Rev 2; 12/04
I2C RTC with Trickle Charger
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 VBACKUP 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 I2CTM bidirectional bus.
Portable Instruments
Point-of-Sale Equipment
Medical Equipment
Telecommunications
Applications
Typical Operating Circuit
VCC RPU
VCC
CRYSTAL
RPU
1
2
X1 X2
6 SCL
VCC
8
VCC
7
FT/OUT
CPU
RPU = tR / CB
5 SDA
DS1340
3
VBACKUP
GND
4
I2C is a trademark of Philips Corp. Purchase of I2C compo-
nents from Maxim Integrated Products, Inc., or one of its subli-
censed Associated Companies, conveys a license under the
Philips I2C Patent Rights to use these components in an I2C
system, provided that the system conforms to the I2C Standard
Specification as defined by Philips.
Features
♦ Enhanced Second Source for the ST M41T00
♦ Available in a Surface-Mount Package with an
Integrated Crystal (DS1340C)
♦ Fast (400kHz) I2C 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
PART
TEMP RANGE
PIN-PACKAGE
TOP
MARK
DS1340Z-18 -40°C to +85°C 8 SO (0.150in) D1340-18
DS1340Z-3 -40°C to +85°C 8 SO (0.150in) DS1340-3
DS1340Z-33 -40°C to +85°C 8 SO (0.150in) D1340-33
DS1340U-18 -40°C to +85°C 8 µSOP
DS1340U-3 -40°C to +85°C 8 µSOP
1340
A1-18
1340
A1-3
DS1340U-33 -40°C to +85°C 8 µSOP
1340
A1-33
DS1340C-18 -40°C to +85°C 16 SO
1340C-18
DS1340C-3 -40°C to +85°C 16 SO
1340C-3
DS1340C-33 -40°C to +85°C 16 SO
1340C-33
DS1340Z-18+ -40°C to +85°C 8 SO (0.150in) D1340-18
DS1340Z-3+ -40°C to +85°C 8 SO (0.150in) DS1340-3
DS1340Z-33+ -40°C to +85°C 8 SO (0.150in) D1340-33
DS1340U-18+ -40°C to +85°C 8 µSOP
1340
A1-18
DS1340U-3+ -40°C to +85°C 8 µSOP
1340
A1-3
DS1340U-33+ -40°C to +85°C 8 µSOP
1340
A1-33
DS1340C-18+ -40°C to +85°C 16 SO
1340C-18
DS1340C-3+ -40°C to +85°C 16 SO
1340C-3
DS1340C-33+ -40°C to +85°C 16 SO
1340C-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.
______________________________________________ Maxim Integrated Products 1
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.