DS1647-120 Maxim Integrated Products, DS1647-120 Datasheet - Page 3
![no-image](/images/manufacturer_photos/0/4/417/maxim_integrated_products_sml.jpg)
DS1647-120
Manufacturer Part Number
DS1647-120
Description
Real Time Clock
Manufacturer
Maxim Integrated Products
Datasheet
1.DS1647-120.pdf
(12 pages)
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
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
DS1647-120+
Manufacturer:
TI
Quantity:
209
DS1647/DS1647P
DESCRIPTION
The DS1647 is a 512k x 8 nonvolatile static RAM with a full-function real-time clock, which are both
accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to any
JEDEC standard 512k x 8 SRAM. The device can also be easily substituted for ROM, EPROM and
EEPROM, providing read/write nonvolatility and the addition of the real-time clock function. The real-
time clock information resides in the eight uppermost RAM locations. The RTC registers contain year,
month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the day of the
month and leap year are made automatically. The RTC clock registers are double-buffered to avoid access
of incorrect data that can occur during clock update cycles. The double-buffered system also prevents
time loss as the timekeeping countdown continues unabated by access to time register data. The DS1647
also contains its own power-fail circuitry, which deselects the device when the V
supply is in an out-of-
CC
tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by
low V
as errant access and update cycles are avoided.
CC
PACKAGES
The DS1647 is available in two packages: 32-pin DIP and 34-pin PowerCap module. The 32-pin DIP
style module integrates the crystal, lithium energy source, and silicon all in one package. The 34-pin
PowerCap Module Board is designed with contacts for connection to a separate PowerCap (DS9034PCX)
that contains the crystal and battery. This design allows the PowerCap to be mounted on top of the
DS1647P after the completion of the surface mount process. Mounting the PowerCap after the surface
mount process prevents damage to the crystal and battery due to the high temperatures required for solder
reflow. The PowerCap is keyed to prevent reverse insertion. The PowerCap Module Board and PowerCap
are ordered separately and shipped in separate containers. The part number for the PowerCap is
DS9034PCX.
CLOCK OPERATIONS—READING THE CLOCK
While the double-buffered register structure reduces the chance of reading incorrect data, internal updates
to the DS1647 clock registers should be halted before clock data is read to prevent reading of data in
transition. However, halting the internal clock register updating process does not affect clock accuracy.
Updating is halted when a 1 is written into the read bit, the 7th most significant bit in the control register.
As long as 1 remains in that position, updating is halted. After a halt is issued, the registers reflect the
count, that is day, date, and time that was present at the moment the halt command was issued. However,
the internal clock registers of the double-buffered system continue to update so that clock accuracy is not
affected by the access of data. All of the DS1647 registers are updated simultaneously after the clock
status is reset. Updating is within a second after the read bit is written to 0.
The read bit must be a zero for a minimum of 500µs to ensure that the external registers are updated.
3 of 12