DS1678 Datasheet, PDF (6/25 Pages) Maxim Integrated Products – Real-Time Event Recorder

DS1678 Real-Time Event Recorder
PIN DESCRIPTION
PIN
NAME
FUNCTION
Connections for Standard 32.768kHz Quartz Crystal. For greatest accuracy,
the DS1678 must be used with a crystal that has a specified load capacitance
of 12.5pF. There is no need for external capacitors or resistors. Note: X1 and
1, 2
X1, X2 X2 are very high-impedance nodes. It is recommended that they and the
crystal be isolated from high-frequency signals. For more information on
crystal selection and crystal layout considerations, refer to Application Note
58: Crystal Considerations with Dallas Real-Time Clocks.
Battery Input for Standard Lithium Cell or Other Energy Source. All
functions of the DS1678 with the exception of the serial interface circuitry
are powered by V_BAT when V_CC < V_BAT. All functions are powered by V_CC
when V_CC > V_BAT. The serial interface is enabled when V_CC is above V_PF. If
3
V_BAT a battery or other energy source is not used, V_BAT should be connected
directly to ground. Diodes must not be placed between the battery and the
V_BAT input or improper operation results. UL recognized to ensure against
reverse charging current when used with a lithium battery. See “Conditions
of Acceptability” at www.maxim-ic.com/qa/info/ul/.
4
GND Ground
Serial Data Input/Output. SDA is the data input/output (I/O) signal for the
5
SDA I²C serial interface. The SDA pin is an open-drain I/O and requires an
external pullup resistor.
6
SCL
Serial Clock Input. SCL is used to synchronize data movement on the serial
interface. It requires an external pullup resistor.
Active-Low Interrupt Input/Output. The INT pin is an I/O that is activated by
an external device to signify an event has occurred and should be logged.
Once the pin is activated, the event is recorded in the event-log memory and
the Event Counter Register is incremented. The TRx bits determine which
input edge(s) trigger an event: An event can be triggered by a falling edge on
the INT pin, a rising edge, or by both the rising and falling edges.
7
INT The INT pin can also be used as an output when the DS1678 is not in an
event-logging mission. The INT pin becomes an output and generates an
alarm interrupt if the DISx bits are set to zero and the RTC reaches the preset
value in the alarm register. The INT output remains low as long as the status
bit causing the interrupt is present and the DISx bits are set to zero.
The INT pin is an open-drain input/output with a weak internal pulldown
resistor to prevent the pin from floating when the pin is tri-stated.
8
V_CC DC Power for Primary Power Supply
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