ltc693csw-trpbf Linear Technology Corporation, ltc693csw-trpbf Datasheet - Page 15

• Manufacturer Part Number: ltc693csw-trpbf
• Description: Microprocessor Supervisory Circuits
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
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 con-
fi gurations 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
Table 2. LTC693 Reset Active Time and Watchdog Time-Out Selections
*The nominal internal frequency is 10.24kHz. The nominal oscillator frequency with external capacitor is f
CC
falls below the reset voltage threshold or V
Floating or High
Floating or High
OSC SEL
Low
Low
5V
5V
4
4
3
3
1.6 SECOND WATCHDOG
INTERNAL OSCILLATOR
V
GND
GND
External Clock Input
V
EXTERNAL CLOCK
External Capacitor*
CC
CC
Floating or High
LTC693
LTC693
OSC IN
Low
OSC SEL
OSC SEL
OSC IN
OSC IN
8
7
7
8
Figure 12. Oscillator Confi gurations
FLOATING
OR HIGH
FLOATING
OR HIGH
BATT
NORMAL (SHORT PERIOD)
.
400ms
1024 clks
47pF
100ms
1.6 sec
WATCHDOG TIME-OUT PERIOD
GND when OSC SEL is forced low. In these confi gurations,
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 fl oating,
the internal oscillator is enabled and the reset active time
is fi xed 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.
C
5V
5V
3
4
4
3
EXTERNAL OSCILLATOR
INTERNAL OSCILLATOR
IMMEDIATELY AFTER RESET
100ms WATCHDOG
V
GND
V
GND
CC
CC
LTC693
LTC693
(LONG PERIOD)
1.6 sec
OSC SEL
OSC SEL
4096 clks
47pF
1.6 sec
1.6 sec
OSC IN
OSC IN
OSC
(Hz) =
8
7
C
LTC692/LTC693
8
7
184,000
FLOATING
OR HIGH
C (pF)
692_3 • F12
RESET ACTIVE TIME
800ms
2048 clks
47pF
LTC693
200ms
200ms
C
15
0692fa