Datasheet

DS1683
Total-Elapsed-Time and Event Recorder with Alarm
16Maxim Integrated
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, I
2
C write
commands are disabled, thus only I
2
C read commands
are possible in these configurations.
Figure 4. Total Run Time
Figure 5. Total Time-of-Use Application with Fast V
CC
Slew
Rate (Read-Only)
Figure 6. Total Time-of-Use Application with Slow V
CC
Slew
Rate (Read-Only)
DS1683
V
CC
EVENT
TRIGGER SWITCH
LED
SCLALARM
SDAGND
0.01µF
DS1683
V
CC
EVENT
LED
SCLALARM
SDAGND
0.01µF 30µF
V
CC
DS1683
V
CC
ALARM
LED
SCLEVENT
SDAGND
0.01µF
V
CC
V
CC
RESET
IC