19-6019; Rev 3/12
DS1338
I
2
C RTC with 56-Byte NV RAM
GENERAL DESCRIPTION
The DS1338 serial real-time clock (RTC) is a low-
power, full binary-coded decimal (BCD)
clock/calendar plus 56 bytes of NV SRAM. Address
2
and data are transferred serially through an I C
interface. The clock/calendar provides seconds,
minutes, hours, day, date, month, and year
information. The end of the month date is
automatically adjusted for months with fewer than 31
days, including corrections for leap year. The clock
operates in either the 24-hour or 12-hour format with
AM/PM indicator. The DS1338 has a built-in power-
sense circuit that detects power failures and
automatically switches to the backup supply,
maintaining time and date operation
FEATURES
RTC Counts Seconds, Minutes, Hours, Date
of the Month, Month, Day of the Week, and
Year with Leap-Year Compensation Valid Up
to 2100
Available in a Surface-Mount Package with an
Integrated Crystal (DS1338C)
56-Byte Battery-Backed General-Purpose
RAM with Unlimited Writes
2
I C Serial Interface
Programmable Square-Wave Output Signal
Automatic Power-Fail Detect and Switch
Circuitry
-40°C to +85°C Operating Temperature Range
Underwriters Laboratories (UL) Recognized
APPLICATIONS
Handhelds (GPS, POS Terminal)
Consumer Electronics (Set-Top Box, Digital
Recording, Network Appliance)
Office Equipment (Fax/Printer, Copier)
Medical (Glucometer, Medicine Dispenser)
Telecommunications (Router, Switcher, Server)
Other (Utility Meter, Vending Machine, Thermostat,
Modem)
ORDERING INFORMATION
PART
DS1338Z-18+
DS1338Z-3+
DS1338Z-33+
DS1338U-18+
DS1338U-3+
DS1338U-33+
DS1338C-18#
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 SO (0.150″)
8 SO (0.150″)
8 SO (0.150″)
8
µSOP
8
µSOP
8
µSOP
16 SO (0.300″)
TOP MARK†
DS1338-18
DS1338-3
DS133833
1338
rr-18
1338
rr-3
1338
rr-33
DS1338C-18
TYPICAL OPERATING CIRCUIT
R
PU
= t
r
/C
b
V
CC
R
PU
CRYSTAL
V
CC
V
CC
R
PU
X1
SCL
CPU
SDA
X2
V
CC
SQW/OUT
V
BAT
i
DS1338
GND
DS1338C-3#
-40°C to +85°C
DS1338C-3
16 SO (0.300″)
DS1338C-33#
-40°C to +85°C
16 SO (0.300″)
DS1338C-33
rr = second line, revision level
+ Denotes a lead(Pb)-free/RoHS-compliant device.
# Denotes a RoHS-compliant device that may include lead that is
exempt under the RoHS requirements. The lead finish is JESD97
category e3, and is compatible with both lead-based and lead-free
soldering processes.
†
A “+” anywhere on the top mark denotes a lead-free device. A “#”
denotes a RoHS-compliant device.
Pin Configurations appear at end of data sheet.
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