LTC695-3.3 LINER [Linear Technology], LTC695-3.3 Datasheet - Page 13

• Manufacturer Part Number: LTC695-3.3
• Description: 3.3V Microprocessor Supervisory Circuits
• Manufacturer: LINER [Linear Technology]

A
The LTC695-3.3 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 LTC695-3.3 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.
CC
PPLICATI
falls below the reset voltage threshold or V
RESET
V
WDO
CC
WDI
O
= 3.3V
U
3.3V
S
3.3V
I FOR ATIO
U
4
4
3
3
1.6 SECOND WATCHDOG
INTERNAL OSCILLATOR
V
GND
GND
V
EXTERNAL CLOCK
CC
CC
LTC695-3.3
t
Figure 11. Watchdog Time-Out Period and Reset Active Time
LTC695-3.3
1
W
OSC SEL
OSC SEL
OSC IN
OSC IN
Figure 12. Oscillator Configurations
8
7
7
8
t
2
FLOATING
OR HIGH
FLOATING
OR HIGH
BATT
U
.
t
1
t
t
t
1
2
3
= RESET ACTIVE TIME
= NORMAL WATCHDOG TIME-OUT PERIOD
= WATCHDOG TIME-OUT PERIOD IMMEDIATELY
AFTER A RESET
OSC IN can be driven by an external clock signal or an
external capacitor can be connected between OSC IN and
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 for the LTC695-3.3. 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.
3.3V
3.3V
t
3
4
3
4
3
INTERNAL OSCILLATOR
EXTERNAL OSCILLATOR
100ms WATCHDOG
V
GND
V
GND
LTC694-3.3/LTC695-3.3
CC
CC
LTC695-3.3
LTC695-3.3
OSC SEL
OSC SEL
OSC IN
OSC IN
8
7
8
7
FLOATING
OR HIGH
694/5-3.3 F12
694/5-3.3 F11
13