DS1682 Maxim, DS1682 Datasheet - Page 3

• Manufacturer Part Number: DS1682
• Description: The DS1682 is an integrated elapsed-time recorder containing a factory-calibrated, temperature-compensated RC time base that eliminates the need for an external crystal
• Manufacturer: Maxim

DS1682 Total-Elapsed-Time Recorder with Alarm
OPERATION
The block diagram in Figure 1 shows the relationship between the major functional blocks, the serial
interface, and the EEPROM memory section of the DS1682. Upon power-up, the DS1682 transfers the
contents of the EEPROM into the counters and memory registers where the data can be read and written
through the serial interface. The content of the counters and memory registers are written into the
EEPROM memory when the EVENT pin transitions from a logic high to a logic low.
The DS1682 uses a calibrated, temperature-compensated RC time base to increment an ETC while an
event is active. When the event becomes active, the contents of the nonvolatile EEPROM are transferred
to the ETC and event counter and the oscillator starts. As the event continues, the ETC is incremented in
quarter-second increments. When the event becomes inactive, the event counter is incremented and the
contents of the ETC and event counter are written to the nonvolatile EEPROM.
The ALARM output can be used to indicate when the ETC has matched the value in the alarm register.
The DS1682 can be configured to prevent clearing the alarm and the elapsed time and event counters.
The user memory can be separately write-protected.
User-modified data is not stored in EEPROM until an event becomes inactive.
Figure 2 shows the DS1682 measuring total run time and operating from a battery with the alarm tied to
an LED and a pushbutton switch to trigger the alarm output.
Figure 2. Total Run Time
Figure 3 shows the DS1682 in a total time-of-use application where power may be removed at the same
time as the end of the event. The V
slew rate at power-down is fast with respect to t
. A capacitor
CC
EW
maintains V
on the DS1682 above 2.5V until the EEPROM write completes. A Schottky diode blocks
CC
current from the capacitor to other devices connected to V
.
CC
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