
General Description
The DS1340 is a real-time clock (RTC)/calendar that is
pin compatible and functionally equivalent to the ST
M41T00, including the software clock calibration. The
device additionally provides trickle-charge capability
on the V
BACKUP
pin, a lower timekeeping voltage, and
an oscillator STOP flag. Block access of the register
map is identical to the ST device. Two additional regis-
ters, which are accessed individually, are required for
the trickle charger and flag. The clock/calendar pro-
vides seconds, minutes, hours, day, date, month, and
year information. A built-in power-sense circuit detects
power failures and automatically switches to the back-
up supply. The device is programmed serially through
an I
2
C
TM
bidirectional bus.
Applications
Portable Instruments
Point-of-Sale Equipment
Medical Equipment
Telecommunications
Features
Enhanced Second Source for the ST M41T00
Available in a Surface-Mount Package with an
Integrated Crystal (DS1340C)
Fast (400kHz) I
2
C Interface
Software Clock Calibration
RTC Counts Seconds, Minutes, Hours, Day, Date,
Month, and Year
Automatic Power-Fail Detect and Switch Circuitry
Trickle-Charge Capability
Low Timekeeping Voltage Down to 1.3V
Three Operating Voltage Ranges (1.8V, 3V, and 3.3V)
Oscillator Stop Flag
Available in 8-Pin μSOP or SO Packages
Underwriters Laboratory (UL) Recognized
Ordering Information
D
I
2
C RTC with Trickle Charger
______________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
4
CPU
V
CC
V
CC
V
CC
FT/OUT
5
6
8
1
2
SDA
SCL
GND
X2
X1
V
CC
RPU
RPU
CRYSTAL
V
BACKUP
3
7
RPU = t
R
/ C
B
DS1340
Typical Operating Circuit
Rev 2; 12/04
PART
TEMP RANGE
PIN-PACKAGE
TOP
MARK
D1340-18
DS1340-3
D1340-33
1340
A1-18
1340
A1-3
1340
A1-33
1340C-18
1340C-3
1340C-33
D1340-18
DS1340-3
D1340-33
1340
A1-18
1340
A1-3
1340
A1-33
1340C-18
1340C-3
1340C-33
DS1340Z-18
DS1340Z-3
DS1340Z-33
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
8 SO (0.150in)
8 SO (0.150in)
8 SO (0.150in)
DS1340U-18
-40°C to +85°C
8 μSOP
DS1340U-3
-40°C to +85°C
8 μSOP
DS1340U-33
-40°C to +85°C
8 μSOP
DS1340C-18
DS1340C-3
DS1340C-33
DS1340Z-18+
DS1340Z-3+
DS1340Z-33+
-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
16 SO
16 SO
16 SO
8 SO (0.150in)
8 SO (0.150in)
8 SO (0.150in)
DS1340U-18+
-40°C to +85°C
8 μSOP
DS1340U-3+
-40°C to +85°C
8 μSOP
DS1340U-33+
-40°C to +85°C
8 μSOP
DS1340C-18+
DS1340C-3+
DS1340C-33+
Note: A "+" in the part number and a "+" anywhere on the top
mark indicates a lead-free device.
Pin Configurations appear at end of data sheet.
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
16 SO
16 SO
16 SO
I
2
C is a trademark of Philips Corp. Purchase of I
2
C compo-
nents from Maxim Integrated Products, Inc., or one of its subli-
censed Associated Companies, conveys a license under the
Philips I
2
C Patent Rights to use these components in an I
2
C
system, provided that the system conforms to the I
2
C Standard
Specification as defined by Philips.