Datasheet

DS1747/DS1747P Y2K-Compliant, Nonvolatile Timekeeping RAMs
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ORDERING INFORMATION
PART
SUPPLY
VOLTAGE
(V)
TEMP RANGE PIN-PACKAGE
TOP MARK
†
DS1747-70+
5.0
0°C to +70°C
32 EDIP (0.740a)
DS1747-70+
DS1747-70IND+
5.0
-40°C to +85°C
32 EDIP (0.740a)
DS1747-70IND+
DS1747P-70+
5.0
0°C to +70°C
34 PowerCap*
DS1747P+70
DS1747P-70IND+
5.0
-40°C to +85°C
34 PowerCap*
DS1747P+70 IND
DS1747W-120+
3.3
0°C to +70°C
32 EDIP (0.740a)
DS1747W-120+
DS1747W-120IND+
3.3
-40°C to +85°C
32 EDIP (0.740a)
DS1747W-120IND+
DS1747WP-120+
3.3
0°C to +70°C
34 PowerCap*
DS1747WP+120
DS1747WP-120IND+
3.3
-40°C to +85°C
34 PowerCap*
DS1747WP+120 IND
+Denotes a lead(Pb)-free/RoHS-compliant package.
*DS9034PCX+ or DS9034I-PCX+ required (must be ordered separately).
†A “+” indicates lead(Pb)-free. The top mark will include a “+” symbol on lead(Pb)-free devices.
DESCRIPTION
The DS1747 is a full-function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) and
512k x 8 nonvolatile static RAM. User access to all registers within the DS1747 is accomplished with a
byte-wide interface as shown in Figure 1. The RTC information and control bits reside in the eight
uppermost RAM locations. The RTC registers contain century, year, month, date, day, hours, minutes,
and seconds data in 24-hour binary-coded decimal (BCD) format. Corrections for the date of each 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 DS1747 also
contains its own power-fail circuitry that deselects the device when the V
CC
supply is in an out-of-
tolerance condition. This feature prevents loss of data from unpredictable system operation brought on
by low V
CC
as errant access and update cycles are avoided.