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Low-Current SPI/3-Wire RTCs

19-5801; Rev 0; 3/11

General Description

The DS1343/DS1344 low-current real-time clocks (RTCs)

are timekeeping devices that provide an extremely low

standby current, permitting longer life from a backup

supply source. The devices also support high-ESR

crystals, broadening the pool of usable crystals for the

devices. 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 24-hour or

12-hour format with an AM/PM indicator.

Address and data are transferred serially through an

SPI™ or 3-wire interface. Two programmable time-of-day

alarms are provided. Each alarm can generate an inter-

rupt on a combination of seconds, minutes, hours, and

day. Don’t-care states can be inserted into one or more

fields if it is desired for them to be ignored for the alarm

condition. The time-of-day alarms can be programmed

to assert two different interrupt outputs, or they can be

combined to assert one common interrupt output. Both

interrupt outputs operate when the device is powered by

The devices are available in a lead-free/RoHS-compliant,

20-pin TSSOP or 14-pin TDFN package, and support a

-40°C to +85°C extended industrial temperature range.

Applications

Medical

Handheld Devices

Telematics

Embedded Timestamping

Features

S

Low Timekeeping Current of 250nA (typ)

S

Compatible with Crystal ESR Up to 100kI

S

Versions Available to Support Either 6pF or

12.5pF Crystals

S

RTC Counts Seconds, Minutes, Hours, Day, Date,

Month, and Year with Leap Year Compensation

Valid Through 2099

S

Power-Fail and Switch Circuitry

S

Three Operating Voltages

1.8V ±5%

3.0V±10%

3.3V ±10%

S

Trickle-Charge Capability

S

Maintain Time Down to 1.15V (typ)

S

Support Motorola SPI Modes 1 and 3, or Standard

3-Wire Interface

S

Burst Mode for Reading/Writing Successive

Addresses in Clock/RAM

S

96-Byte Battery-Backed NV RAM for Data Storage

S

Two Time-of-Day Alarms with Two Interrupt

Outputs

S

Industrial Temperature Range

S

20-Pin TSSOP or 14-Pin TDFN Package

Ordering Information appears at end of data sheet.

SPI is a trademark of Motorola, Inc.

Typical Operating Circuit

DS1343

DS1344

INT0

PF

INT1

CE

SCLK

SDI

SDO

X1

X2

GND

SERMODE

INT

RST

3-WIRE

PORT

P

NOTE: SHOWN IN 3-WIRE I/O CONFIGURATION.