6

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Detailed Description

The DS1340 is a low-power clock/calendar with a trickle

charger. Address and data are transferred serially

vides 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 DS1340

has a built-in power-sense circuit that detects power fail-

ures and automatically switches to the backup supply.

Power Control

The power-control function is provided by a precise,

temperature-compensated voltage reference and a

device is fully accessible and data can be written and

Pin Description

PIN

816

NAME

FUNCTION

1

—

X1

2

—

X2

Connections for a Standard 32.768kHz Quartz Crystal. The internal oscillator circuitry is designed for

oscillator and can optionally be connected to an external 32.768kHz oscillator. The output of the

internal oscillator, X2, is left unconnected if an external oscillator is connected to X1.

3

14

between 1.3V and 3.7V for proper operation. Diodes placed in series between the supply and the input

This pin can be connected to a primary cell such as a lithium coin cell. Additionally, this pin can be

connected to a rechargeable cell or a super cap when used with the trickle-charge feature. UL recognized to

ensure against reverse charging when used with a lithium battery (www.maxim-ic.com/qa/info/ul).

4

15

GND

Ground

5

16

SDA

Serial Data Input/Output. SDA is the data input/output for the I

drain and requires an external pullup resistor.

6

1

SCL

Serial Clock Input. SCL is the clock input for the I

movement on the serial interface.

7

2

FT/OUT

Frequency Test/Output. This pin is used to output either a 512Hz signal or the value of the OUT bit.

When the FT bit is logic 1, the FT/OUT pin toggles at a 512Hz rate. When the FT bit is logic 0, the

FT/OUT pin reflects the value of the OUT bit. This open-drain pin requires an external pullup resistor,

8

3

Primary Power Supply. When voltage is applied within normal limits, the device is fully accessible and

reads and writes are inhibited. However, the timekeeping function continues unaffected by the lower

input voltage.

—

4–13

N.C.

No Connection. Must be connected to ground.

SUPPLY CONDITION

READ/WRITE

ACCESS

POWERED

BY

No

No

Yes

Yes

Table 1. Power Control