21-0036 Просмотр технического описания (PDF) - Maxim Integrated
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21-0036 Datasheet PDF : 20 Pages
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DS1339 I2C Serial Real-Time Clock
PIN DESCRIPTION
PIN
µSOP SO
NAME
1
—
X1
2
—
X2
3
14
VBACKUP
4
15
5
16
6
1
GND
SDA
SCL
7
2
SQW/INT
8
3
— 4–13
VCC
N.C.
FUNCTION
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 left unconnected.
For more information about crystal selection and crystal layout considerations,
refer to Application Note 58: Crystal Considerations with Dallas Real-Time
Clocks.
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 backup source and the VBACKUP input,
or improper operation will result. If a backup supply is not required, VBACKUP must
be grounded. UL recognized to ensure against reverse charging current when
used with a lithium cell. For more information, visit www.maxim-ic.com/qa/info/ul.
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.
The pull up voltage may be up to 5.5V regardless of the voltage on VCC.
Serial Clock Input. SCL is used to synchronize data movement on the I2C serial
interface. The pull up voltage may be up to 5.5V regardless of the voltage on
VCC.
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. The pull up voltage may be up to 5.5V regardless of the voltage on VCC.
If not used, this pin may be left unconnected.
Primary Power Supply. When voltage is applied within normal limits, the device
is fully accessible and data can be written and read. When a backup supply is
connected and VCC is below VPF, reads and writes are inhibited. The timekeeping
and alarm functions operate when the device is powered by VCC or VBACKUP.
No Connection. These pins are unused and must be connected to ground.
TYPICAL OPERATING CIRCUIT
VCC
VCC
VCC RPU
RPU
CRYSTAL
1
2
8
6 X1 X2
SCL
VCC
7
SQW/INT
i
CPU
DS1339
5
SDA
3
VBACKUP
GND
4
8 of 20
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