adm697ar-reel Analog Devices, Inc., adm697ar-reel Datasheet - Page 6

• Manufacturer Part Number: adm697ar-reel
• Description: ?p Supervisor With Backup Battery Switchover, Adjustable Low Line Voltage Monitor, Adjustable Watchdog Timer, Low Line, Power Fail And Watchdog Status Outputs And 100ma Output Current
• Manufacturer: Analog Devices, Inc.

OSC SEL
Low
Low
Floating or High
Floating or High
NOTE
With the OSC SEL pin low, OSC IN can be driven by an external clock signal, or an external capacitor can be connected between OSC IN and GND. The nominal
internal oscillator frequency is 10.24 kHz. The nominal oscillator frequency with external capacitor is: F
ADM696/ADM697
The watchdog timeout period defaults to 1.6 s and the reset
pulse width defaults to 50 ms but these times to be adjusted as
shown in Table I. Figure 4 shows the various oscillator configu-
rations which can be used to adjust the reset pulse width and
watchdog timeout period.
The internal oscillator is enabled when OSC SEL is high or
floating. In this mode, OSC IN selects between the 1.6 second
and 100 ms watchdog timeout periods. In either case, immedi-
ately after a reset the timeout period is 1.6 s. This gives the mi-
croprocessor time to reinitialize the system. If OSC IN is low,
then the 100 ms watchdog period becomes effective after the
first transition of WDI. The software should be written such
that the I/O port driving WDI is left in its power-up reset state
until the initialization routines are completed and the micropro-
cessor is able to toggle WDI at the minimum watchdog timeout
period of 70 ms.
Figure 3. Watchdog Timeout Period and Reset Active Time
RESET
WDO
WDI
t
t
t
1
2
3
= WATCHDOG TIMEOUT PERIOD IMMEDIATELY FOLLOWING A RESET
= RESET TIME
= NORMAL (SHORT) WATCHDOG TIMEOUT PERIOD
0 TO 250kHz
t
Figure 4a. External Clock Source
1
CLOCK
t
OSC IN
External Clock Input
External Capacitor
Low
Floating or High
2
Table I. ADM696, ADM697 Reset Pulse Width and Watchdog Timeout Selections
8
7
OSC IN
OSC SEL
t
1
ADM69x
t
3
t
1
Normal
1024 CLKS
400 ms
100 ms
1.6 s
C/47 pF
Watchdog Timeout Period
–6–
Watchdog Output (WDO)
The Watchdog Output WDO provides a status output which
goes low if the watchdog timer “times out” and remains low
until set high by the next transition on the watchdog input.
WDO is also set high when LL
Figure 4d. Internal Oscillator (100 ms Watchdog)
Figure 4c. Internal Oscillator (1.6 s Watchdog)
Immediately After Reset
4096 CLKS
1.6 s
1.6 s
1.6 s
NC
NC
NC
OSC
C/47 pF
Figure 4b. External Capacitor
(Hz) = 184,000/C (pF).
C
OSC
8
7
8
7
8
7
OSC IN
OSC IN
OSC SEL
OSC SEL
IN
OSC IN
OSC SEL
goes below the reset threshold.
ADM69x
ADM69x
ADM69x
Reset Active Period
512 CLKS
200 ms
50 ms
50 ms
C/47 pF
REV. 0