LTC693 LINER [Linear Technology], LTC693 Datasheet - Page 13

• Manufacturer Part Number: LTC693
• Description: Microprocessor Supervisory Circuits
• Manufacturer: LINER [Linear Technology]

A
The LTC693 provides an additional output (Watchdog
Output, WDO) which goes low if the watchdog timer is
allowed to time out and remains low until set high by the
next transition on the WDI pin. WDO is also set high when
V
The LTC693 has two additonal pins OSC SEL and OSC IN,
which allow reset active time and watchdog time-out
period to be adjusted per Table 2. Several configurations
are shown in Figure 12.
OSC IN can be driven by an external clock signal or an
external capacitor can be connected between OSC IN and
CC
PPLICATI
falls below the reset voltage threshold or V
RESET
WDO
V
WDI
CC
O
= 5V
U
S
5V
5V
I FOR ATIO
U
4
4
3
3
1.6 SECOND WATCHDOG
INTERNAL OSCILLATOR
V
GND
GND
V
t1
EXTERNAL CLOCK
CC
CC
Figure 11. Watchdog Time-out Period and Reset Active Time
LTC693
LTC693
W
OSC SEL
OSC SEL
OSC IN
OSC IN
t2
Figure 12. Oscillator Configurations
7
8
8
7
BATT
FLOATING
OR HIGH
FLOATING
OR HIGH
U
.
t1
t1 = RESET ACTIVE TIME
t2 = NORMAL WATCHDOG TIME-OUT PERIOD
t3 = WATCHDOG TIME-OUT PERIOD IMMEDIATELY
AFTER A RESET
GND when OSC SEL is forced low. In these configurations,
the nominal reset active time and watchdog time-out
period are determined by the number of clocks or set by
the formula in Table 2. When OSC SEL is high or floating,
the internal oscillator is enabled and the reset active time
is fixed at 140ms minimum. OSC IN selects between the
1 second and 70ms minimum normal watchdog time-out
periods. In both cases, the time-out period immediately
after a reset is at least 1 second.
t3
5V
5V
3
4
4
3
EXTERNAL OSCILLATOR
INTERNAL OSCILLATOR
100ms WATCHDOG
V
GND
V
GND
CC
CC
LTC693
LTC693
OSC SEL
OSC SEL
OSC IN
OSC IN
8
7
8
7
LTC692/LTC693
FLOATING
OR HIGH
LTC692/3 • F12
LTC692/3 • F11
13