DS1644-120 Maxim Integrated Products, DS1644-120 Datasheet - Page 4
![IC RAM TIMEKEEP NV 120NS 28-EDIP](/photos/6/58/65855/ds1225ab-200__sml.jpg)
DS1644-120
Manufacturer Part Number
DS1644-120
Description
IC RAM TIMEKEEP NV 120NS 28-EDIP
Manufacturer
Maxim Integrated Products
Type
Clock/Calendar/NVSRAMr
Datasheet
1.DS1644P-120.pdf
(14 pages)
Specifications of DS1644-120
Memory Size
256K (32K x 8)
Time Format
HH:MM:SS (24 hr)
Date Format
YY-MM-DD-dd
Interface
Parallel
Voltage - Supply
4.5 V ~ 5.5 V
Operating Temperature
0°C ~ 70°C
Mounting Type
Through Hole
Package / Case
28-DIP Module (600 mil), 28-EDIP
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Other names
DS1644120
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
DS1644-120
Manufacturer:
DALLAS
Quantity:
2 046
Part Number:
DS1644-120
Manufacturer:
DALLAS
Quantity:
20 000
Company:
Part Number:
DS1644-120+
Manufacturer:
Maxim
Quantity:
429
Part Number:
DS1644-120+
Manufacturer:
DALLAS
Quantity:
20 000
Company:
Part Number:
DS1644-120IND
Manufacturer:
DALLAS
Quantity:
6 100
Company:
Part Number:
DS1644-120IND
Manufacturer:
DALLAS
Quantity:
6 100
DS1644/DS1644P
SETTING THE CLOCK
The MSB Bit, (B7) of the control register is the write bit. Setting the write bit to a 1, like the read bit,
halts updates to the DS1644 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 0 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
bit is the MSB for the seconds registers. Setting it to
OSC
a 1 stops the oscillator.
FREQUENCY TEST BIT
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.,
low,
low, and address for seconds register remain valid and stable).
CE
OE
CLOCK ACCURACY (DIP MODULE)
The DS1644 is guaranteed to keep time accuracy to within 1 minute per month at 25C. The RTC is
calibrated at the factory by Dallas Semiconductor using nonvolatile tuning elements, and does not require
additional calibration. For this reason, methods of field clock calibration are not available and not
necessary. Clock accuracy is also affected by the electrical environment and caution should be taken to
place the RTC in the lowest level EMI section of the PCB layout. For additional information please see
application note 58.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1644 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. Clock
accuracy is also affected by the electrical environment and caution should be taken to place the RTC in
the lowest level EMI section of the PCB layout. For additional information please see application note
58.
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