LTC699IS8 데이터 시트보기 (PDF) - Linear Technology
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LTC699IS8 Datasheet PDF : 4 Pages
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LTC699
APPLICATI S I FOR ATIO
V2
VCC
V1
V2
V1 = RESET VOLTAGE THRESHOLD
V1
V2 = RESET VOLTAGE THRESHOLD +
RESET THRESHOLD HYSTERESIS
RESET
t1
t1
t1 = RESET ACTIVE TIME
Figure 1. Reset Active Time
LTC699 F01
Watchdog Timer
The LTC699 provides a watchdog timer function to moni-
tor the activity of the microprocessor. If the microproces-
sor does not toggle the Watchdog Input (WDI) within the
time-out period, RESET is forced to active low for a
minimum of 140ms. The watchdog time-out period is
fixed at a 1.0 second minimum on the LTC699, which is
adequate time for most systems to service the watchdog
timer immediately after a reset. Figure 2 shows the timing
diagram of watchdog time-out period and reset active
time. The watchdog time-out period is restarted as soon
VCC = 5V
as RESET is inactive. When either a high-to-low or low-to-
high transition occurs at the WDI pin prior to time-out, the
watchdog time is reset and begins to time out again. To
ensure the watchdog time does not time out, either a high-
to-low or low-to-high transition on the WDI pin must
occur at or less than the minimum time-out period. If the
input to the WDI pin remains either high or low, reset
pulses will be issued every 1.6 seconds typically. The
watchdog time can be deactivated by floating the WDI pin.
The timer is also disabled when VCC falls below the reset
voltage threshold.
WDI
t2
t2
RESET
t1
t1
t1
t1 = RESET ACTIVE TIME
t2 = WATCHDOG TIME-OUT PERIOD
Figure 2. Watchdog Time-Out Period and Reset Active Time
LTC699 F02
PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted.
N8 Package
8-Lead Plastic DIP
E
B1
D
87 65
A
Q1
E1
C
eA
S
L A1
1
e1
B
SYMBOL INCHES
A
0.130 ± 0.006
A1
0.020 MIN
B
0.018 ± 0.003
B1
0.045 – 0.065
C
0.009 – 0.015
D
0.400 MAX
E
0.300 – 0.320
MILLIMETERS
3.302 ± 0.127
0.508 MIN
0.457 ± 0.076
1.143 – 1.651
0.229 – 0.381
10.160 MAX
7.620 – 8.128
SYMBOL INCHES
E1
0.250 ± 0.010
eA
0.325 + 0.025
–0.015
e1
0.100 ± 0.010
L
0.125 MIN
Q1
0.065 TYP
S
0.045 ± 0.015
MILLIMETERS
6.350 ± 0.254
8.255 + 0.635
–0.381
2.540 ± 0.254
3.175 MIN
1.651 TYP
1.143 ± 0.381
2 34
N8 1191
TJMAX
θJA
110°C 130°C/W
S8 Package
8-Lead Plastic SOIC
h × 45°
CA
8
A1
B
e1
H
α
L
SYMBOL INCHES
MILLIMETERS SYMBOL INCHES
MILLIMETERS
A
0.053 – 0.069 1.346 – 1.753 e
0.050 TYP 1.270 TYP
A1
0.004 – 0.010 0.102 – 0.254 H
0.228 – 0.244 5.791 – 6.198
B
0.014 – 0.019 0.356 – 0.483 h
0.010 – 0.020 0.254 – 0.508
1
C
0.008 – 0.010 0.203 – 0.254 L
0.016 – 0.050 0.406 – 1.270
D
0.189 – 0.197 4.801 – 5.004 α
0° – 8° TYP
E
0.150 – 0.157 3.810 – 3.988
TJMAX
θJA CONDITIONS: PCB MOUNT ON FR4 MATERIAL,
110°C 180°C/W STILL AIR AT 25°C, COPPER TRACE
D
7
6
5
E
2
34
S8 1191
4
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
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© LINEAR TECHNOLOGY CORPORATION 1992
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