DS1683_12 Datasheet, PDF (16/21 Pages) Maxim Integrated Products – Total-Elapsed-Time and Event Recorder with Alarm

DS1683
Total-Elapsed-Time and Event Recorder with Alarm
Sample Applications
Figure 4 shows the DS1683 measuring total run time and
operating from a battery with the ALARM pin connected
to an LED. When the trigger switch is closed, the EVENT
pin is pulled high and the ETC register begins increment-
ing. When the trigger switch is opened, the EVENT pin is
pulled low by the resistor, the ETC register stops incre-
menting, the Event Counter register is incremented by
one, and the values of both the ETC and Event Counter
are stored in shadowed EEPROM. When the ETC or
Event Counter alarm conditions are met, the ALARM pin
pulls active low (the factory default setting), and current
flows through the LED, indicating an alarm condition.
Figure 5 shows the DS1683 in a total time-of-use applica-
tion where power may be removed at the same time as
the end of the event. The V_CC slew rate at power-down is
fast with respect to t_W. A capacitor maintains V_CC on the
DS1683 above 2.5V until the EEPROM write completes. A
Schottky diode blocks current from the capacitor to other
devices connected to V_CC.
The V_CC holding capacitor value of 30FF is calculated
using the maximum EEPROM write current and EEPROM
write time. This assumes that the V_CC slew rate allows
time from EVENT trip point to V_CC at 2.5V on the DS1683
is at least t_W.
Figure 6 shows the DS1683 in a total time-of-use applica-
tion with power that can be removed at the same time as
the end of the event. In this application, the V_CC slew rate
at power-down is slow with respect to t_W. The external
RST IC ends the event as V_CC begins to drop. V_CC must
remain above 2.5V until the end of t_W.
Both circuits in Figure 5 and Figure 6 are read-only
because the state of the EVENT pin is tied V_CC. Because
the EVENT pin is a logic 1 while V_CC is applied, I²C write
commands are disabled, thus only I²C read commands
are possible in these configurations.
TRIGGER SWITCH
EVENT
VCC
LED
DS1683
0.01µF
ALARM
SCL
GND
SDA
Figure 4. Total Run Time
EVENT
V_CC
LED
DS1683
ALARM
SCL
GND
SDA
VCC
0.01µF
30µF
Figure 5. Total Time-of-Use Application with Fast V_CC Slew
Rate (Read-Only)
VCC
VCC
RESET
IC
LED
ALARM
VCC
DS1683
EVENT
SCL
GND
SDA
0.01µF
Figure 6. Total Time-of-Use Application with Slow V_CC Slew
Rate (Read-Only)
Maxim Integrated
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