DS1647-120 Maxim Integrated Products, DS1647-120 Datasheet - Page 5

• Manufacturer Part Number: DS1647-120
• Description: Real Time Clock
• Manufacturer: Maxim Integrated Products

Specifications of DS1647-120

• Function: Clock, Calendar, NV Timekeeping RAM
• Rtc Memory Size: 524288 B
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 4.5 V
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: Through Hole
• Rtc Bus Interface: Parallel
• Package / Case: eDIP
• Time Format: HH:MM:SS
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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 DS1647 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 OSC bit is the MSB for the second’s registers. Setting it
to 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 second’s register will toggle at 512Hz. When the seconds register is
being read, the DQ0 line will toggle at the 512Hz frequency as long as conditions for access remain valid
(i.e., CE low, OE low, and address for seconds register remain valid and stable).
CLOCK ACCURACY (DIP MODULE)
The DS1647 is guaranteed to keep time accuracy to within ±1 minute per month at +25°C. 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 PC board layout. For additional information, refer
to Application Note 58.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1647 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 (35ppm) 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 PC board layout. For additional information, refer to Application
Note 58.
Table 2. Register Map—BANK1
OSC = STOP BIT
W = WRITE BIT
Note:
ADDRESS
7FFFE
7FFFD
7FFFC
7FFFB
7FFFA
7FFFF
7FFF9
7FFF8
All indicated “X” bits are unused, but must be set to “0” when written to ensure proper clock operation.
OSC
B
—
W
X
X
X
X
X
7
R = READ BIT
X = UNUSED
FT
B
—
—
—
X
X
X
R
6
B
—
—
—
—
—
X
X
X
5
FT = FREQUENCY TEST
B
—
—
—
—
—
—
X
X
4
DATA
B
—
—
—
—
—
—
5 of 12
X
X
3
B
—
—
—
—
—
—
—
X
2
B
—
—
—
—
—
—
—
X
1
B
—
—
—
—
—
—
—
X
0
Seconds
Minutes
Control
Month
Hour
Year
Date
Day
FUNCTION
DS1647/DS1647P
00–99
01–12
01–31
01–07
00–23
00–59
00–59
A