to the DS1746 registers. The user can then load them with the correct day, date and
time data in 24 hour BCD format. Resetting the write bit to a zero then transfers those values to the actual
clock counters and allows normal operation to resume.
STOPPING AND STARTING THE CLOCK OSCILLATOR
The clock oscillator may be stopped at any time. To increase the shelf life, the oscillator can be turned off
to minimize current drain from the battery. The
OSC bit is the MSB (bit 7) of the seconds registers (see
Table 2). Setting it to a one stops the oscillator.
FREQUENCY TEST BIT
As shown in Table 2, bit 6 of the day byte is the frequency test bit. When the frequency test bit is set to
logic “1” and the oscillator is running, the LSB of the seconds register will toggle at 512 Hz. When the
seconds register is being read, the DQ0 line will toggle at the 512 Hz frequency as long as conditions for
access remain valid (i.e.,
CE low, OE low, WE high, and address for seconds register remain valid and
stable).
CLOCK ACCURACY (DIP MODULE)
The DS1746 is guaranteed to keep time accuracy to within
1 minute per month at 25C. The RTC is
calibrated at the factory by Maxim using nonvolatile tuning elements, and does not require additional
calibration. For this reason, methods of field clock calibration are not available and not necessary. The
electrical environment also affects clock accuracy and caution should be taken to place the RTC in the
lowest-level EMI section of the PC board layout. For additional information, refer to Application Note
58.
CLOCK ACCURACY (PowerCap MODULE)
The DS1746 and DS9034PCX are each individually tested for accuracy. Once mounted together, the
module will typically keep time accuracy to within
1.53 minutes per month (35 ppm) at 25°C. The
electrical environment also affects clock accuracy and caution should be taken to place the RTC in the
lowest-level EMI section of the PC board layout. For additional information, refer to Application Note
58.
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