DS1339 I2C Serial Real-Time Clock
PIN DESCRIPTION
PIN
ꢀSOP
NAME
FUNCTION
SO
Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator
circuitry is designed for operation with a crystal having a specified load
capacitance (CL) of 6pF. An external 32.768kHz oscillator can also drive the
DS1339. In this configuration, the X1 pin is connected to the external oscillator
signal and the X2 pin is floated.
For more information about crystal selection and crystal layout considerations,
refer to Application Note 58: Crystal Considerations with Dallas Real-Time
Clocks.
1
—
X1
X2
2
3
—
Secondary Power Supply. Supply voltage must be held between 1.3V and 3.7V
for proper operation. This pin can be connected to a primary cell, such as a
lithium button cell. Additionally, this pin can be connected to a rechargeable cell
or a super cap when used in conjunction with the trickle-charge feature. Diodes
should not be placed in series between the battery and the VBACKUP input, or
improper operation will result. UL recognized to ensure against reverse charging
current when used with a lithium battery If a back up supply is not required,
14
VBACKUP
VBACKUP must be grounded.
4
5
15
16
GND
SDA
Ground. DC power is provided to the device on these pins.
Serial Data Input/Output. SDA is the input/output pin for the I2C serial interface.
The SDA pin is an open-drain output and requires an external pullup resistor.
Serial Clock Input. SCL is used to synchronize data movement on the serial
6
7
1
2
SCL
interface.
Square-Wave/Interrupt Output. Programmable square-wave or interrupt output
signal. The SQW/INT pin is an open-drain output and requires an external pullup
resistor.
SQW/INT
8
3
VCC
Power Supply. DC power is provided to the device on these pins.
—
4–13
N.C.
No Connection. These pins are unused and must be connected to ground.
TYPICAL OPERATING CIRCUIT
VCC
VCC
CRYSTAL
RPU
RPU
VCC
CPU
1
2
8
VCC
X1
SCL
X2
6
5
7
3
SQW/INT
i
DS1339
SDA
VBACKUP
GND
4
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DALLAS [ DALLAS SEMICONDUCTOR ]
