2
I C RTC with Trickle Charger
DS1340
General Description
Benefits and Features
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
• Enhanced Second Source for the ST M41T00
• Completely Manages All Timekeeping Functions
• RTC Counts Seconds, Minutes, Hours, Day, Date,
Month, and Year
on the V
pin, a lower timekeeping voltage, and
BACKUP
• Software Clock Calibration
• Oscillator Stop Flag
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. Reads and writes are inhibited while the
clock continues to run. The device is programmed seri-
• Low-Power Operation Extends Battery Backup Run
Time
• Low Timekeeping Voltage Down to 1.3V
• Automatic Power-Fail Detect and Switch Circuitry
• Trickle-Charge Capability
• Three Operating Voltage Ranges (1.8V, 3V, and 3.3V)
Supports Systems Using Legacy and Modern Power
Buses
2
ally through an I C bidirectional bus.
• Surface-Mount Package with an Integrated Crystal
(DS1340C) Saves Additional Space and Simplifies
Design
Applications
Portable Instruments
Point-of-Sale Equipment
Medical Equipment
Telecommunications
• Simple Serial Port Interfaces with Most Microcontrollers
2
• Fast (400kHz) I C Interface
• 8-Pin µSOP or SO Package Minimizes Required
Space
®
• Underwriters Laboratories (UL ) Recognized
Ordering Information
Typical Operating Circuit
PIN-
†
PART
TEMP RANGE
TOP MARK
D1340-18
DS1340-3
D134033
PACKAGE
8 SO
(0.150in)
V
V
CC
CC
DS1340Z-18+ -40°C to +85°C
CRYSTAL
8 SO
(0.150in)
V
CC
DS1340Z-3+
-40°C to +85°C
C1
R
R
PU
PU
1
2
8
X1
X2
V
CC
8 SO
(0.150in)
7
3
DS1340Z-33+ -40°C to +85°C
6
5
SCL
FT/OUT
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# -40°C to +85°C 16 SO
1340 -18
CPU
DS1340
1340 -3
SDA
V
1340 -33
BACKUP
GND
4
DS1340C-18
DS1340C-3
DS1340C-33
R
= t / C
R B
PU
DS1340C-3#
-40°C to +85°C 16 SO
DS1340C-33# -40°C to +85°C 16 SO
+Denotes a lead(Pb)-free/RoHS-compliant package.
#Denotes a RoHS-compliant device that may include lead(Pb)
that is exempt under RoHS requirements. The lead finish is
JESD97 category e3, and is compatible with both lead-based
and lead-free soldering processes.
Pin Configurations appear at end of data sheet.
†A "+" anywhere on the top mark denotes a lead(Pb)-free device.
A "#" denotes a RoHS-compliant device.
UL is a registered trademark of Underwriters Laboratories Inc.
19-5578; Rev 9; 4/15