DS1683STR datasheet(16/21 Pages) MAXIM

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DS1683

Total-Elapsed-Time and Event Recorder with Alarm

Maxim 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 VCC slew rate at power-down is

fast with respect to tW. A capacitor maintains VCC on the

DS1683 above 2.5V until the EEPROM write completes. A

Schottky diode blocks current from the capacitor to other

devices connected to VCC.

The VCC holding capacitor value of 30FF is calculated

using the maximum EEPROM write current and EEPROM

write time. This assumes that the VCC slew rate allows

time from EVENT trip point to VCC at 2.5V on the DS1683

is at least tW.

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 VCC slew rate

at power-down is slow with respect to tW. The external

RST IC ends the event as VCC begins to drop. VCC must

remain above 2.5V until the end of tW.

Both circuits in Figure 5 and Figure 6 are read-only

because the state of the EVENT pin is tied VCC. Because

the EVENT pin is a logic 1 while VCC is applied, I2C write

commands are disabled, thus only I2C read commands

are possible in these configurations.

Figure 4. Total Run Time

Figure 5. Total Time-of-Use Application with Fast VCC Slew

Rate (Read-Only)

Figure 6. Total Time-of-Use Application with Slow VCC Slew

Rate (Read-Only)

DS1683

VCC

EVENT

TRIGGER SWITCH

LED

SCL

ALARM

SDA

GND

0.01µF

DS1683

VCC

EVENT

LED

SCL

ALARM

SDA

GND

0.01µF

30µF

VCC

DS1683

VCC

ALARM

LED

SCL

EVENT

SDA

GND

0.01µF

VCC

RESET

DS1683STR Datasheet(PDF) 16 Page - Maxim Integrated Products

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