DS1744W-120 Maxim Integrated Products, DS1744W-120 Datasheet - Page 7

• Manufacturer Part Number: DS1744W-120
• Description: IC RTC RAM Y2K 3.3V 120NS 28EDIP
• Manufacturer: Maxim Integrated Products
• Type: Clock/Calendar/NVSRAM/Y2Kr

Specifications of DS1744W-120

• Memory Size: 256K (32K x 8)
• Time Format: HH:MM:SS (24 hr)
• Date Format: YY-MM-DD-dd
• Interface: Parallel
• Voltage - Supply: 3 V ~ 3.6 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

DATA-RETENTION MODE
The 5V device is fully accessible and data can be written or read only when V
However, when V
internal clock registers and SRAM are blocked from any access. At this time the power-fail reset-output
signal ( RST ) is driven active and remains active until V
below the battery switch point V
backup battery. RTC operation and SRAM data are maintained from the battery until V
nominal levels. The 3.3V device is fully accessible, and data can be written or read only when V
greater than V
reset-output signal ( RST ) is driven active and remains active until V
less than V
V
V
returned to nominal levels. The RST signal is an open-drain output and requires a pullup. Except for the
BATTERY LONGEVITY
The DS1744 has a lithium power source that is designed to provide energy for clock activity and clock and
RAM data retention when the V
sufficient to power the DS1744 continuously for the life of the equipment in which it is installed. For
specification purposes, the life expectancy is 10 years at +25C with the internal clock oscillator running
in the absence of V
disconnected, guaranteeing full energy capacity. When V
lithium energy source is enabled for battery-backup operation. Actual life expectancy of the DS1744 is
much longer than 10 years since no lithium battery energy is consumed when V
BATTERY MONITOR
The DS1744 constantly monitors the battery voltage of the internal battery. The battery flag bit (bit 7) of
the day register is used to indicate the voltage-level range of the battery. This bit is not writable and should
always be a 1 when read. If a 0 is ever present, an exhausted lithium energy source is indicated, and both
the contents of the RTC and RAM are questionable.
RST , all control, data, and address signals must be powered down when V
PF
CC
.
If V
drops below V
PF
SO
is greater than V
, the device power is switched from V
PF
.
When V
CC
SO
CC
is below the power-fail point, V
. RTC operation and SRAM data are maintained from the battery until V
power. Each DS1744 is shipped from Maxim with its lithium energy source
CC
SO
falls below V
, the device power is switched from V
SO
CC
(battery supply level), device power is switched from the V
supply is not present. The capability of this internal power supply is
PF
DS1744/DS1744P Y2K-Compliant, Nonvolatile Timekeeping RAMs
access to the device is inhibited. At this time the power-fail
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CC
to the backup supply (V
PF
CC
CC
(point at which write protection occurs), the
is first applied at a level greater than V
returns to nominal levels. When V
CC
CC
to the backup supply (V
returns to nominal levels. If V
CC
is powered down.
BAT
CC
) when V
is present.
CC
is greater than V
CC
CC
is returned to
CC
drops below
BAT
pin to the
CC
) when
PF
CC
CC
, the
falls
PF
PF
is
is
is
.