DS1341_10 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – Low-Current I2C RTCs for High-ESR Crystals

19-4998; Rev 1; 12/10
Low-Current I²C RTCs for High-ESR Crystals
General Description
The DS1341/DS1342 low-current real-time clocks (RTCs)
are timekeeping devices that provide an extremely low
standby current, which permits longer life from a power
supply. The DS1341/DS1342 support high-ESR crystals,
which broaden the pool of usable crystals for the devices.
The DS1341 uses a 6pF crystal, while the DS1342 uses a
12.5pF crystal. These devices are accessed through an
I²C serial interface. Other features include two time-of-day
alarms, two interrupt outputs, a programmable square-
wave output, and a serial bus timeout mechanism.
The clock/calendar provides seconds, minutes, hours,
day, date, month, and year information. The date at the
end of the month is automatically adjusted for months
with fewer than 31 days, including corrections for leap
year. The clock operates in either 24hr or 12hr format
with an AM/PM indicator.
The DS1341/DS1342 also include an input for synchroni-
zation. When a reference clock (e.g., 60Hz power line or
GPS 1PPS) is present at the CLKIN pin and the enable
external clock input bit (ECLK) is set to 1, the DS1341/
DS1342 RTCs are frequency-locked to the external clock
and the clock accuracy is determined by the external
source. In case of external clock failure, the clock is
switched to the crystal oscillator.
The devices are available in lead(Pb)-free/RoHS-
compliant, 8-pin FSOP or TDFN packages. The devices
support a -40NC to +85NC extended temperature range.
Ordering Information
PART
DS1341U+
DS1341U+T&R
TEMP RANGE
-40NC to +85NC
-40NC to +85NC
PIN-
PACKAGE
8 FSOP
8 FSOP
OSC
CL (pF)
6
6
DS1341T+*
-40NC to +85NC 8 TDFN-EP**
6
DS1341T+T&R* -40NC to +85NC 8 TDFN-EP**
6
DS1342U+
-40NC to +85NC 8 FSOP
12.5
DS1342U+T&R -40NC to +85NC 8 FSOP
12.5
DS1342T+*
-40NC to +85NC 8 TDFN-EP** 12.5
DS1342T+T&R* -40NC to +85NC 8 TDFN-EP** 12.5
+Denotes a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
*Future product—contact factory for availability.
**EP = Exposed pad.
Features
S Low Timekeeping Current of 250nA (typ)
S Compatible with Crystal ESR Up to 100kI
S Use Crystals with CL = 6pF (DS1341) or
CL = 12.5pF (DS1342)
S +1.8V to +5.5V Operating Voltage Range
S Maintain Time Down to +1.15V (typ)
S Fast (400kHz) I²C Interface
S Bus Timeout for Lockup-Free Operation
S RTC Counts Seconds, Minutes, Hours, Day, Date,
Month, and Year with Leap Year Compensation
Valid Through 2099
S External Clock Source for Synchronization Clock
Reference (e.g., 32kHz, 50Hz/60Hz Power Line,
GPS 1PPS)
S Two Time-of-Day Alarms with Two Interrupt
Outputs
S Programmable Square-Wave Output
S Industrial Temperature Range
S Small, 8-Pin µSOP or TDFN Packages
Medical
Point of Sale (POS)
Telematics
Applications
Portable Instruments
Portable Audio
Automotive
Typical Operating Circuit
VCC
VCC
RPU RPU RPU
CPU
SCL ^VCC X1
SDA
CLKIN/INTA
SQW/INTB
X2
DS1341/DS1342
GND
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